# Changelog: 2023

This changelog documents all esbuild versions published in the year 2023 (versions 0.16.13 through 0.19.11).

## 0.19.11

* Fix TypeScript-specific class transform edge case ([#3559](https://github.com/evanw/esbuild/issues/3559))

    The previous release introduced an optimization that avoided transforming `super()` in the class constructor for TypeScript code compiled with `useDefineForClassFields` set to `false` if all class instance fields have no initializers. The rationale was that in this case, all class instance fields are omitted in the output so no changes to the constructor are needed. However, if all of this is the case _and_ there are `#private` instance fields with initializers, those private instance field initializers were still being moved into the constructor. This was problematic because they were being inserted before the call to `super()` (since `super()` is now no longer transformed in that case). This release introduces an additional optimization that avoids moving the private instance field initializers into the constructor in this edge case, which generates smaller code, matches the TypeScript compiler's output more closely, and avoids this bug:

    ```ts
    // Original code
    class Foo extends Bar {
      #private = 1;
      public: any;
      constructor() {
        super();
      }
    }

    // Old output (with esbuild v0.19.9)
    class Foo extends Bar {
      constructor() {
        super();
        this.#private = 1;
      }
      #private;
    }

    // Old output (with esbuild v0.19.10)
    class Foo extends Bar {
      constructor() {
        this.#private = 1;
        super();
      }
      #private;
    }

    // New output
    class Foo extends Bar {
      #private = 1;
      constructor() {
        super();
      }
    }
    ```

* Minifier: allow reording a primitive past a side-effect ([#3568](https://github.com/evanw/esbuild/issues/3568))

    The minifier previously allowed reordering a side-effect past a primitive, but didn't handle the case of reordering a primitive past a side-effect. This additional case is now handled:

    ```js
    // Original code
    function f() {
      let x = false;
      let y = x;
      const boolean = y;
      let frag = $.template(`<p contenteditable="${boolean}">hello world</p>`);
      return frag;
    }

    // Old output (with --minify)
    function f(){const e=!1;return $.template(`<p contenteditable="${e}">hello world</p>`)}

    // New output (with --minify)
    function f(){return $.template('<p contenteditable="false">hello world</p>')}
    ```

* Minifier: consider properties named using known `Symbol` instances to be side-effect free ([#3561](https://github.com/evanw/esbuild/issues/3561))

    Many things in JavaScript can have side effects including property accesses and ToString operations, so using a symbol such as `Symbol.iterator` as a computed property name is not obviously side-effect free. This release adds a special case for known `Symbol` instances so that they are considered side-effect free when used as property names. For example, this class declaration will now be considered side-effect free:

    ```js
    class Foo {
      *[Symbol.iterator]() {
      }
    }
    ```

* Provide the `stop()` API in node to exit esbuild's child process ([#3558](https://github.com/evanw/esbuild/issues/3558))

    You can now call `stop()` in esbuild's node API to exit esbuild's child process to reclaim the resources used. It only makes sense to do this for a long-lived node process when you know you will no longer be making any more esbuild API calls. It is not necessary to call this to allow node to exit, and it's advantageous to not call this in between calls to esbuild's API as sharing a single long-lived esbuild child process is more efficient than re-creating a new esbuild child process for every API call. This API call used to exist but was removed in [version 0.9.0](https://github.com/evanw/esbuild/releases/v0.9.0). This release adds it back due to a user request.

## 0.19.10

* Fix glob imports in TypeScript files ([#3319](https://github.com/evanw/esbuild/issues/3319))

    This release fixes a problem where bundling a TypeScript file containing a glob import could emit a call to a helper function that doesn't exist. The problem happened because esbuild's TypeScript transformation removes unused imports (which is required for correctness, as they may be type-only imports) and esbuild's glob import transformation wasn't correctly marking the imported helper function as used. This wasn't caught earlier because most of esbuild's glob import tests were written in JavaScript, not in TypeScript.

* Fix `require()` glob imports with bundling disabled ([#3546](https://github.com/evanw/esbuild/issues/3546))

    Previously `require()` calls containing glob imports were incorrectly transformed when bundling was disabled. All glob imports should only be transformed when bundling is enabled. This bug has been fixed.

* Fix a panic when transforming optional chaining with `define` ([#3551](https://github.com/evanw/esbuild/issues/3551), [#3554](https://github.com/evanw/esbuild/pull/3554))

    This release fixes a case where esbuild could crash with a panic, which was triggered by using `define` to replace an expression containing an optional chain. Here is an example:

    ```js
    // Original code
    console.log(process?.env.SHELL)

    // Old output (with --define:process.env={})
    /* panic: Internal error (while parsing "<stdin>") */

    // New output (with --define:process.env={})
    var define_process_env_default = {};
    console.log(define_process_env_default.SHELL);
    ```

    This fix was contributed by [@hi-ogawa](https://github.com/hi-ogawa).

* Work around a bug in node's CommonJS export name detector ([#3544](https://github.com/evanw/esbuild/issues/3544))

    The export names of a CommonJS module are dynamically-determined at run time because CommonJS exports are properties on a mutable object. But the export names of an ES module are statically-determined at module instantiation time by using `import` and `export` syntax and cannot be changed at run time.

    When you import a CommonJS module into an ES module in node, node scans over the source code to attempt to detect the set of export names that the CommonJS module will end up using. That statically-determined set of names is used as the set of names that the ES module is allowed to import at module instantiation time. However, this scan appears to have bugs (or at least, can cause false positives) because it doesn't appear to do any scope analysis. Node will incorrectly consider the module to export something even if the assignment is done to a local variable instead of to the module-level `exports` object. For example:

    ```js
    // confuseNode.js
    exports.confuseNode = function(exports) {
      // If this local is called "exports", node incorrectly
      // thinks this file has an export called "notAnExport".
      exports.notAnExport = function() {
      };
    };
    ```

    You can see that node incorrectly thinks the file `confuseNode.js` has an export called `notAnExport` when that file is loaded in an ES module context:

    ```console
    $ node -e 'import("./confuseNode.js").then(console.log)'
    [Module: null prototype] {
      confuseNode: [Function (anonymous)],
      default: { confuseNode: [Function (anonymous)] },
      notAnExport: undefined
    }
    ```

    To avoid this, esbuild will now rename local variables that use the names `exports` and `module` when generating CommonJS output for the `node` platform.

* Fix the return value of esbuild's `super()` shim ([#3538](https://github.com/evanw/esbuild/issues/3538))

    Some people write `constructor` methods that use the return value of `super()` instead of using `this`. This isn't too common because [TypeScript doesn't let you do that](https://github.com/microsoft/TypeScript/issues/37847) but it can come up when writing JavaScript. Previously esbuild's class lowering transform incorrectly transformed the return value of `super()` into `undefined`. With this release, the return value of `super()` will now be `this` instead:

    ```js
    // Original code
    class Foo extends Object {
      field
      constructor() {
        console.log(typeof super())
      }
    }
    new Foo

    // Old output (with --target=es6)
    class Foo extends Object {
      constructor() {
        var __super = (...args) => {
          super(...args);
          __publicField(this, "field");
        };
        console.log(typeof __super());
      }
    }
    new Foo();

    // New output (with --target=es6)
    class Foo extends Object {
      constructor() {
        var __super = (...args) => {
          super(...args);
          __publicField(this, "field");
          return this;
        };
        console.log(typeof __super());
      }
    }
    new Foo();
    ```

* Terminate the Go GC when esbuild's `stop()` API is called ([#3552](https://github.com/evanw/esbuild/issues/3552))

    If you use esbuild with WebAssembly and pass the `worker: false` flag to `esbuild.initialize()`, then esbuild will run the WebAssembly module on the main thread. If you do this within a Deno test and that test calls `esbuild.stop()` to clean up esbuild's resources, Deno may complain that a `setTimeout()` call lasted past the end of the test. This happens when the Go is in the middle of a garbage collection pass and has scheduled additional ongoing garbage collection work. Normally calling `esbuild.stop()` will terminate the web worker that the WebAssembly module runs in, which will terminate the Go GC, but that doesn't happen if you disable the web worker with `worker: false`.

    With this release, esbuild will now attempt to terminate the Go GC in this edge case by calling `clearTimeout()` on these pending timeouts.

* Apply `/* @__NO_SIDE_EFFECTS__ */` on tagged template literals ([#3511](https://github.com/evanw/esbuild/issues/3511))

    Tagged template literals that reference functions annotated with a `@__NO_SIDE_EFFECTS__` comment are now able to be removed via tree-shaking if the result is unused. This is a convention from [Rollup](https://github.com/rollup/rollup/pull/5024). Here is an example:

    ```js
    // Original code
    const html = /* @__NO_SIDE_EFFECTS__ */ (a, ...b) => ({ a, b })
    html`<a>remove</a>`
    x = html`<b>keep</b>`

    // Old output (with --tree-shaking=true)
    const html = /* @__NO_SIDE_EFFECTS__ */ (a, ...b) => ({ a, b });
    html`<a>remove</a>`;
    x = html`<b>keep</b>`;

    // New output (with --tree-shaking=true)
    const html = /* @__NO_SIDE_EFFECTS__ */ (a, ...b) => ({ a, b });
    x = html`<b>keep</b>`;
    ```

    Note that this feature currently only works within a single file, so it's not especially useful. This feature does not yet work across separate files. I still recommend using `@__PURE__` annotations instead of this feature, as they have wider tooling support. The drawback of course is that `@__PURE__` annotations need to be added at each call site, not at the declaration, and for non-call expressions such as template literals you need to wrap the expression in an IIFE (immediately-invoked function expression) to create a call expression to apply the `@__PURE__` annotation to.

* Publish builds for IBM AIX PowerPC 64-bit ([#3549](https://github.com/evanw/esbuild/issues/3549))

    This release publishes a binary executable to npm for IBM AIX PowerPC 64-bit, which means that in theory esbuild can now be installed in that environment with `npm install esbuild`. This hasn't actually been tested yet. If you have access to such a system, it would be helpful to confirm whether or not doing this actually works.

## 0.19.9

* Add support for transforming new CSS gradient syntax for older browsers

    The specification called [CSS Images Module Level 4](https://www.w3.org/TR/css-images-4/) introduces new CSS gradient syntax for customizing how the browser interpolates colors in between color stops. You can now control the color space that the interpolation happens in as well as (for "polar" color spaces) control whether hue angle interpolation happens clockwise or counterclockwise. You can read more about this in [Mozilla's blog post about new CSS gradient features](https://developer.mozilla.org/en-US/blog/css-color-module-level-4/).

    With this release, esbuild will now automatically transform this syntax for older browsers in the `target` list. For example, here's a gradient that should appear as a rainbow in a browser that supports this new syntax:

    ```css
    /* Original code */
    .rainbow-gradient {
      width: 100px;
      height: 100px;
      background: linear-gradient(in hsl longer hue, #7ff, #77f);
    }

    /* New output (with --target=chrome99) */
    .rainbow-gradient {
      width: 100px;
      height: 100px;
      background:
        linear-gradient(
          #77ffff,
          #77ffaa 12.5%,
          #77ff80 18.75%,
          #84ff77 21.88%,
          #99ff77 25%,
          #eeff77 37.5%,
          #fffb77 40.62%,
          #ffe577 43.75%,
          #ffbb77 50%,
          #ff9077 56.25%,
          #ff7b77 59.38%,
          #ff7788 62.5%,
          #ff77dd 75%,
          #ff77f2 78.12%,
          #f777ff 81.25%,
          #cc77ff 87.5%,
          #7777ff);
    }
    ```

    You can now use this syntax in your CSS source code and esbuild will automatically convert it to an equivalent gradient for older browsers. In addition, esbuild will now also transform "double position" and "transition hint" syntax for older browsers as appropriate:

    ```css
    /* Original code */
    .stripes {
      width: 100px;
      height: 100px;
      background: linear-gradient(#e65 33%, #ff2 33% 67%, #99e 67%);
    }
    .glow {
      width: 100px;
      height: 100px;
      background: radial-gradient(white 10%, 20%, black);
    }

    /* New output (with --target=chrome33) */
    .stripes {
      width: 100px;
      height: 100px;
      background:
        linear-gradient(
          #e65 33%,
          #ff2 33%,
          #ff2 67%,
          #99e 67%);
    }
    .glow {
      width: 100px;
      height: 100px;
      background:
        radial-gradient(
          #ffffff 10%,
          #aaaaaa 12.81%,
          #959595 15.62%,
          #7b7b7b 21.25%,
          #5a5a5a 32.5%,
          #444444 43.75%,
          #323232 55%,
          #161616 77.5%,
          #000000);
    }
    ```

    You can see visual examples of these new syntax features by looking at [esbuild's gradient transformation tests](https://esbuild.github.io/gradient-tests/).

    If necessary, esbuild will construct a new gradient that approximates the original gradient by recursively splitting the interval in between color stops until the approximation error is within a small threshold. That is why the above output CSS contains many more color stops than the input CSS.

    Note that esbuild deliberately _replaces_ the original gradient with the approximation instead of inserting the approximation before the original gradient as a fallback. The latest version of Firefox has multiple gradient rendering bugs (including incorrect interpolation of partially-transparent colors and interpolating non-sRGB colors using the incorrect color space). If esbuild didn't replace the original gradient, then Firefox would use the original gradient instead of the fallback the appearance would be incorrect in Firefox. In other words, the latest version of Firefox supports modern gradient syntax but interprets it incorrectly.

* Add support for `color()`, `lab()`, `lch()`, `oklab()`, `oklch()`, and `hwb()` in CSS

    CSS has recently added lots of new ways of specifying colors. You can read more about this in [Chrome's blog post about CSS color spaces](https://developer.chrome.com/docs/css-ui/high-definition-css-color-guide).

    This release adds support for minifying colors that use the `color()`, `lab()`, `lch()`, `oklab()`, `oklch()`, or `hwb()` syntax and/or transforming these colors for browsers that don't support it yet:

    ```css
    /* Original code */
    div {
      color: hwb(90deg 20% 40%);
      background: color(display-p3 1 0 0);
    }

    /* New output (with --target=chrome99) */
    div {
      color: #669933;
      background: #ff0f0e;
      background: color(display-p3 1 0 0);
    }
    ```

    As you can see, colors outside of the sRGB color space such as `color(display-p3 1 0 0)` are mapped back into the sRGB gamut and inserted as a fallback for browsers that don't support the new color syntax.

* Allow empty type parameter lists in certain cases ([#3512](https://github.com/evanw/esbuild/issues/3512))

    TypeScript allows interface declarations and type aliases to have empty type parameter lists. Previously esbuild didn't handle this edge case but with this release, esbuild will now parse this syntax:

    ```ts
    interface Foo<> {}
    type Bar<> = {}
    ```

    This fix was contributed by [@magic-akari](https://github.com/magic-akari).

## 0.19.8

* Add a treemap chart to esbuild's bundle analyzer ([#2848](https://github.com/evanw/esbuild/issues/2848))

    The bundler analyzer on esbuild's website (https://esbuild.github.io/analyze/) now has a treemap chart type in addition to the two existing chart types (sunburst and flame). This should be more familiar for people coming from other similar tools, as well as make better use of large screens.

* Allow decorators after the `export` keyword ([#104](https://github.com/evanw/esbuild/issues/104))

    Previously esbuild's decorator parser followed the original behavior of TypeScript's experimental decorators feature, which only allowed decorators to come before the `export` keyword. However, the upcoming JavaScript decorators feature also allows decorators to come after the `export` keyword. And with TypeScript 5.0, TypeScript now also allows experimental decorators to come after the `export` keyword too. So esbuild now allows this as well:

    ```js
    // This old syntax has always been permitted:
    @decorator export class Foo {}
    @decorator export default class Foo {}

    // This new syntax is now permitted too:
    export @decorator class Foo {}
    export default @decorator class Foo {}
    ```

    In addition, esbuild's decorator parser has been rewritten to fix several subtle and likely unimportant edge cases with esbuild's parsing of exports and decorators in TypeScript (e.g. TypeScript apparently does automatic semicolon insertion after `interface` and `export interface` but not after `export default interface`).

* Pretty-print decorators using the same whitespace as the original

    When printing code containing decorators, esbuild will now try to respect whether the original code contained newlines after the decorator or not. This can make generated code containing many decorators much more compact to read:

    ```js
    // Original code
    class Foo {
      @a @b @c abc
      @x @y @z xyz
    }

    // Old output
    class Foo {
      @a
      @b
      @c
      abc;
      @x
      @y
      @z
      xyz;
    }

    // New output
    class Foo {
      @a @b @c abc;
      @x @y @z xyz;
    }
    ```

## 0.19.7

* Add support for bundling code that uses import attributes ([#3384](https://github.com/evanw/esbuild/issues/3384))

    JavaScript is gaining new syntax for associating a map of string key-value pairs with individual ESM imports. The proposal is still a work in progress and is still undergoing significant changes before being finalized. However, the first iteration has already been shipping in Chromium-based browsers for a while, and the second iteration has landed in V8 and is now shipping in node, so it makes sense for esbuild to support it. Here are the two major iterations of this proposal (so far):

    1. Import assertions (deprecated, will not be standardized)
        * Uses the `assert` keyword
        * Does _not_ affect module resolution
        * Causes an error if the assertion fails
        * Shipping in Chrome 91+ (and in esbuild 0.11.22+)

    2. Import attributes (currently set to become standardized)
        * Uses the `with` keyword
        * Affects module resolution
        * Unknown attributes cause an error
        * Shipping in node 21+

    You can already use esbuild to bundle code that uses import assertions (the first iteration). However, this feature is mostly useless for bundlers because import assertions are not allowed to affect module resolution. It's basically only useful as an annotation on external imports, which esbuild will then preserve in the output for use in a browser (which would otherwise refuse to load certain imports).

    With this release, esbuild now supports bundling code that uses import attributes (the second iteration). This is much more useful for bundlers because they are allowed to affect module resolution, which means the key-value pairs can be provided to plugins. Here's an example, which uses esbuild's built-in support for the upcoming [JSON module standard](https://github.com/tc39/proposal-json-modules):

    ```js
    // On static imports
    import foo from './package.json' with { type: 'json' }
    console.log(foo)

    // On dynamic imports
    const bar = await import('./package.json', { with: { type: 'json' } })
    console.log(bar)
    ```

    One important consequence of the change in semantics between import assertions and import attributes is that two imports with identical paths but different import attributes are now considered to be different modules. This is because the import attributes are provided to the loader, which might then use those attributes during loading. For example, you could imagine an image loader that produces an image of a different size depending on the import attributes.

    Import attributes are now reported in the [metafile](https://esbuild.github.io/api/#metafile) and are now provided to [on-load plugins](https://esbuild.github.io/plugins/#on-load) as a map in the `with` property. For example, here's an esbuild plugin that turns all imports with a `type` import attribute equal to `'cheese'` into a module that exports the cheese emoji:

    ```js
    const cheesePlugin = {
      name: 'cheese',
      setup(build) {
        build.onLoad({ filter: /.*/ }, args => {
          if (args.with.type === 'cheese') return {
            contents: `export default "🧀"`,
          }
        })
      }
    }

    require('esbuild').build({
      bundle: true,
      write: false,
      stdin: {
        contents: `
          import foo from 'data:text/javascript,' with { type: 'cheese' }
          console.log(foo)
        `,
      },
      plugins: [cheesePlugin],
    }).then(result => {
      const code = new Function(result.outputFiles[0].text)
      code()
    })
    ```

    Warning: It's possible that the second iteration of this feature may change significantly again even though it's already shipping in real JavaScript VMs (since it has already happened once before). In that case, esbuild may end up adjusting its implementation to match the eventual standard behavior. So keep in mind that by using this, you are using an unstable upcoming JavaScript feature that may undergo breaking changes in the future.

* Adjust TypeScript experimental decorator behavior ([#3230](https://github.com/evanw/esbuild/issues/3230), [#3326](https://github.com/evanw/esbuild/issues/3326), [#3394](https://github.com/evanw/esbuild/issues/3394))

    With this release, esbuild will now allow TypeScript experimental decorators to access both static class properties and `#private` class names. For example:

    ```js
    const check =
      <T,>(a: T, b: T): PropertyDecorator =>
        () => console.log(a === b)

    async function test() {
      class Foo {
        static #foo = 1
        static bar = 1 + Foo.#foo
        @check(Foo.#foo, 1) a: any
        @check(Foo.bar, await Promise.resolve(2)) b: any
      }
    }

    test().then(() => console.log('pass'))
    ```

    This will now print `true true pass` when compiled by esbuild. Previously esbuild evaluated TypeScript decorators outside of the class body, so it didn't allow decorators to access `Foo` or `#foo`. Now esbuild does something different, although it's hard to concisely explain exactly what esbuild is doing now (see the background section below for more information).

    Note that TypeScript's experimental decorator support is currently buggy: TypeScript's compiler passes this test if only the first `@check` is present or if only the second `@check` is present, but TypeScript's compiler fails this test if both checks are present together. I haven't changed esbuild to match TypeScript's behavior exactly here because I'm waiting for TypeScript to fix these bugs instead.

    Some background: TypeScript experimental decorators don't have consistent semantics regarding the context that the decorators are evaluated in. For example, TypeScript will let you use `await` within a decorator, which implies that the decorator runs outside the class body (since `await` isn't supported inside a class body), but TypeScript will also let you use `#private` names, which implies that the decorator runs inside the class body (since `#private` names are only supported inside a class body). The value of `this` in a decorator is also buggy (the run-time value of `this` changes if any decorator in the class uses a `#private` name but the type of `this` doesn't change, leading to the type checker no longer matching reality). These inconsistent semantics make it hard for esbuild to implement this feature as decorator evaluation happens in some superposition of both inside and outside the class body that is particular to the internal implementation details of the TypeScript compiler.

* Forbid `--keep-names` when targeting old browsers ([#3477](https://github.com/evanw/esbuild/issues/3477))

    The `--keep-names` setting needs to be able to assign to the `name` property on functions and classes. However, before ES6 this property was non-configurable, and attempting to assign to it would throw an error. So with this release, esbuild will no longer allow you to enable this setting while also targeting a really old browser.

## 0.19.6

* Fix a constant folding bug with bigint equality

    This release fixes a bug where esbuild incorrectly checked for bigint equality by checking the equality of the bigint literal text. This is correct if the bigint doesn't have a radix because bigint literals without a radix are always in canonical form (since leading zeros are not allowed). However, this is incorrect if the bigint has a radix (e.g. `0x123n`) because the canonical form is not enforced when a radix is present.

    ```js
    // Original code
    console.log(!!0n, !!1n, 123n === 123n)
    console.log(!!0x0n, !!0x1n, 123n === 0x7Bn)

    // Old output
    console.log(false, true, true);
    console.log(true, true, false);

    // New output
    console.log(false, true, true);
    console.log(!!0x0n, !!0x1n, 123n === 0x7Bn);
    ```

* Add some improvements to the JavaScript minifier

    This release adds more cases to the JavaScript minifier, including support for inlining `String.fromCharCode` and `String.prototype.charCodeAt` when possible:

    ```js
    // Original code
    document.onkeydown = e => e.keyCode === 'A'.charCodeAt(0) && console.log(String.fromCharCode(55358, 56768))

    // Old output (with --minify)
    document.onkeydown=o=>o.keyCode==="A".charCodeAt(0)&&console.log(String.fromCharCode(55358,56768));

    // New output (with --minify)
    document.onkeydown=o=>o.keyCode===65&&console.log("🧀");
    ```

    In addition, immediately-invoked function expressions (IIFEs) that return a single expression are now inlined when minifying. This makes it possible to use IIFEs in combination with `@__PURE__` annotations to annotate arbitrary expressions as side-effect free without the IIFE wrapper impacting code size. For example:

    ```js
    // Original code
    const sideEffectFreeOffset = /* @__PURE__ */ (() => computeSomething())()
    use(sideEffectFreeOffset)

    // Old output (with --minify)
    const e=(()=>computeSomething())();use(e);

    // New output (with --minify)
    const e=computeSomething();use(e);
    ```

* Automatically prefix the `mask-composite` CSS property for WebKit ([#3493](https://github.com/evanw/esbuild/issues/3493))

    The `mask-composite` property will now be prefixed as `-webkit-mask-composite` for older WebKit-based browsers. In addition to prefixing the property name, handling older browsers also requires rewriting the values since WebKit uses non-standard names for the mask composite modes:

    ```css
    /* Original code */
    div {
      mask-composite: add, subtract, intersect, exclude;
    }

    /* New output (with --target=chrome100) */
    div {
      -webkit-mask-composite:
        source-over,
        source-out,
        source-in,
        xor;
      mask-composite:
        add,
        subtract,
        intersect,
        exclude;
    }
    ```

* Avoid referencing `this` from JSX elements in derived class constructors ([#3454](https://github.com/evanw/esbuild/issues/3454))

    When you enable `--jsx=automatic` and `--jsx-dev`, the JSX transform is supposed to insert `this` as the last argument to the `jsxDEV` function. I'm not sure exactly why this is and I can't find any specification for it, but in any case this causes the generated code to crash when you use a JSX element in a derived class constructor before the call to `super()` as `this` is not allowed to be accessed at that point. For example

    ```js
    // Original code
    class ChildComponent extends ParentComponent {
      constructor() {
        super(<div />)
      }
    }

    // Problematic output (with --loader=jsx --jsx=automatic --jsx-dev)
    import { jsxDEV } from "react/jsx-dev-runtime";
    class ChildComponent extends ParentComponent {
      constructor() {
        super(/* @__PURE__ */ jsxDEV("div", {}, void 0, false, {
          fileName: "<stdin>",
          lineNumber: 3,
          columnNumber: 15
        }, this)); // The reference to "this" crashes here
      }
    }
    ```

    The TypeScript compiler doesn't handle this at all while the Babel compiler just omits `this` for the entire constructor (even after the call to `super()`). There seems to be no specification so I can't be sure that this change doesn't break anything important. But given that Babel is pretty loose with this and TypeScript doesn't handle this at all, I'm guessing this value isn't too important. React's blog post seems to indicate that this value was intended to be used for a React-specific migration warning at some point, so it could even be that this value is irrelevant now. Anyway the crash in this case should now be fixed.

* Allow package subpath imports to map to node built-ins ([#3485](https://github.com/evanw/esbuild/issues/3485))

    You are now able to use a [subpath import](https://nodejs.org/api/packages.html#subpath-imports) in your package to resolve to a node built-in module. For example, with a `package.json` file like this:

    ```json
    {
      "type": "module",
      "imports": {
        "#stream": {
          "node": "stream",
          "default": "./stub.js"
        }
      }
    }
    ```

    You can now import from node's `stream` module like this:

    ```js
    import * as stream from '#stream';
    console.log(Object.keys(stream));
    ```

    This will import from node's `stream` module when the platform is `node` and from `./stub.js` otherwise.

* No longer throw an error when a `Symbol` is missing ([#3453](https://github.com/evanw/esbuild/issues/3453))

    Certain JavaScript syntax features use special properties on the global `Symbol` object. For example, the asynchronous iteration syntax uses `Symbol.asyncIterator`. Previously esbuild's generated code for older browsers required this symbol to be polyfilled. However, starting with this release esbuild will use [`Symbol.for()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/for) to construct these symbols if they are missing instead of throwing an error about a missing polyfill. This means your code no longer needs to include a polyfill for missing symbols as long as your code also uses `Symbol.for()` for missing symbols.

* Parse upcoming changes to TypeScript syntax ([#3490](https://github.com/evanw/esbuild/issues/3490), [#3491](https://github.com/evanw/esbuild/pull/3491))

    With this release, you can now use `from` as the name of a default type-only import in TypeScript code, as well as `of` as the name of an `await using` loop iteration variable:

    ```ts
    import type from from 'from'
    for (await using of of of) ;
    ```

    This matches similar changes in the TypeScript compiler ([#56376](https://github.com/microsoft/TypeScript/issues/56376) and [#55555](https://github.com/microsoft/TypeScript/issues/55555)) which will start allowing this syntax in an upcoming version of TypeScript. Please never actually write code like this.

    The type-only import syntax change was contributed by [@magic-akari](https://github.com/magic-akari).

## 0.19.5

* Fix a regression in 0.19.0 regarding `paths` in `tsconfig.json` ([#3354](https://github.com/evanw/esbuild/issues/3354))

    The fix in esbuild version 0.19.0 to process `tsconfig.json` aliases before the `--packages=external` setting unintentionally broke an edge case in esbuild's handling of certain `tsconfig.json` aliases where there are multiple files with the same name in different directories. This release adjusts esbuild's behavior for this edge case so that it passes while still processing aliases before `--packages=external`. Please read the linked issue for more details.

* Fix a CSS `font` property minification bug ([#3452](https://github.com/evanw/esbuild/issues/3452))

    This release fixes a bug where esbuild's CSS minifier didn't insert a space between the font size and the font family in the `font` CSS shorthand property in the edge case where the original source code didn't already have a space and the leading string token was shortened to an identifier:

    ```css
    /* Original code */
    .foo { font: 16px"Menlo"; }

    /* Old output (with --minify) */
    .foo{font:16pxMenlo}

    /* New output (with --minify) */
    .foo{font:16px Menlo}
    ```

* Fix bundling CSS with asset names containing spaces ([#3410](https://github.com/evanw/esbuild/issues/3410))

    Assets referenced via CSS `url()` tokens may cause esbuild to generate invalid output when bundling if the file name contains spaces (e.g. `url(image 2.png)`). With this release, esbuild will now quote all bundled asset references in `url()` tokens to avoid this problem. This only affects assets loaded using the `file` and `copy` loaders.

* Fix invalid CSS `url()` tokens in `@import` rules ([#3426](https://github.com/evanw/esbuild/issues/3426))

    In the future, CSS `url()` tokens may contain additional stuff after the URL. This is irrelevant today as no CSS specification does this. But esbuild previously had a bug where using these tokens in an `@import` rule resulted in malformed output. This bug has been fixed.

* Fix `browser` + `false` + `type: module` in `package.json` ([#3367](https://github.com/evanw/esbuild/issues/3367))

    The `browser` field in `package.json` allows you to map a file to `false` to have it be treated as an empty file when bundling for the browser. However, if `package.json` contains `"type": "module"` then all `.js` files will be considered ESM, not CommonJS. Importing a named import from an empty CommonJS file gives you undefined, but importing a named export from an empty ESM file is a build error. This release changes esbuild's interpretation of these files mapped to `false` in this situation from ESM to CommonJS to avoid generating build errors for named imports.

* Fix a bug in top-level await error reporting ([#3400](https://github.com/evanw/esbuild/issues/3400))

    Using `require()` on a file that contains [top-level await](https://v8.dev/features/top-level-await) is not allowed because `require()` must return synchronously and top-level await makes that impossible. You will get a build error if you try to bundle code that does this with esbuild. This release fixes a bug in esbuild's error reporting code for complex cases of this situation involving multiple levels of imports to get to the module containing the top-level await.

* Update to Unicode 15.1.0

    The character tables that determine which characters form valid JavaScript identifiers have been updated from Unicode version 15.0.0 to the newly-released Unicode version 15.1.0. I'm not putting an example in the release notes because all of the new characters will likely just show up as little squares since fonts haven't been updated yet. But you can read https://www.unicode.org/versions/Unicode15.1.0/#Summary for more information about the changes.

    This upgrade was contributed by [@JLHwung](https://github.com/JLHwung).

## 0.19.4

* Fix printing of JavaScript decorators in tricky cases ([#3396](https://github.com/evanw/esbuild/issues/3396))

    This release fixes some bugs where esbuild's pretty-printing of JavaScript decorators could incorrectly produced code with a syntax error. The problem happened because esbuild sometimes substitutes identifiers for other expressions in the pretty-printer itself, but the decision about whether to wrap the expression or not didn't account for this. Here are some examples:

    ```js
    // Original code
    import { constant } from './constants.js'
    import { imported } from 'external'
    import { undef } from './empty.js'
    class Foo {
      @constant()
      @imported()
      @undef()
      foo
    }

    // Old output (with --bundle --format=cjs --packages=external --minify-syntax)
    var import_external = require("external");
    var Foo = class {
      @123()
      @(0, import_external.imported)()
      @(void 0)()
      foo;
    };

    // New output (with --bundle --format=cjs --packages=external --minify-syntax)
    var import_external = require("external");
    var Foo = class {
      @(123())
      @((0, import_external.imported)())
      @((void 0)())
      foo;
    };
    ```

* Allow pre-release versions to be passed to `target` ([#3388](https://github.com/evanw/esbuild/issues/3388))

    People want to be able to pass version numbers for unreleased versions of node (which have extra stuff after the version numbers) to esbuild's `target` setting and have esbuild do something reasonable with them. These version strings are of course not present in esbuild's internal feature compatibility table because an unreleased version has not been released yet (by definition). With this release, esbuild will now attempt to accept these version strings passed to `target` and do something reasonable with them.

## 0.19.3

* Fix `list-style-type` with the `local-css` loader ([#3325](https://github.com/evanw/esbuild/issues/3325))

    The `local-css` loader incorrectly treated all identifiers provided to `list-style-type` as a custom local identifier. That included identifiers such as `none` which have special meaning in CSS, and which should not be treated as custom local identifiers. This release fixes this bug:

    ```css
    /* Original code */
    ul { list-style-type: none }

    /* Old output (with --loader=local-css) */
    ul {
      list-style-type: stdin_none;
    }

    /* New output (with --loader=local-css) */
    ul {
      list-style-type: none;
    }
    ```

    Note that this bug only affected code using the `local-css` loader. It did not affect code using the `css` loader.

* Avoid inserting temporary variables before `use strict` ([#3322](https://github.com/evanw/esbuild/issues/3322))

    This release fixes a bug where esbuild could incorrectly insert automatically-generated temporary variables before `use strict` directives:

    ```js
    // Original code
    function foo() {
      'use strict'
      a.b?.c()
    }

    // Old output (with --target=es6)
    function foo() {
      var _a;
      "use strict";
      (_a = a.b) == null ? void 0 : _a.c();
    }

    // New output (with --target=es6)
    function foo() {
      "use strict";
      var _a;
      (_a = a.b) == null ? void 0 : _a.c();
    }
    ```

* Adjust TypeScript `enum` output to better approximate `tsc` ([#3329](https://github.com/evanw/esbuild/issues/3329))

    TypeScript enum values can be either number literals or string literals. Numbers create a bidirectional mapping between the name and the value but strings only create a unidirectional mapping from the name to the value. When the enum value is neither a number literal nor a string literal, TypeScript and esbuild both default to treating it as a number:

    ```ts
    // Original TypeScript code
    declare const foo: any
    enum Foo {
      NUMBER = 1,
      STRING = 'a',
      OTHER = foo,
    }

    // Compiled JavaScript code (from "tsc")
    var Foo;
    (function (Foo) {
      Foo[Foo["NUMBER"] = 1] = "NUMBER";
      Foo["STRING"] = "a";
      Foo[Foo["OTHER"] = foo] = "OTHER";
    })(Foo || (Foo = {}));
    ```

    However, TypeScript does constant folding slightly differently than esbuild. For example, it may consider template literals to be string literals in some cases:

    ```ts
    // Original TypeScript code
    declare const foo = 'foo'
    enum Foo {
      PRESENT = `${foo}`,
      MISSING = `${bar}`,
    }

    // Compiled JavaScript code (from "tsc")
    var Foo;
    (function (Foo) {
      Foo["PRESENT"] = "foo";
      Foo[Foo["MISSING"] = `${bar}`] = "MISSING";
    })(Foo || (Foo = {}));
    ```

    The template literal initializer for `PRESENT` is treated as a string while the template literal initializer for `MISSING` is treated as a number. Previously esbuild treated both of these cases as a number but starting with this release, esbuild will now treat both of these cases as a string. This doesn't exactly match the behavior of `tsc` but in the case where the behavior diverges `tsc` reports a compile error, so this seems like acceptible behavior for esbuild. Note that handling these cases completely correctly would require esbuild to parse type declarations (see the `declare` keyword), which esbuild deliberately doesn't do.

* Ignore case in CSS in more places ([#3316](https://github.com/evanw/esbuild/issues/3316))

    This release makes esbuild's CSS support more case-agnostic, which better matches how browsers work. For example:

    ```css
    /* Original code */
    @KeyFrames Foo { From { OpaCity: 0 } To { OpaCity: 1 } }
    body { CoLoR: YeLLoW }

    /* Old output (with --minify) */
    @KeyFrames Foo{From {OpaCity: 0} To {OpaCity: 1}}body{CoLoR:YeLLoW}

    /* New output (with --minify) */
    @KeyFrames Foo{0%{OpaCity:0}To{OpaCity:1}}body{CoLoR:#ff0}
    ```

    Please never actually write code like this.

* Improve the error message for `null` entries in `exports` ([#3377](https://github.com/evanw/esbuild/issues/3377))

    Package authors can disable package export paths with the `exports` map in `package.json`. With this release, esbuild now has a clearer error message that points to the `null` token in `package.json` itself instead of to the surrounding context. Here is an example of the new error message:

    ```
    ✘ [ERROR] Could not resolve "msw/browser"

        lib/msw-config.ts:2:28:
          2 │ import { setupWorker } from 'msw/browser';
            ╵                             ~~~~~~~~~~~~~

      The path "./browser" cannot be imported from package "msw" because it was explicitly disabled by
      the package author here:

        node_modules/msw/package.json:17:14:
          17 │       "node": null,
             ╵               ~~~~

      You can mark the path "msw/browser" as external to exclude it from the bundle, which will remove
      this error and leave the unresolved path in the bundle.
    ```

* Parse and print the `with` keyword in `import` statements

    JavaScript was going to have a feature called "import assertions" that adds an `assert` keyword to `import` statements. It looked like this:

    ```js
    import stuff from './stuff.json' assert { type: 'json' }
    ```

    The feature provided a way to assert that the imported file is of a certain type (but was not allowed to affect how the import is interpreted, even though that's how everyone expected it to behave). The feature was fully specified and then actually implemented and shipped in Chrome before the people behind the feature realized that they should allow it to affect how the import is interpreted after all. So import assertions are no longer going to be added to the language.

    Instead, the [current proposal](https://github.com/tc39/proposal-import-attributes) is to add a feature called "import attributes" instead that adds a `with` keyword to import statements. It looks like this:

    ```js
    import stuff from './stuff.json' with { type: 'json' }
    ```

    This feature provides a way to affect how the import is interpreted. With this release, esbuild now has preliminary support for parsing and printing this new `with` keyword. The `with` keyword is not yet interpreted by esbuild, however, so bundling code with it will generate a build error. All this release does is allow you to use esbuild to process code containing it (such as removing types from TypeScript code). Note that this syntax is not yet a part of JavaScript and may be removed or altered in the future if the specification changes (which it already has once, as described above). If that happens, esbuild reserves the right to remove or alter its support for this syntax too.

## 0.19.2

* Update how CSS nesting is parsed again

    CSS nesting syntax has been changed again, and esbuild has been updated to match. Type selectors may now be used with CSS nesting:

    ```css
    .foo {
      div {
        color: red;
      }
    }
    ```

    Previously this was disallowed in the CSS specification because it's ambiguous whether an identifier is a declaration or a nested rule starting with a type selector without requiring unbounded lookahead in the parser. It has now been allowed because the CSS working group has decided that requiring unbounded lookahead is acceptable after all.

    Note that this change means esbuild no longer considers any existing browser to support CSS nesting since none of the existing browsers support this new syntax. CSS nesting will now always be transformed when targeting a browser. This situation will change in the future as browsers add support for this new syntax.

* Fix a scope-related bug with `--drop-labels=` ([#3311](https://github.com/evanw/esbuild/issues/3311))

    The recently-released `--drop-labels=` feature previously had a bug where esbuild's internal scope stack wasn't being restored properly when a statement with a label was dropped. This could manifest as a tree-shaking issue, although it's possible that this could have also been causing other subtle problems too. The bug has been fixed in this release.

* Make renamed CSS names unique across entry points ([#3295](https://github.com/evanw/esbuild/issues/3295))

    Previously esbuild's generated names for local names in CSS were only unique within a given entry point (or across all entry points when code splitting was enabled). That meant that building multiple entry points with esbuild could result in local names being renamed to the same identifier even when those entry points were built simultaneously within a single esbuild API call. This problem was especially likely to happen with minification enabled. With this release, esbuild will now avoid renaming local names from two separate entry points to the same name if those entry points were built with a single esbuild API call, even when code splitting is disabled.

* Fix CSS ordering bug with `@layer` before `@import`

    CSS lets you put `@layer` rules before `@import` rules to define the order of layers in a stylesheet. Previously esbuild's CSS bundler incorrectly ordered these after the imported files because before the introduction of cascade layers to CSS, imported files could be bundled by removing the `@import` rules and then joining files together in the right order. But with `@layer`, CSS files may now need to be split apart into multiple pieces in the bundle. For example:

    ```
    /* Original code */
    @layer start;
    @import "data:text/css,@layer inner.start;";
    @import "data:text/css,@layer inner.end;";
    @layer end;

    /* Old output (with --bundle) */
    @layer inner.start;
    @layer inner.end;
    @layer start;
    @layer end;

    /* New output (with --bundle) */
    @layer start;
    @layer inner.start;
    @layer inner.end;
    @layer end;
    ```

* Unwrap nested duplicate `@media` rules ([#3226](https://github.com/evanw/esbuild/issues/3226))

    With this release, esbuild's CSS minifier will now automatically unwrap duplicate nested `@media` rules:

    ```css
    /* Original code */
    @media (min-width: 1024px) {
      .foo { color: red }
      @media (min-width: 1024px) {
        .bar { color: blue }
      }
    }

    /* Old output (with --minify) */
    @media (min-width: 1024px){.foo{color:red}@media (min-width: 1024px){.bar{color:#00f}}}

    /* New output (with --minify) */
    @media (min-width: 1024px){.foo{color:red}.bar{color:#00f}}
    ```

    These rules are unlikely to be authored manually but may result from using frameworks such as Tailwind to generate CSS.

## 0.19.1

* Fix a regression with `baseURL` in `tsconfig.json` ([#3307](https://github.com/evanw/esbuild/issues/3307))

    The previous release moved `tsconfig.json` path resolution before `--packages=external` checks to allow the [`paths` field](https://www.typescriptlang.org/tsconfig#paths) in `tsconfig.json` to avoid a package being marked as external. However, that reordering accidentally broke the behavior of the `baseURL` field from `tsconfig.json`. This release moves these path resolution rules around again in an attempt to allow both of these cases to work.

* Parse TypeScript type arguments for JavaScript decorators ([#3308](https://github.com/evanw/esbuild/issues/3308))

    When parsing JavaScript decorators in TypeScript (i.e. with `experimentalDecorators` disabled), esbuild previously didn't parse type arguments. Type arguments will now be parsed starting with this release. For example:

    ```ts
    @foo<number>
    @bar<number, string>()
    class Foo {}
    ```

* Fix glob patterns matching extra stuff at the end ([#3306](https://github.com/evanw/esbuild/issues/3306))

    Previously glob patterns such as `./*.js` would incorrectly behave like `./*.js*` during path matching (also matching `.js.map` files, for example). This was never intentional behavior, and has now been fixed.

* Change the permissions of esbuild's generated output files ([#3285](https://github.com/evanw/esbuild/issues/3285))

    This release changes the permissions of the output files that esbuild generates to align with the default behavior of node's [`fs.writeFileSync`](https://nodejs.org/api/fs.html#fswritefilesyncfile-data-options) function. Since most tools written in JavaScript use `fs.writeFileSync`, this should make esbuild more consistent with how other JavaScript build tools behave.

    The full Unix-y details: Unix permissions use three-digit octal notation where the three digits mean "user, group, other" in that order. Within a digit, 4 means "read" and 2 means "write" and 1 means "execute". So 6 == 4 + 2 == read + write. Previously esbuild uses 0644 permissions (the leading 0 means octal notation) but the permissions for `fs.writeFileSync` defaults to 0666, so esbuild will now use 0666 permissions. This does not necessarily mean that the files esbuild generates will end up having 0666 permissions, however, as there is another Unix feature called "umask" where the operating system masks out some of these bits. If your umask is set to 0022 then the generated files will have 0644 permissions, and if your umask is set to 0002 then the generated files will have 0664 permissions.

* Fix a subtle CSS ordering issue with `@import` and `@layer`

    With this release, esbuild may now introduce additional `@layer` rules when bundling CSS to better preserve the layer ordering of the input code. Here's an example of an edge case where this matters:

    ```css
    /* entry.css */
    @import "a.css";
    @import "b.css";
    @import "a.css";
    ```

    ```css
    /* a.css */
    @layer a {
      body {
        background: red;
      }
    }
    ```

    ```css
    /* b.css */
    @layer b {
      body {
        background: green;
      }
    }
    ```

    This CSS should set the body background to `green`, which is what happens in the browser. Previously esbuild generated the following output which incorrectly sets the body background to `red`:

    ```css
    /* b.css */
    @layer b {
      body {
        background: green;
      }
    }

    /* a.css */
    @layer a {
      body {
        background: red;
      }
    }
    ```

    This difference in behavior is because the browser evaluates `a.css` + `b.css` + `a.css` (in CSS, each `@import` is replaced with a copy of the imported file) while esbuild was only writing out `b.css` + `a.css`. The first copy of `a.css` wasn't being written out by esbuild for two reasons: 1) bundlers care about code size and try to avoid emitting duplicate CSS and 2) when there are multiple copies of a CSS file, normally only the _last_ copy matters since the last declaration with equal specificity wins in CSS.

    However, `@layer` was recently added to CSS and for `@layer` the _first_ copy matters because layers are ordered using their first location in source code order. This introduction of `@layer` means esbuild needs to change its bundling algorithm. An easy solution would be for esbuild to write out `a.css` twice, but that would be inefficient. So what I'm going to try to have esbuild do with this release is to write out an abbreviated form of the first copy of a CSS file that only includes the `@layer` information, and then still only write out the full CSS file once for the last copy. So esbuild's output for this edge case now looks like this:

    ```css
    /* a.css */
    @layer a;

    /* b.css */
    @layer b {
      body {
        background: green;
      }
    }

    /* a.css */
    @layer a {
      body {
        background: red;
      }
    }
    ```

    The behavior of the bundled CSS now matches the behavior of the unbundled CSS. You may be wondering why esbuild doesn't just write out `a.css` first followed by `b.css`. That would work in this case but it doesn't work in general because for any rules outside of a `@layer` rule, the last copy should still win instead of the first copy.

* Fix a bug with esbuild's TypeScript type definitions ([#3299](https://github.com/evanw/esbuild/pull/3299))

    This release fixes a copy/paste error with the TypeScript type definitions for esbuild's JS API:

    ```diff
     export interface TsconfigRaw {
       compilerOptions?: {
    -    baseUrl?: boolean
    +    baseUrl?: string
         ...
       }
     }
    ```

    This fix was contributed by [@privatenumber](https://github.com/privatenumber).

## 0.19.0

**This release deliberately contains backwards-incompatible changes.** To avoid automatically picking up releases like this, you should either be pinning the exact version of `esbuild` in your `package.json` file (recommended) or be using a version range syntax that only accepts patch upgrades such as `^0.18.0` or `~0.18.0`. See npm's documentation about [semver](https://docs.npmjs.com/cli/v6/using-npm/semver/) for more information.

* Handle import paths containing wildcards ([#56](https://github.com/evanw/esbuild/issues/56), [#700](https://github.com/evanw/esbuild/issues/700), [#875](https://github.com/evanw/esbuild/issues/875), [#976](https://github.com/evanw/esbuild/issues/976), [#2221](https://github.com/evanw/esbuild/issues/2221), [#2515](https://github.com/evanw/esbuild/issues/2515))

    This release introduces wildcards in import paths in two places:

    * **Entry points**

        You can now pass a string containing glob-style wildcards such as `./src/*.ts` as an entry point and esbuild will search the file system for files that match the pattern. This can be used to easily pass esbuild all files with a certain extension on the command line in a cross-platform way. Previously you had to rely on the shell to perform glob expansion, but that is obviously shell-dependent and didn't work at all on Windows. Note that to use this feature on the command line you will have to quote the pattern so it's passed verbatim to esbuild without any expansion by the shell. Here's an example:

        ```sh
        esbuild --minify "./src/*.ts" --outdir=out
        ```

        Specifically the `*` character will match any character except for the `/` character, and the `/**/` character sequence will match a path separator followed by zero or more path elements. Other wildcard operators found in glob patterns such as `?` and `[...]` are not supported.

    * **Run-time import paths**

        Import paths that are evaluated at run-time can now be bundled in certain limited situations. The import path expression must be a form of string concatenation and must start with either `./` or `../`. Each non-string expression in the string concatenation chain becomes a wildcard. The `*` wildcard is chosen unless the previous character is a `/`, in which case the `/**/*` character sequence is used. Some examples:

        ```js
        // These two forms are equivalent
        const json1 = await import('./data/' + kind + '.json')
        const json2 = await import(`./data/${kind}.json`)
        ```

        This feature works with `require(...)` and `import(...)` because these can all accept run-time expressions. It does not work with `import` and `export` statements because these cannot accept run-time expressions. If you want to prevent esbuild from trying to bundle these imports, you should move the string concatenation expression outside of the `require(...)` or `import(...)`. For example:

        ```js
        // This will be bundled
        const json1 = await import('./data/' + kind + '.json')

        // This will not be bundled
        const path = './data/' + kind + '.json'
        const json2 = await import(path)
        ```

        Note that using this feature means esbuild will potentially do a lot of file system I/O to find all possible files that might match the pattern. This is by design, and is not a bug. If this is a concern, I recommend either avoiding the `/**/` pattern (e.g. by not putting a `/` before a wildcard) or using this feature only in directory subtrees which do not have many files that don't match the pattern (e.g. making a subdirectory for your JSON files and explicitly including that subdirectory in the pattern).

* Path aliases in `tsconfig.json` no longer count as packages ([#2792](https://github.com/evanw/esbuild/issues/2792), [#3003](https://github.com/evanw/esbuild/issues/3003), [#3160](https://github.com/evanw/esbuild/issues/3160), [#3238](https://github.com/evanw/esbuild/issues/3238))

    Setting `--packages=external` tells esbuild to make all import paths external when they look like a package path. For example, an import of `./foo/bar` is not a package path and won't be external while an import of `foo/bar` is a package path and will be external. However, the [`paths` field](https://www.typescriptlang.org/tsconfig#paths) in `tsconfig.json` allows you to create import paths that look like package paths but that do not resolve to packages. People do not want these paths to count as package paths. So with this release, the behavior of `--packages=external` has been changed to happen after the `tsconfig.json` path remapping step.

* Use the `local-css` loader for `.module.css` files by default ([#20](https://github.com/evanw/esbuild/issues/20))

    With this release the `css` loader is still used for `.css` files except that `.module.css` files now use the `local-css` loader. This is a common convention in the web development community. If you need `.module.css` files to use the `css` loader instead, then you can override this behavior with `--loader:.module.css=css`.

## 0.18.20

* Support advanced CSS `@import` rules ([#953](https://github.com/evanw/esbuild/issues/953), [#3137](https://github.com/evanw/esbuild/issues/3137))

    CSS `@import` statements have been extended to allow additional trailing tokens after the import path. These tokens sort of make the imported file behave as if it were wrapped in a `@layer`, `@supports`, and/or `@media` rule. Here are some examples:

    ```css
    @import url(foo.css);
    @import url(foo.css) layer;
    @import url(foo.css) layer(bar);
    @import url(foo.css) layer(bar) supports(display: flex);
    @import url(foo.css) layer(bar) supports(display: flex) print;
    @import url(foo.css) layer(bar) print;
    @import url(foo.css) supports(display: flex);
    @import url(foo.css) supports(display: flex) print;
    @import url(foo.css) print;
    ```

    You can read more about this advanced syntax [here](https://developer.mozilla.org/en-US/docs/Web/CSS/@import). With this release, esbuild will now bundle `@import` rules with these trailing tokens and will wrap the imported files in the corresponding rules. Note that this now means a given imported file can potentially appear in multiple places in the bundle. However, esbuild will still only load it once (e.g. on-load plugins will only run once per file, not once per import).

## 0.18.19

* Implement `composes` from CSS modules ([#20](https://github.com/evanw/esbuild/issues/20))

    This release implements the `composes` annotation from the [CSS modules specification](https://github.com/css-modules/css-modules#composition). It provides a way for class selectors to reference other class selectors (assuming you are using the `local-css` loader). And with the `from` syntax, this can even work with local names across CSS files. For example:

    ```js
    // app.js
    import { submit } from './style.css'
    const div = document.createElement('div')
    div.className = submit
    document.body.appendChild(div)
    ```

    ```css
    /* style.css */
    .button {
      composes: pulse from "anim.css";
      display: inline-block;
    }
    .submit {
      composes: button;
      font-weight: bold;
    }
    ```

    ```css
    /* anim.css */
    @keyframes pulse {
      from, to { opacity: 1 }
      50% { opacity: 0.5 }
    }
    .pulse {
      animation: 2s ease-in-out infinite pulse;
    }
    ```

    Bundling this with esbuild using `--bundle --outdir=dist --loader:.css=local-css` now gives the following:

    ```js
    (() => {
      // style.css
      var submit = "anim_pulse style_button style_submit";

      // app.js
      var div = document.createElement("div");
      div.className = submit;
      document.body.appendChild(div);
    })();
    ```

    ```css
    /* anim.css */
    @keyframes anim_pulse {
      from, to {
        opacity: 1;
      }
      50% {
        opacity: 0.5;
      }
    }
    .anim_pulse {
      animation: 2s ease-in-out infinite anim_pulse;
    }

    /* style.css */
    .style_button {
      display: inline-block;
    }
    .style_submit {
      font-weight: bold;
    }
    ```

    Import paths in the `composes: ... from` syntax are resolved using the new `composes-from` import kind, which can be intercepted by plugins during import path resolution when bundling is enabled.

    Note that the order in which composed CSS classes from separate files appear in the bundled output file is deliberately _**undefined**_ by design (see [the specification](https://github.com/css-modules/css-modules#composing-from-other-files) for details). You are not supposed to declare the same CSS property in two separate class selectors and then compose them together. You are only supposed to compose CSS class selectors that declare non-overlapping CSS properties.

    Issue [#20](https://github.com/evanw/esbuild/issues/20) (the issue tracking CSS modules) is esbuild's most-upvoted issue! With this change, I now consider esbuild's implementation of CSS modules to be complete. There are still improvements to make and there may also be bugs with the current implementation, but these can be tracked in separate issues.

* Fix non-determinism with `tsconfig.json` and symlinks ([#3284](https://github.com/evanw/esbuild/issues/3284))

    This release fixes an issue that could cause esbuild to sometimes emit incorrect build output in cases where a file under the effect of `tsconfig.json` is inconsistently referenced through a symlink. It can happen when using `npm link` to create a symlink within `node_modules` to an unpublished package. The build result was non-deterministic because esbuild runs module resolution in parallel and the result of the `tsconfig.json` lookup depended on whether the import through the symlink or not through the symlink was resolved first. This problem was fixed by moving the `realpath` operation before the `tsconfig.json` lookup.

* Add a `hash` property to output files ([#3084](https://github.com/evanw/esbuild/issues/3084), [#3293](https://github.com/evanw/esbuild/issues/3293))

    As a convenience, every output file in esbuild's API now includes a `hash` property that is a hash of the `contents` field. This is the hash that's used internally by esbuild to detect changes between builds for esbuild's live-reload feature. You may also use it to detect changes between your own builds if its properties are sufficient for your use case.

    This feature has been added directly to output file objects since it's just a hash of the `contents` field, so it makes conceptual sense to store it in the same location. Another benefit of putting it there instead of including it as a part of the watch mode API is that it can be used without watch mode enabled. You can use it to compare the output of two independent builds that were done at different times.

    The hash algorithm (currently [XXH64](https://xxhash.com/)) is implementation-dependent and may be changed at any time in between esbuild versions. If you don't like esbuild's choice of hash algorithm then you are welcome to hash the contents yourself instead. As with any hash algorithm, note that while two different hashes mean that the contents are different, two equal hashes do not necessarily mean that the contents are equal. You may still want to compare the contents in addition to the hashes to detect with certainty when output files have been changed.

* Avoid generating duplicate prefixed declarations in CSS ([#3292](https://github.com/evanw/esbuild/issues/3292))

    There was a request for esbuild's CSS prefixer to avoid generating a prefixed declaration if a declaration by that name is already present in the same rule block. So with this release, esbuild will now avoid doing this:

    ```css
    /* Original code */
    body {
      backdrop-filter: blur(30px);
      -webkit-backdrop-filter: blur(45px);
    }

    /* Old output (with --target=safari12) */
    body {
      -webkit-backdrop-filter: blur(30px);
      backdrop-filter: blur(30px);
      -webkit-backdrop-filter: blur(45px);
    }

    /* New output (with --target=safari12) */
    body {
      backdrop-filter: blur(30px);
      -webkit-backdrop-filter: blur(45px);
    }
    ```

    This can result in a visual difference in certain cases (for example if the browser understands `blur(30px)` but not `blur(45px)`, it will be able to fall back to `blur(30px)`). But this change means esbuild now matches the behavior of [Autoprefixer](https://autoprefixer.github.io/) which is probably a good representation of how people expect this feature to work.

## 0.18.18

* Fix asset references with the `--line-limit` flag ([#3286](https://github.com/evanw/esbuild/issues/3286))

    The recently-released `--line-limit` flag tells esbuild to terminate long lines after they pass this length limit. This includes automatically wrapping long strings across multiple lines using escaped newline syntax. However, using this could cause esbuild to generate incorrect code for references from generated output files to assets in the bundle (i.e. files loaded with the `file` or `copy` loaders). This is because esbuild implements asset references internally using find-and-replace with a randomly-generated string, but the find operation fails if the string is split by an escaped newline due to line wrapping. This release fixes the problem by not wrapping these strings. This issue affected asset references in both JS and CSS files.

* Support local names in CSS for `@keyframe`, `@counter-style`, and `@container` ([#20](https://github.com/evanw/esbuild/issues/20))

    This release extends support for local names in CSS files loaded with the `local-css` loader to cover the `@keyframe`, `@counter-style`, and `@container` rules (and also `animation`, `list-style`, and `container` declarations). Here's an example:

    ```css
    @keyframes pulse {
      from, to { opacity: 1 }
      50% { opacity: 0.5 }
    }
    @counter-style moon {
      system: cyclic;
      symbols: 🌕 🌖 🌗 🌘 🌑 🌒 🌓 🌔;
    }
    @container squish {
      li { float: left }
    }
    ul {
      animation: 2s ease-in-out infinite pulse;
      list-style: inside moon;
      container: squish / size;
    }
    ```

    With the `local-css` loader enabled, that CSS will be turned into something like this (with the local name mapping exposed to JS):

    ```css
    @keyframes stdin_pulse {
      from, to {
        opacity: 1;
      }
      50% {
        opacity: 0.5;
      }
    }
    @counter-style stdin_moon {
      system: cyclic;
      symbols: 🌕 🌖 🌗 🌘 🌑 🌒 🌓 🌔;
    }
    @container stdin_squish {
      li {
        float: left;
      }
    }
    ul {
      animation: 2s ease-in-out infinite stdin_pulse;
      list-style: inside stdin_moon;
      container: stdin_squish / size;
    }
    ```

    If you want to use a global name within a file loaded with the `local-css` loader, you can use a `:global` selector to do that:

    ```css
    div {
      /* All symbols are global inside this scope (i.e.
       * "pulse", "moon", and "squish" are global below) */
      :global {
        animation: 2s ease-in-out infinite pulse;
        list-style: inside moon;
        container: squish / size;
      }
    }
    ```

    If you want to use `@keyframes`, `@counter-style`, or `@container` with a global name, make sure it's in a file that uses the `css` or `global-css` loader instead of the `local-css` loader. For example, you can configure `--loader:.module.css=local-css` so that the `local-css` loader only applies to `*.module.css` files.

* Support strings as keyframe animation names in CSS ([#2555](https://github.com/evanw/esbuild/issues/2555))

    With this release, esbuild will now parse animation names that are specified as strings and will convert them to identifiers. The CSS specification allows animation names to be specified using either identifiers or strings but Chrome only understands identifiers, so esbuild will now always convert string names to identifier names for Chrome compatibility:

    ```css
    /* Original code */
    @keyframes "hide menu" {
      from { opacity: 1 }
      to { opacity: 0 }
    }
    menu.hide {
      animation: 0.5s ease-in-out "hide menu";
    }

    /* Old output */
    @keyframes "hide menu" { from { opacity: 1 } to { opacity: 0 } }
    menu.hide {
      animation: 0.5s ease-in-out "hide menu";
    }

    /* New output */
    @keyframes hide\ menu {
      from {
        opacity: 1;
      }
      to {
        opacity: 0;
      }
    }
    menu.hide {
      animation: 0.5s ease-in-out hide\ menu;
    }
    ```

## 0.18.17

* Support `An+B` syntax and `:nth-*()` pseudo-classes in CSS

    This adds support for the `:nth-child()`, `:nth-last-child()`, `:nth-of-type()`, and `:nth-last-of-type()` pseudo-classes to esbuild, which has the following consequences:

    * The [`An+B` syntax](https://drafts.csswg.org/css-syntax-3/#anb-microsyntax) is now parsed, so parse errors are now reported
    * `An+B` values inside these pseudo-classes are now pretty-printed (e.g. a leading `+` will be stripped because it's not in the AST)
    * When minification is enabled, `An+B` values are reduced to equivalent but shorter forms (e.g. `2n+0` => `2n`, `2n+1` => `odd`)
    * Local CSS names in an `of` clause are now detected (e.g. in `:nth-child(2n of :local(.foo))` the name `foo` is now renamed)

    ```css
    /* Original code */
    .foo:nth-child(+2n+1 of :local(.bar)) {
      color: red;
    }

    /* Old output (with --loader=local-css) */
    .stdin_foo:nth-child(+2n + 1 of :local(.bar)) {
      color: red;
    }

    /* New output (with --loader=local-css) */
    .stdin_foo:nth-child(2n+1 of .stdin_bar) {
      color: red;
    }
    ```

* Adjust CSS nesting parser for IE7 hacks ([#3272](https://github.com/evanw/esbuild/issues/3272))

    This fixes a regression with esbuild's treatment of IE7 hacks in CSS. CSS nesting allows selectors to be used where declarations are expected. There's an IE7 hack where prefixing a declaration with a `*` causes that declaration to only be applied in IE7 due to a bug in IE7's CSS parser. However, it's valid for nested CSS selectors to start with `*`. So esbuild was incorrectly parsing these declarations and anything following it up until the next `{` as a selector for a nested CSS rule. This release changes esbuild's parser to terminate the parsing of selectors for nested CSS rules when a `;` is encountered to fix this edge case:

    ```css
    /* Original code */
    .item {
      *width: 100%;
      height: 1px;
    }

    /* Old output */
    .item {
      *width: 100%; height: 1px; {
      }
    }

    /* New output */
    .item {
      *width: 100%;
      height: 1px;
    }
    ```

    Note that the syntax for CSS nesting is [about to change again](https://github.com/w3c/csswg-drafts/issues/7961), so esbuild's CSS parser may still not be completely accurate with how browsers do and/or will interpret CSS nesting syntax. Expect additional updates to esbuild's CSS parser in the future to deal with upcoming CSS specification changes.

* Adjust esbuild's warning about undefined imports for TypeScript `import` equals declarations ([#3271](https://github.com/evanw/esbuild/issues/3271))

    In JavaScript, accessing a missing property on an import namespace object is supposed to result in a value of `undefined` at run-time instead of an error at compile-time. This is something that esbuild warns you about by default because doing this can indicate a bug with your code. For example:

    ```js
    // app.js
    import * as styles from './styles'
    console.log(styles.buton)
    ```

    ```js
    // styles.js
    export let button = {}
    ```

    If you bundle `app.js` with esbuild you will get this:

    ```
    ▲ [WARNING] Import "buton" will always be undefined because there is no matching export in "styles.js" [import-is-undefined]

        app.js:2:19:
          2 │ console.log(styles.buton)
            │                    ~~~~~
            ╵                    button

      Did you mean to import "button" instead?

        styles.js:1:11:
          1 │ export let button = {}
            ╵            ~~~~~~
    ```

    However, there is TypeScript-only syntax for `import` equals declarations that can represent either a type import (which esbuild should ignore) or a value import (which esbuild should respect). Since esbuild doesn't have a type system, it tries to only respect `import` equals declarations that are actually used as values. Previously esbuild always generated this warning for unused imports referenced within `import` equals declarations even when the reference could be a type instead of a value. Starting with this release, esbuild will now only warn in this case if the import is actually used. Here is an example of some code that no longer causes an incorrect warning:

    ```ts
    // app.ts
    import * as styles from './styles'
    import ButtonType = styles.Button
    ```

    ```ts
    // styles.ts
    export interface Button {}
    ```

## 0.18.16

* Fix a regression with whitespace inside `:is()` ([#3265](https://github.com/evanw/esbuild/issues/3265))

    The change to parse the contents of `:is()` in version 0.18.14 introduced a regression that incorrectly flagged the contents as a syntax error if the contents started with a whitespace token (for example `div:is( .foo ) {}`). This regression has been fixed.

## 0.18.15

* Add the `--serve-fallback=` option ([#2904](https://github.com/evanw/esbuild/issues/2904))

    The web server built into esbuild serves the latest in-memory results of the configured build. If the requested path doesn't match any in-memory build result, esbuild also provides the `--servedir=` option to tell esbuild to serve the requested path from that directory instead. And if the requested path doesn't match either of those things, esbuild will either automatically generate a directory listing (for directories) or return a 404 error.

    Starting with this release, that last step can now be replaced with telling esbuild to serve a specific HTML file using the `--serve-fallback=` option. This can be used to provide a "not found" page for missing URLs. It can also be used to implement a [single-page app](https://en.wikipedia.org/wiki/Single-page_application) that mutates the current URL and therefore requires the single app entry point to be served when the page is loaded regardless of whatever the current URL is.

* Use the `tsconfig` field in `package.json` during `extends` resolution ([#3247](https://github.com/evanw/esbuild/issues/3247))

     This release adds a feature from [TypeScript 3.2](https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-2.html#tsconfigjson-inheritance-via-nodejs-packages) where if a `tsconfig.json` file specifies a package name in the `extends` field and that package's `package.json` file has a `tsconfig` field, the contents of that field are used in the search for the base `tsconfig.json` file.

* Implement CSS nesting without `:is()` when possible ([#1945](https://github.com/evanw/esbuild/issues/1945))

    Previously esbuild would always produce a warning when transforming nested CSS for a browser that doesn't support the `:is()` pseudo-class. This was because the nesting transform needs to generate an `:is()` in some complex cases which means the transformed CSS would then not work in that browser. However, the CSS nesting transform can often be done without generating an `:is()`. So with this release, esbuild will no longer warn when targeting browsers that don't support `:is()` in the cases where an `:is()` isn't needed to represent the nested CSS.

    In addition, esbuild's nested CSS transform has been updated to avoid generating an `:is()` in cases where an `:is()` is preferable but there's a longer alternative that is also equivalent. This update means esbuild can now generate a combinatorial explosion of CSS for complex CSS nesting syntax when targeting browsers that don't support `:is()`. This combinatorial explosion is necessary to accurately represent the original semantics. For example:

    ```css
    /* Original code */
    .first,
    .second,
    .third {
      & > & {
        color: red;
      }
    }

    /* Old output (with --target=chrome80) */
    :is(.first, .second, .third) > :is(.first, .second, .third) {
      color: red;
    }

    /* New output (with --target=chrome80) */
    .first > .first,
    .first > .second,
    .first > .third,
    .second > .first,
    .second > .second,
    .second > .third,
    .third > .first,
    .third > .second,
    .third > .third {
      color: red;
    }
    ```

    This change means you can now use CSS nesting with esbuild when targeting an older browser that doesn't support `:is()`. You'll now only get a warning from esbuild if you use complex CSS nesting syntax that esbuild can't represent in that older browser without using `:is()`. There are two such cases:

    ```css
    /* Case 1 */
    a b {
      .foo & {
        color: red;
      }
    }

    /* Case 2 */
    a {
      > b& {
        color: red;
      }
    }
    ```

    These two cases still need to use `:is()`, both for different reasons, and cannot be used when targeting an older browser that doesn't support `:is()`:

    ```css
    /* Case 1 */
    .foo :is(a b) {
      color: red;
    }

    /* Case 2 */
    a > a:is(b) {
      color: red;
    }
    ```

* Automatically lower `inset` in CSS for older browsers

    With this release, esbuild will now automatically expand the `inset` property to the `top`, `right`, `bottom`, and `left` properties when esbuild's `target` is set to a browser that doesn't support `inset`:

    ```css
    /* Original code */
    .app {
      position: absolute;
      inset: 10px 20px;
    }

    /* Old output (with --target=chrome80) */
    .app {
      position: absolute;
      inset: 10px 20px;
    }

    /* New output (with --target=chrome80) */
    .app {
      position: absolute;
      top: 10px;
      right: 20px;
      bottom: 10px;
      left: 20px;
    }
    ```

* Add support for the new [`@starting-style`](https://drafts.csswg.org/css-transitions-2/#defining-before-change-style-the-starting-style-rule) CSS rule ([#3249](https://github.com/evanw/esbuild/pull/3249))

    This at rule allow authors to start CSS transitions on first style update. That is, you can now make the transition take effect when the `display` property changes from `none` to `block`.

    ```css
    /* Original code */
    @starting-style {
      h1 {
        background-color: transparent;
      }
    }

    /* Output */
    @starting-style{h1{background-color:transparent}}
    ```

    This was contributed by [@yisibl](https://github.com/yisibl).

## 0.18.14

* Implement local CSS names ([#20](https://github.com/evanw/esbuild/issues/20))

    This release introduces two new loaders called `global-css` and `local-css` and two new pseudo-class selectors `:local()` and `:global()`. This is a partial implementation of the popular [CSS modules](https://github.com/css-modules/css-modules) approach for avoiding unintentional name collisions in CSS. I'm not calling this feature "CSS modules" because although some people in the community call it that, other people in the community have started using "CSS modules" to refer to [something completely different](https://github.com/WICG/webcomponents/blob/60c9f682b63c622bfa0d8222ea6b1f3b659e007c/proposals/css-modules-v1-explainer.md) and now CSS modules is an overloaded term.

    Here's how this new local CSS name feature works with esbuild:

    * Identifiers that look like `.className` and `#idName` are global with the `global-css` loader and local with the `local-css` loader. Global identifiers are the same across all files (the way CSS normally works) but local identifiers are different between different files. If two separate CSS files use the same local identifier `.button`, esbuild will automatically rename one of them so that they don't collide. This is analogous to how esbuild automatically renames JS local variables with the same name in separate JS files to avoid name collisions.

    * It only makes sense to use local CSS names with esbuild when you are also using esbuild's bundler to bundle JS files that import CSS files. When you do that, esbuild will generate one export for each local name in the CSS file. The JS code can import these names and use them when constructing HTML DOM. For example:

        ```js
        // app.js
        import { outerShell } from './app.css'
        const div = document.createElement('div')
        div.className = outerShell
        document.body.appendChild(div)
        ```

        ```css
        /* app.css */
        .outerShell {
          position: absolute;
          inset: 0;
        }
        ```

        When you bundle this with `esbuild app.js --bundle --loader:.css=local-css --outdir=out` you'll now get this (notice how the local CSS name `outerShell` has been renamed):

        ```js
        // out/app.js
        (() => {
          // app.css
          var outerShell = "app_outerShell";

          // app.js
          var div = document.createElement("div");
          div.className = outerShell;
          document.body.appendChild(div);
        })();
        ```

        ```css
        /* out/app.css */
        .app_outerShell {
          position: absolute;
          inset: 0;
        }
        ```

        This feature only makes sense to use when bundling is enabled both because your code needs to `import` the renamed local names so that it can use them, and because esbuild needs to be able to process all CSS files containing local names in a single bundling operation so that it can successfully rename conflicting local names to avoid collisions.

    * If you are in a global CSS file (with the `global-css` loader) you can create a local name using `:local()`, and if you are in a local CSS file (with the `local-css` loader) you can create a global name with `:global()`. So the choice of the `global-css` loader vs. the `local-css` loader just sets the default behavior for identifiers, but you can override it on a case-by-case basis as necessary. For example:

        ```css
        :local(.button) {
          color: red;
        }
        :global(.button) {
          color: blue;
        }
        ```

        Processing this CSS file with esbuild with either the `global-css` or `local-css` loader will result in something like this:

        ```css
        .stdin_button {
          color: red;
        }
        .button {
          color: blue;
        }
        ```

    * The names that esbuild generates for local CSS names are an implementation detail and are not intended to be hard-coded anywhere. The only way you should be referencing the local CSS names in your JS or HTML is with an `import` statement in JS that is bundled with esbuild, as demonstrated above. For example, when `--minify` is enabled esbuild will use a different name generation algorithm which generates names that are as short as possible (analogous to how esbuild minifies local identifiers in JS).

    * You can easily use both global CSS files and local CSS files simultaneously if you give them different file extensions. For example, you could pass `--loader:.css=global-css` and `--loader:.module.css=local-css` to esbuild so that `.css` files still use global names by default but `.module.css` files use local names by default.

    * Keep in mind that the `css` loader is different than the `global-css` loader. The `:local` and `:global` annotations are not enabled with the `css` loader and will be passed through unchanged. This allows you to have the option of using esbuild to process CSS containing while preserving these annotations. It also means that local CSS names are disabled by default for now (since the `css` loader is currently the default for CSS files). The `:local` and `:global` syntax may be enabled by default in a future release.

    Note that esbuild's implementation does not currently have feature parity with other implementations of modular CSS in similar tools. This is only a preliminary release with a partial implementation that includes some basic behavior to get the process started. Additional behavior may be added in future releases. In particular, this release does not implement:

    * The `composes` pragma
    * Tree shaking for unused local CSS
    * Local names for keyframe animations, grid lines, `@container`, `@counter-style`, etc.

    Issue [#20](https://github.com/evanw/esbuild/issues/20) (the issue for this feature) is esbuild's most-upvoted issue! While this release still leaves that issue open, it's an important first step in that direction.

* Parse `:is`, `:has`, `:not`, and `:where` in CSS

    With this release, esbuild will now parse the contents of these pseudo-class selectors as a selector list. This means you will now get syntax warnings within these selectors for invalid selector syntax. It also means that esbuild's CSS nesting transform behaves slightly differently than before because esbuild is now operating on an AST instead of a token stream. For example:

    ```css
    /* Original code */
    div {
      :where(.foo&) {
        color: red;
      }
    }

    /* Old output (with --target=chrome90) */
    :where(.foo:is(div)) {
      color: red;
    }

    /* New output (with --target=chrome90) */
    :where(div.foo) {
      color: red;
    }
    ```

## 0.18.13

* Add the `--drop-labels=` option ([#2398](https://github.com/evanw/esbuild/issues/2398))

    If you want to conditionally disable some development-only code and have it not be present in the final production bundle, right now the most straightforward way of doing this is to use the `--define:` flag along with a specially-named global variable. For example, consider the following code:

    ```js
    function main() {
      DEV && doAnExpensiveCheck()
    }
    ```

    You can build this for development and production like this:

    * Development: `esbuild --define:DEV=true`
    * Production: `esbuild --define:DEV=false`

    One drawback of this approach is that the resulting code crashes if you don't provide a value for `DEV` with `--define:`. In practice this isn't that big of a problem, and there are also various ways to work around this.

    However, another approach that avoids this drawback is to use JavaScript label statements instead. That's what the `--drop-labels=` flag implements. For example, consider the following code:

    ```js
    function main() {
      DEV: doAnExpensiveCheck()
    }
    ```

    With this release, you can now build this for development and production like this:

    * Development: `esbuild`
    * Production: `esbuild --drop-labels=DEV`

    This means that code containing optional development-only checks can now be written such that it's safe to run without any additional configuration. The `--drop-labels=` flag takes comma-separated list of multiple label names to drop.

* Avoid causing `unhandledRejection` during shutdown ([#3219](https://github.com/evanw/esbuild/issues/3219))

    All pending esbuild JavaScript API calls are supposed to fail if esbuild's underlying child process is unexpectedly terminated. This can happen if `SIGINT` is sent to the parent `node` process with Ctrl+C, for example. Previously doing this could also cause an unhandled promise rejection when esbuild attempted to communicate this failure to its own child process that no longer exists. This release now swallows this communication failure, which should prevent this internal unhandled promise rejection. This change means that you can now use esbuild's JavaScript API with a custom `SIGINT` handler that extends the lifetime of the `node` process without esbuild's internals causing an early exit due to an unhandled promise rejection.

* Update browser compatibility table scripts

    The scripts that esbuild uses to compile its internal browser compatibility table have been overhauled. Briefly:

    * Converted from JavaScript to TypeScript
    * Fixed some bugs that resulted in small changes to the table
    * Added [`caniuse-lite`](https://www.npmjs.com/package/caniuse-lite) and [`@mdn/browser-compat-data`](https://www.npmjs.com/package/@mdn/browser-compat-data) as new data sources (replacing manually-copied information)

    This change means it's now much easier to keep esbuild's internal compatibility tables up to date. You can review the table changes here if you need to debug something about this change:

    * [JS table changes](https://github.com/evanw/esbuild/compare/d259b8fac717ee347c19bd8299f2c26d7c87481a...af1d35c372f78c14f364b63e819fd69548508f55#diff-1649eb68992c79753469f02c097de309adaf7231b45cc816c50bf751af400eb4)
    * [CSS table changes](https://github.com/evanw/esbuild/commit/95feb2e09877597cb929469ce43811bdf11f50c1#diff-4e1c4f269e02c5ea31cbd5138d66751e32cf0e240524ee8a966ac756f0e3c3cd)

## 0.18.12

* Fix a panic with `const enum` inside parentheses ([#3205](https://github.com/evanw/esbuild/issues/3205))

    This release fixes an edge case where esbuild could potentially panic if a TypeScript `const enum` statement was used inside of a parenthesized expression and was followed by certain other scope-related statements. Here's a minimal example that triggers this edge case:

    ```ts
    (() => {
      const enum E { a };
      () => E.a
    })
    ```

* Allow a newline in the middle of TypeScript `export type` statement ([#3225](https://github.com/evanw/esbuild/issues/3225))

    Previously esbuild incorrectly rejected the following valid TypeScript code:

    ```ts
    export type
    { T };

    export type
    * as foo from 'bar';
    ```

    Code that uses a newline after `export type` is now allowed starting with this release.

* Fix cross-module inlining of string enums ([#3210](https://github.com/evanw/esbuild/issues/3210))

    A refactoring typo in version 0.18.9 accidentally introduced a regression with cross-module inlining of string enums when combined with computed property accesses. This regression has been fixed.

* Rewrite `.js` to `.ts` inside packages with `exports` ([#3201](https://github.com/evanw/esbuild/issues/3201))

    Packages with the `exports` field are supposed to disable node's path resolution behavior that allows you to import a file with a different extension than the one in the source code (for example, importing `foo/bar` to get `foo/bar.js`). And TypeScript has behavior where you can import a non-existent `.js` file and you will get the `.ts` file instead. Previously the presence of the `exports` field caused esbuild to disable all extension manipulation stuff which included both node's implicit file extension searching and TypeScript's file extension swapping. However, TypeScript appears to always apply file extension swapping even in this case. So with this release, esbuild will now rewrite `.js` to `.ts` even inside packages with `exports`.

* Fix a redirect edge case in esbuild's development server ([#3208](https://github.com/evanw/esbuild/issues/3208))

    The development server canonicalizes directory URLs by adding a trailing slash. For example, visiting `/about` redirects to `/about/` if `/about/index.html` would be served. However, if the requested path begins with two slashes, then the redirect incorrectly turned into a protocol-relative URL. For example, visiting `//about` redirected to `//about/` which the browser turns into `http://about/`. This release fixes the bug by canonicalizing the URL path when doing this redirect.

## 0.18.11

* Fix a TypeScript code generation edge case ([#3199](https://github.com/evanw/esbuild/issues/3199))

    This release fixes a regression in version 0.18.4 where using a TypeScript `namespace` that exports a `class` declaration combined with `--keep-names` and a `--target` of `es2021` or earlier could cause esbuild to export the class from the namespace using an incorrect name (notice the assignment to `X2._Y` vs. `X2.Y`):

    ```ts
    // Original code

    // Old output (with --keep-names --target=es2021)
    var X;
    ((X2) => {
      const _Y = class _Y {
      };
      __name(_Y, "Y");
      let Y = _Y;
      X2._Y = _Y;
    })(X || (X = {}));

    // New output (with --keep-names --target=es2021)
    var X;
    ((X2) => {
      const _Y = class _Y {
      };
      __name(_Y, "Y");
      let Y = _Y;
      X2.Y = _Y;
    })(X || (X = {}));
    ```

## 0.18.10

* Fix a tree-shaking bug that removed side effects ([#3195](https://github.com/evanw/esbuild/issues/3195))

    This fixes a regression in version 0.18.4 where combining `--minify-syntax` with `--keep-names` could cause expressions with side effects after a function declaration to be considered side-effect free for tree shaking purposes. The reason was because `--keep-names` generates an expression statement containing a call to a helper function after the function declaration with a special flag that makes the function call able to be tree shaken, and then `--minify-syntax` could potentially merge that expression statement with following expressions without clearing the flag. This release fixes the bug by clearing the flag when merging expression statements together.

* Fix an incorrect warning about CSS nesting ([#3197](https://github.com/evanw/esbuild/issues/3197))

    A warning is currently generated when transforming nested CSS to a browser that doesn't support `:is()` because transformed nested CSS may need to use that feature to represent nesting. This was previously always triggered when an at-rule was encountered in a declaration context. Typically the only case you would encounter this is when using CSS nesting within a selector rule. However, there is a case where that's not true: when using a margin at-rule such as `@top-left` within `@page`. This release avoids incorrectly generating a warning in this case by checking that the at-rule is within a selector rule before generating a warning.

## 0.18.9

* Fix `await using` declarations inside `async` generator functions

    I forgot about the new `await using` declarations when implementing lowering for `async` generator functions in the previous release. This change fixes the transformation of `await using` declarations when they are inside lowered `async` generator functions:

    ```js
    // Original code
    async function* foo() {
      await using x = await y
    }

    // Old output (with --supported:async-generator=false)
    function foo() {
      return __asyncGenerator(this, null, function* () {
        await using x = yield new __await(y);
      });
    }

    // New output (with --supported:async-generator=false)
    function foo() {
      return __asyncGenerator(this, null, function* () {
        var _stack = [];
        try {
          const x = __using(_stack, yield new __await(y), true);
        } catch (_) {
          var _error = _, _hasError = true;
        } finally {
          var _promise = __callDispose(_stack, _error, _hasError);
          _promise && (yield new __await(_promise));
        }
      });
    }
    ```

* Insert some prefixed CSS properties when appropriate ([#3122](https://github.com/evanw/esbuild/issues/3122))

    With this release, esbuild will now insert prefixed CSS properties in certain cases when the `target` setting includes browsers that require a certain prefix. This is currently done for the following properties:

    * `appearance: *;` => `-webkit-appearance: *; -moz-appearance: *;`
    * `backdrop-filter: *;` => `-webkit-backdrop-filter: *;`
    * `background-clip: text` => `-webkit-background-clip: text;`
    * `box-decoration-break: *;` => `-webkit-box-decoration-break: *;`
    * `clip-path: *;` => `-webkit-clip-path: *;`
    * `font-kerning: *;` => `-webkit-font-kerning: *;`
    * `hyphens: *;` => `-webkit-hyphens: *;`
    * `initial-letter: *;` => `-webkit-initial-letter: *;`
    * `mask-image: *;` => `-webkit-mask-image: *;`
    * `mask-origin: *;` => `-webkit-mask-origin: *;`
    * `mask-position: *;` => `-webkit-mask-position: *;`
    * `mask-repeat: *;` => `-webkit-mask-repeat: *;`
    * `mask-size: *;` => `-webkit-mask-size: *;`
    * `position: sticky;` => `position: -webkit-sticky;`
    * `print-color-adjust: *;` => `-webkit-print-color-adjust: *;`
    * `tab-size: *;` => `-moz-tab-size: *; -o-tab-size: *;`
    * `text-decoration-color: *;` => `-webkit-text-decoration-color: *; -moz-text-decoration-color: *;`
    * `text-decoration-line: *;` => `-webkit-text-decoration-line: *; -moz-text-decoration-line: *;`
    * `text-decoration-skip: *;` => `-webkit-text-decoration-skip: *;`
    * `text-emphasis-color: *;` => `-webkit-text-emphasis-color: *;`
    * `text-emphasis-position: *;` => `-webkit-text-emphasis-position: *;`
    * `text-emphasis-style: *;` => `-webkit-text-emphasis-style: *;`
    * `text-orientation: *;` => `-webkit-text-orientation: *;`
    * `text-size-adjust: *;` => `-webkit-text-size-adjust: *; -ms-text-size-adjust: *;`
    * `user-select: *;` => `-webkit-user-select: *; -moz-user-select: *; -ms-user-select: *;`

    Here is an example:

    ```css
    /* Original code */
    div {
      mask-image: url(x.png);
    }

    /* Old output (with --target=chrome99) */
    div {
      mask-image: url(x.png);
    }

    /* New output (with --target=chrome99) */
    div {
      -webkit-mask-image: url(x.png);
      mask-image: url(x.png);
    }
    ```

    Browser compatibility data was sourced from the tables on https://caniuse.com. Support for more CSS properties can be added in the future as appropriate.

* Fix an obscure identifier minification bug ([#2809](https://github.com/evanw/esbuild/issues/2809))

    Function declarations in nested scopes behave differently depending on whether or not `"use strict"` is present. To avoid generating code that behaves differently depending on whether strict mode is enabled or not, esbuild transforms nested function declarations into variable declarations. However, there was a bug where the generated variable name was not being recorded as declared internally, which meant that it wasn't being renamed correctly by the minifier and could cause a name collision. This bug has been fixed:

    ```js
    // Original code
    const n = ''
    for (let i of [0,1]) {
      function f () {}
    }

    // Old output (with --minify-identifiers --format=esm)
    const f = "";
    for (let o of [0, 1]) {
      let n = function() {
      };
      var f = n;
    }

    // New output (with --minify-identifiers --format=esm)
    const f = "";
    for (let o of [0, 1]) {
      let n = function() {
      };
      var t = n;
    }
    ```

* Fix a bug in esbuild's compatibility table script ([#3179](https://github.com/evanw/esbuild/pull/3179))

    Setting esbuild's `target` to a specific JavaScript engine tells esbuild to use the JavaScript syntax feature compatibility data from https://kangax.github.io/compat-table/es6/ for that engine to determine which syntax features to allow. However, esbuild's script that builds this internal compatibility table had a bug that incorrectly ignores tests for engines that still have outstanding implementation bugs which were never fixed. This change fixes this bug with the script.

    The only case where this changed the information in esbuild's internal compatibility table is that the `hermes` target is marked as no longer supporting destructuring. This is because there is a failing destructuring-related test for Hermes on https://kangax.github.io/compat-table/es6/. If you want to use destructuring with Hermes anyway, you can pass `--supported:destructuring=true` to esbuild to override the `hermes` target and force esbuild to accept this syntax.

    This fix was contributed by [@ArrayZoneYour](https://github.com/ArrayZoneYour).

## 0.18.8

* Implement transforming `async` generator functions ([#2780](https://github.com/evanw/esbuild/issues/2780))

    With this release, esbuild will now transform `async` generator functions into normal generator functions when the configured target environment doesn't support them. These functions behave similar to normal generator functions except that they use the `Symbol.asyncIterator` interface instead of the `Symbol.iterator` interface and the iteration methods return promises. Here's an example (helper functions are omitted):

    ```js
    // Original code
    async function* foo() {
      yield Promise.resolve(1)
      await new Promise(r => setTimeout(r, 100))
      yield *[Promise.resolve(2)]
    }
    async function bar() {
      for await (const x of foo()) {
        console.log(x)
      }
    }
    bar()

    // New output (with --target=es6)
    function foo() {
      return __asyncGenerator(this, null, function* () {
        yield Promise.resolve(1);
        yield new __await(new Promise((r) => setTimeout(r, 100)));
        yield* __yieldStar([Promise.resolve(2)]);
      });
    }
    function bar() {
      return __async(this, null, function* () {
        try {
          for (var iter = __forAwait(foo()), more, temp, error; more = !(temp = yield iter.next()).done; more = false) {
            const x = temp.value;
            console.log(x);
          }
        } catch (temp) {
          error = [temp];
        } finally {
          try {
            more && (temp = iter.return) && (yield temp.call(iter));
          } finally {
            if (error)
              throw error[0];
          }
        }
      });
    }
    bar();
    ```

    This is an older feature that was added to JavaScript in ES2018 but I didn't implement the transformation then because it's a rarely-used feature. Note that esbuild already added support for transforming `for await` loops (the other part of the [asynchronous iteration proposal](https://github.com/tc39/proposal-async-iteration)) a year ago, so support for asynchronous iteration should now be complete.

    I have never used this feature myself and code that uses this feature is hard to come by, so this transformation has not yet been tested on real-world code. If you do write code that uses this feature, please let me know if esbuild's `async` generator transformation doesn't work with your code.

## 0.18.7

* Add support for `using` declarations in TypeScript 5.2+ ([#3191](https://github.com/evanw/esbuild/issues/3191))

    TypeScript 5.2 (due to be released in August of 2023) will introduce `using` declarations, which will allow you to automatically dispose of the declared resources when leaving the current scope. You can read the [TypeScript PR for this feature](https://github.com/microsoft/TypeScript/pull/54505) for more information. This release of esbuild adds support for transforming this syntax to target environments without support for `using` declarations (which is currently all targets other than `esnext`). Here's an example (helper functions are omitted):

    ```js
    // Original code
    class Foo {
      [Symbol.dispose]() {
        console.log('cleanup')
      }
    }
    using foo = new Foo;
    foo.bar();

    // New output (with --target=es6)
    var _stack = [];
    try {
      var Foo = class {
        [Symbol.dispose]() {
          console.log("cleanup");
        }
      };
      var foo = __using(_stack, new Foo());
      foo.bar();
    } catch (_) {
      var _error = _, _hasError = true;
    } finally {
      __callDispose(_stack, _error, _hasError);
    }
    ```

    The injected helper functions ensure that the method named `Symbol.dispose` is called on `new Foo` when control exits the scope. Note that as with all new JavaScript APIs, you'll need to polyfill `Symbol.dispose` if it's not present before you use it. This is not something that esbuild does for you because esbuild only handles syntax, not APIs. Polyfilling it can be done with something like this:

    ```js
    Symbol.dispose ||= Symbol('Symbol.dispose')
    ```

    This feature also introduces `await using` declarations which are like `using` declarations but they call `await` on the disposal method (not on the initializer). Here's an example (helper functions are omitted):

    ```js
    // Original code
    class Foo {
      async [Symbol.asyncDispose]() {
        await new Promise(done => {
          setTimeout(done, 1000)
        })
        console.log('cleanup')
      }
    }
    await using foo = new Foo;
    foo.bar();

    // New output (with --target=es2022)
    var _stack = [];
    try {
      var Foo = class {
        async [Symbol.asyncDispose]() {
          await new Promise((done) => {
            setTimeout(done, 1e3);
          });
          console.log("cleanup");
        }
      };
      var foo = __using(_stack, new Foo(), true);
      foo.bar();
    } catch (_) {
      var _error = _, _hasError = true;
    } finally {
      var _promise = __callDispose(_stack, _error, _hasError);
      _promise && await _promise;
    }
    ```

    The injected helper functions ensure that the method named `Symbol.asyncDispose` is called on `new Foo` when control exits the scope, and that the returned promise is awaited. Similarly to `Symbol.dispose`, you'll also need to polyfill `Symbol.asyncDispose` before you use it.

* Add a `--line-limit=` flag to limit line length ([#3170](https://github.com/evanw/esbuild/issues/3170))

    Long lines are common in minified code. However, many tools and text editors can't handle long lines. This release introduces the `--line-limit=` flag to tell esbuild to wrap lines longer than the provided number of bytes. For example, `--line-limit=80` tells esbuild to insert a newline soon after a given line reaches 80 bytes in length. This setting applies to both JavaScript and CSS, and works even when minification is disabled. Note that turning this setting on will make your files bigger, as the extra newlines take up additional space in the file (even after gzip compression).

## 0.18.6

* Fix tree-shaking of classes with decorators ([#3164](https://github.com/evanw/esbuild/issues/3164))

    This release fixes a bug where esbuild incorrectly allowed tree-shaking on classes with decorators. Each decorator is a function call, so classes with decorators must never be tree-shaken. This bug was a regression that was unintentionally introduced in version 0.18.2 by the change that enabled tree-shaking of lowered private fields. Previously decorators were always lowered, and esbuild always considered the automatically-generated decorator code to be a side effect. But this is no longer the case now that esbuild analyzes side effects using the AST before lowering takes place. This bug was fixed by considering any decorator a side effect.

* Fix a minification bug involving function expressions ([#3125](https://github.com/evanw/esbuild/issues/3125))

    When minification is enabled, esbuild does limited inlining of `const` symbols at the top of a scope. This release fixes a bug where inlineable symbols were incorrectly removed assuming that they were inlined. They may not be inlined in cases where they were referenced by earlier constants in the body of a function expression. The declarations involved in these edge cases are now kept instead of being removed:

    ```js
    // Original code
    {
      const fn = () => foo
      const foo = 123
      console.log(fn)
    }

    // Old output (with --minify-syntax)
    console.log((() => foo)());

    // New output (with --minify-syntax)
    {
      const fn = () => foo, foo = 123;
      console.log(fn);
    }
    ```

## 0.18.5

* Implement auto accessors ([#3009](https://github.com/evanw/esbuild/issues/3009))

    This release implements the new auto-accessor syntax from the upcoming [JavaScript decorators proposal](https://github.com/tc39/proposal-decorators). The auto-accessor syntax looks like this:

    ```js
    class Foo {
      accessor foo;
      static accessor bar;
    }
    new Foo().foo = Foo.bar;
    ```

    This syntax is not yet a part of JavaScript but it was [added to TypeScript in version 4.9](https://devblogs.microsoft.com/typescript/announcing-typescript-4-9/#auto-accessors-in-classes). More information about this feature can be found in [microsoft/TypeScript#49705](https://github.com/microsoft/TypeScript/pull/49705). Auto-accessors will be transformed if the target is set to something other than `esnext`:

    ```js
    // Output (with --target=esnext)
    class Foo {
      accessor foo;
      static accessor bar;
    }
    new Foo().foo = Foo.bar;

    // Output (with --target=es2022)
    class Foo {
      #foo;
      get foo() {
        return this.#foo;
      }
      set foo(_) {
        this.#foo = _;
      }
      static #bar;
      static get bar() {
        return this.#bar;
      }
      static set bar(_) {
        this.#bar = _;
      }
    }
    new Foo().foo = Foo.bar;

    // Output (with --target=es2021)
    var _foo, _bar;
    class Foo {
      constructor() {
        __privateAdd(this, _foo, void 0);
      }
      get foo() {
        return __privateGet(this, _foo);
      }
      set foo(_) {
        __privateSet(this, _foo, _);
      }
      static get bar() {
        return __privateGet(this, _bar);
      }
      static set bar(_) {
        __privateSet(this, _bar, _);
      }
    }
    _foo = new WeakMap();
    _bar = new WeakMap();
    __privateAdd(Foo, _bar, void 0);
    new Foo().foo = Foo.bar;
    ```

    You can also now use auto-accessors with esbuild's TypeScript experimental decorator transformation, which should behave the same as decorating the underlying getter/setter pair.

    **Please keep in mind that this syntax is not yet part of JavaScript.** This release enables auto-accessors in `.js` files with the expectation that it will be a part of JavaScript soon. However, esbuild may change or remove this feature in the future if JavaScript ends up changing or removing this feature. Use this feature with caution for now.

* Pass through JavaScript decorators ([#104](https://github.com/evanw/esbuild/issues/104))

    In this release, esbuild now parses decorators from the upcoming [JavaScript decorators proposal](https://github.com/tc39/proposal-decorators) and passes them through to the output unmodified (as long as the language target is set to `esnext`). Transforming JavaScript decorators to environments that don't support them has not been implemented yet. The only decorator transform that esbuild currently implements is still the TypeScript experimental decorator transform, which only works in `.ts` files and which requires `"experimentalDecorators": true` in your `tsconfig.json` file.

* Static fields with assign semantics now use static blocks if possible

    Setting `useDefineForClassFields` to false in TypeScript requires rewriting class fields to assignment statements. Previously this was done by removing the field from the class body and adding an assignment statement after the class declaration. However, this also caused any private fields to also be lowered by necessity (in case a field initializer uses a private symbol, either directly or indirectly). This release changes this transform to use an inline static block if it's supported, which avoids needing to lower private fields in this scenario:

    ```js
    // Original code
    class Test {
      static #foo = 123
      static bar = this.#foo
    }

    // Old output (with useDefineForClassFields=false)
    var _foo;
    const _Test = class _Test {
    };
    _foo = new WeakMap();
    __privateAdd(_Test, _foo, 123);
    _Test.bar = __privateGet(_Test, _foo);
    let Test = _Test;

    // New output (with useDefineForClassFields=false)
    class Test {
      static #foo = 123;
      static {
        this.bar = this.#foo;
      }
    }
    ```

* Fix TypeScript experimental decorators combined with `--mangle-props` ([#3177](https://github.com/evanw/esbuild/issues/3177))

    Previously using TypeScript experimental decorators combined with the `--mangle-props` setting could result in a crash, as the experimental decorator transform was not expecting a mangled property as a class member. This release fixes the crash so you can now combine both of these features together safely.

## 0.18.4

* Bundling no longer unnecessarily transforms class syntax ([#1360](https://github.com/evanw/esbuild/issues/1360), [#1328](https://github.com/evanw/esbuild/issues/1328), [#1524](https://github.com/evanw/esbuild/issues/1524), [#2416](https://github.com/evanw/esbuild/issues/2416))

    When bundling, esbuild automatically converts top-level class statements to class expressions. Previously this conversion had the unfortunate side-effect of also transforming certain other class-related syntax features to avoid correctness issues when the references to the class name within the class body. This conversion has been reworked to avoid doing this:

    ```js
    // Original code
    export class Foo {
      static foo = () => Foo
    }

    // Old output (with --bundle)
    var _Foo = class {
    };
    var Foo = _Foo;
    __publicField(Foo, "foo", () => _Foo);

    // New output (with --bundle)
    var Foo = class _Foo {
      static foo = () => _Foo;
    };
    ```

    This conversion process is very complicated and has many edge cases (including interactions with static fields, static blocks, private class properties, and TypeScript experimental decorators). It should already be pretty robust but a change like this may introduce new unintentional behavior. Please report any issues with this upgrade on the esbuild bug tracker.

    You may be wondering why esbuild needs to do this at all. One reason to do this is that esbuild's bundler sometimes needs to lazily-evaluate a module. For example, a module may end up being both the target of a dynamic `import()` call and a static `import` statement. Lazy module evaluation is done by wrapping the top-level module code in a closure. To avoid a performance hit for static `import` statements, esbuild stores top-level exported symbols outside of the closure and references them directly instead of indirectly.

    Another reason to do this is that multiple JavaScript VMs have had and continue to have performance issues with TDZ (i.e. "temporal dead zone") checks. These checks validate that a let, or const, or class symbol isn't used before it's initialized. Here are two issues with well-known VMs:

    * V8: https://bugs.chromium.org/p/v8/issues/detail?id=13723 (10% slowdown)
    * JavaScriptCore: https://bugs.webkit.org/show_bug.cgi?id=199866 (1,000% slowdown!)

    JavaScriptCore had a severe performance issue as their TDZ implementation had time complexity that was quadratic in the number of variables needing TDZ checks in the same scope (with the top-level scope typically being the worst offender). V8 has ongoing issues with TDZ checks being present throughout the code their JIT generates even when they have already been checked earlier in the same function or when the function in question has already been run (so the checks have already happened).

    Due to esbuild's parallel architecture, esbuild both a) needs to convert class statements into class expressions during parsing and b) doesn't yet know whether this module will need to be lazily-evaluated or not in the parser. So esbuild always does this conversion during bundling in case it's needed for correctness (and also to avoid potentially catastrophic performance issues due to bundling creating a large scope with many TDZ variables).

* Enforce TDZ errors in computed class property keys ([#2045](https://github.com/evanw/esbuild/issues/2045))

    JavaScript allows class property keys to be generated at run-time using code, like this:

    ```js
    class Foo {
      static foo = 'foo'
      static [Foo.foo + '2'] = 2
    }
    ```

    Previously esbuild treated references to the containing class name within computed property keys as a reference to the partially-initialized class object. That meant code that attempted to reference properties of the class object (such as the code above) would get back `undefined` instead of throwing an error.

    This release rewrites references to the containing class name within computed property keys into code that always throws an error at run-time, which is how this JavaScript code is supposed to work. Code that does this will now also generate a warning. You should never write code like this, but it now should be more obvious when incorrect code like this is written.

* Fix an issue with experimental decorators and static fields ([#2629](https://github.com/evanw/esbuild/issues/2629))

    This release also fixes a bug regarding TypeScript experimental decorators and static class fields which reference the enclosing class name in their initializer. This affected top-level classes when bundling was enabled. Previously code that does this could crash because the class name wasn't initialized yet. This case should now be handled correctly:

    ```ts
    // Original code
    class Foo {
      @someDecorator
      static foo = 'foo'
      static bar = Foo.foo.length
    }

    // Old output
    const _Foo = class {
      static foo = "foo";
      static bar = _Foo.foo.length;
    };
    let Foo = _Foo;
    __decorateClass([
      someDecorator
    ], Foo, "foo", 2);

    // New output
    const _Foo = class _Foo {
      static foo = "foo";
      static bar = _Foo.foo.length;
    };
    __decorateClass([
      someDecorator
    ], _Foo, "foo", 2);
    let Foo = _Foo;
    ```

* Fix a minification regression with negative numeric properties ([#3169](https://github.com/evanw/esbuild/issues/3169))

    Version 0.18.0 introduced a regression where computed properties with negative numbers were incorrectly shortened into a non-computed property when minification was enabled. This regression has been fixed:

    ```js
    // Original code
    x = {
      [1]: 1,
      [-1]: -1,
      [NaN]: NaN,
      [Infinity]: Infinity,
      [-Infinity]: -Infinity,
    }

    // Old output (with --minify)
    x={1:1,-1:-1,NaN:NaN,1/0:1/0,-1/0:-1/0};

    // New output (with --minify)
    x={1:1,[-1]:-1,NaN:NaN,[1/0]:1/0,[-1/0]:-1/0};
    ```

## 0.18.3

* Fix a panic due to empty static class blocks ([#3161](https://github.com/evanw/esbuild/issues/3161))

    This release fixes a bug where an internal invariant that was introduced in the previous release was sometimes violated, which then caused a panic. It happened when bundling code containing an empty static class block with both minification and bundling enabled.

## 0.18.2

* Lower static blocks when static fields are lowered ([#2800](https://github.com/evanw/esbuild/issues/2800), [#2950](https://github.com/evanw/esbuild/issues/2950), [#3025](https://github.com/evanw/esbuild/issues/3025))

    This release fixes a bug where esbuild incorrectly did not lower static class blocks when static class fields needed to be lowered. For example, the following code should print `1 2 3` but previously printed `2 1 3` instead due to this bug:

    ```js
    // Original code
    class Foo {
      static x = console.log(1)
      static { console.log(2) }
      static y = console.log(3)
    }

    // Old output (with --supported:class-static-field=false)
    class Foo {
      static {
        console.log(2);
      }
    }
    __publicField(Foo, "x", console.log(1));
    __publicField(Foo, "y", console.log(3));

    // New output (with --supported:class-static-field=false)
    class Foo {
    }
    __publicField(Foo, "x", console.log(1));
    console.log(2);
    __publicField(Foo, "y", console.log(3));
    ```

* Use static blocks to implement `--keep-names` on classes ([#2389](https://github.com/evanw/esbuild/issues/2389))

    This change fixes a bug where the `name` property could previously be incorrect within a class static context when using `--keep-names`. The problem was that the `name` property was being initialized after static blocks were run instead of before. This has been fixed by moving the `name` property initializer into a static block at the top of the class body:

    ```js
    // Original code
    if (typeof Foo === 'undefined') {
      let Foo = class {
        static test = this.name
      }
      console.log(Foo.test)
    }

    // Old output (with --keep-names)
    if (typeof Foo === "undefined") {
      let Foo2 = /* @__PURE__ */ __name(class {
        static test = this.name;
      }, "Foo");
      console.log(Foo2.test);
    }

    // New output (with --keep-names)
    if (typeof Foo === "undefined") {
      let Foo2 = class {
        static {
          __name(this, "Foo");
        }
        static test = this.name;
      };
      console.log(Foo2.test);
    }
    ```

    This change was somewhat involved, especially regarding what esbuild considers to be side-effect free. Some unused classes that weren't removed by tree shaking in previous versions of esbuild may now be tree-shaken. One example is classes with static private fields that are transformed by esbuild into code that doesn't use JavaScript's private field syntax. Previously esbuild's tree shaking analysis ran on the class after syntax lowering, but with this release it will run on the class before syntax lowering, meaning it should no longer be confused by class mutations resulting from automatically-generated syntax lowering code.

## 0.18.1

* Fill in `null` entries in input source maps ([#3144](https://github.com/evanw/esbuild/issues/3144))

    If esbuild bundles input files with source maps and those source maps contain a `sourcesContent` array with `null` entries, esbuild previously copied those `null` entries over to the output source map. With this release, esbuild will now attempt to fill in those `null` entries by looking for a file on the file system with the corresponding name from the `sources` array. This matches esbuild's existing behavior that automatically generates the `sourcesContent` array from the file system if the entire `sourcesContent` array is missing.

* Support `/* @__KEY__ */` comments for mangling property names ([#2574](https://github.com/evanw/esbuild/issues/2574))

    Property mangling is an advanced feature that enables esbuild to minify certain property names, even though it's not possible to automatically determine that it's safe to do so. The safe property names are configured via regular expression such as `--mangle-props=_$` (mangle all properties ending in `_`).

    Sometimes it's desirable to also minify strings containing property names, even though it's not possible to automatically determine which strings are property names. This release makes it possible to do this by annotating those strings with `/* @__KEY__ */`. This is a convention that Terser added earlier this year, and which esbuild is now following too: https://github.com/terser/terser/pull/1365. Using it looks like this:

    ```js
    // Original code
    console.log(
      [obj.mangle_, obj.keep],
      [obj.get('mangle_'), obj.get('keep')],
      [obj.get(/* @__KEY__ */ 'mangle_'), obj.get(/* @__KEY__ */ 'keep')],
    )

    // Old output (with --mangle-props=_$)
    console.log(
      [obj.a, obj.keep],
      [obj.get("mangle_"), obj.get("keep")],
      [obj.get(/* @__KEY__ */ "mangle_"), obj.get(/* @__KEY__ */ "keep")]
    );

    // New output (with --mangle-props=_$)
    console.log(
      [obj.a, obj.keep],
      [obj.get("mangle_"), obj.get("keep")],
      [obj.get(/* @__KEY__ */ "a"), obj.get(/* @__KEY__ */ "keep")]
    );
    ```

* Support `/* @__NO_SIDE_EFFECTS__ */` comments for functions ([#3149](https://github.com/evanw/esbuild/issues/3149))

    Rollup has recently added support for `/* @__NO_SIDE_EFFECTS__ */` annotations before functions to indicate that calls to these functions can be removed if the result is unused (i.e. the calls can be assumed to have no side effects). This release adds basic support for these to esbuild as well, which means esbuild will now parse these comments in input files and preserve them in output files. This should help people that use esbuild in combination with Rollup.

    Note that this doesn't necessarily mean esbuild will treat these calls as having no side effects, as esbuild's parallel architecture currently isn't set up to enable this type of cross-file tree-shaking information (tree-shaking decisions regarding a function call are currently local to the file they appear in). If you want esbuild to consider a function call to have no side effects, make sure you continue to annotate the function call with `/* @__PURE__ */` (which is the previously-established convention for communicating this).

## 0.18.0

**This release deliberately contains backwards-incompatible changes.** To avoid automatically picking up releases like this, you should either be pinning the exact version of `esbuild` in your `package.json` file (recommended) or be using a version range syntax that only accepts patch upgrades such as `^0.17.0` or `~0.17.0`. See npm's documentation about [semver](https://docs.npmjs.com/cli/v6/using-npm/semver/) for more information.

The breaking changes in this release mainly focus on fixing some long-standing issues with esbuild's handling of `tsconfig.json` files. Here are all the changes in this release, in detail:

* Add a way to try esbuild online ([#797](https://github.com/evanw/esbuild/issues/797))

    There is now a way to try esbuild live on esbuild's website without installing it: https://esbuild.github.io/try/. In addition to being able to more easily evaluate esbuild, this should also make it more efficient to generate esbuild bug reports. For example, you can use it to compare the behavior of different versions of esbuild on the same input. The state of the page is stored in the URL for easy sharing. Many thanks to [@hyrious](https://github.com/hyrious) for creating https://hyrious.me/esbuild-repl/, which was the main inspiration for this addition to esbuild's website.

    Two forms of build options are supported: either CLI-style ([example](https://esbuild.github.io/try/#dAAwLjE3LjE5AC0tbG9hZGVyPXRzeCAtLW1pbmlmeSAtLXNvdXJjZW1hcABsZXQgZWw6IEpTWC5FbGVtZW50ID0gPGRpdiAvPg)) or JS-style ([example](https://esbuild.github.io/try/#dAAwLjE3LjE5AHsKICBsb2FkZXI6ICd0c3gnLAogIG1pbmlmeTogdHJ1ZSwKICBzb3VyY2VtYXA6IHRydWUsCn0AbGV0IGVsOiBKU1guRWxlbWVudCA9IDxkaXYgLz4)). Both are converted into a JS object that's passed to esbuild's WebAssembly API. The CLI-style argument parser is a custom one that simulates shell quoting rules, and the JS-style argument parser is also custom and parses a superset of JSON (basically JSON5 + regular expressions). So argument parsing is an approximate simulation of what happens for real but hopefully it should be close enough.

* Changes to esbuild's `tsconfig.json` support ([#3019](https://github.com/evanw/esbuild/issues/3019)):

    This release makes the following changes to esbuild's `tsconfig.json` support:

    * Using experimental decorators now requires `"experimentalDecorators": true` ([#104](https://github.com/evanw/esbuild/issues/104))

        Previously esbuild would always compile decorators in TypeScript code using TypeScript's experimental decorator transform. Now that standard JavaScript decorators are close to being finalized, esbuild will now require you to use `"experimentalDecorators": true` to do this. This new requirement makes it possible for esbuild to introduce a transform for standard JavaScript decorators in TypeScript code in the future. Such a transform has not been implemented yet, however.

    * TypeScript's `target` no longer affects esbuild's `target` ([#2628](https://github.com/evanw/esbuild/issues/2628))

        Some people requested that esbuild support TypeScript's `target` setting, so support for it was added (in [version 0.12.4](https://github.com/evanw/esbuild/releases/v0.12.4)). However, esbuild supports reading from multiple `tsconfig.json` files within a single build, which opens up the possibility that different files in the build have different language targets configured. There isn't really any reason to do this and it can lead to unexpected results. So with this release, the `target` setting in `tsconfig.json` will no longer affect esbuild's own `target` setting. You will have to use esbuild's own target setting instead (which is a single, global value).

    * TypeScript's `jsx` setting no longer causes esbuild to preserve JSX syntax ([#2634](https://github.com/evanw/esbuild/issues/2634))

        TypeScript has a setting called [`jsx`](https://www.typescriptlang.org/tsconfig#jsx) that controls how to transform JSX into JS. The tool-agnostic transform is called `react`, and the React-specific transform is called `react-jsx` (or `react-jsxdev`). There is also a setting called `preserve` which indicates JSX should be passed through untransformed. Previously people would run esbuild with `"jsx": "preserve"` in their `tsconfig.json` files and then be surprised when esbuild preserved their JSX. So with this release, esbuild will now ignore `"jsx": "preserve"` in `tsconfig.json` files. If you want to preserve JSX syntax with esbuild, you now have to use `--jsx=preserve`.

        Note: Some people have suggested that esbuild's equivalent `jsx` setting override the one in `tsconfig.json`. However, some projects need to legitimately have different files within the same build use different transforms (i.e. `react` vs. `react-jsx`) and having esbuild's global `jsx` setting override `tsconfig.json` would prevent this from working. This release ignores `"jsx": "preserve"` but still allows other `jsx` values in `tsconfig.json` files to override esbuild's global `jsx` setting to keep the ability for multiple files within the same build to use different transforms.

    * `useDefineForClassFields` behavior has changed ([#2584](https://github.com/evanw/esbuild/issues/2584), [#2993](https://github.com/evanw/esbuild/issues/2993))

        Class fields in TypeScript look like this (`x` is a class field):

        ```js
        class Foo {
          x = 123
        }
        ```

        TypeScript has legacy behavior that uses assignment semantics instead of define semantics for class fields when [`useDefineForClassFields`](https://www.typescriptlang.org/tsconfig#useDefineForClassFields) is enabled (in which case class fields in TypeScript behave differently than they do in JavaScript, which is arguably "wrong").

        This legacy behavior exists because TypeScript added class fields to TypeScript before they were added to JavaScript. The TypeScript team decided to go with assignment semantics and shipped their implementation. Much later on TC39 decided to go with define semantics for class fields in JavaScript instead. This behaves differently if the base class has a setter with the same name:

        ```js
        class Base {
          set x(_) {
            console.log('x:', _)
          }
        }

        // useDefineForClassFields: false
        class AssignSemantics extends Base {
          constructor() {
            super()
            this.x = 123
          }
        }

        // useDefineForClassFields: true
        class DefineSemantics extends Base {
          constructor() {
            super()
            Object.defineProperty(this, 'x', { value: 123 })
          }
        }

        console.log(
          new AssignSemantics().x, // Calls the setter
          new DefineSemantics().x // Doesn't call the setter
        )
        ```

        When you run `tsc`, the value of `useDefineForClassFields` defaults to `false` when it's not specified and the `target` in `tsconfig.json` is present but earlier than `ES2022`. This sort of makes sense because the class field language feature was added in ES2022, so before ES2022 class fields didn't exist (and thus TypeScript's legacy behavior is active). However, TypeScript's `target` setting currently defaults to `ES3` which unfortunately means that the `useDefineForClassFields` setting currently defaults to false (i.e. to "wrong"). In other words if you run `tsc` with all default settings, class fields will behave incorrectly.

        Previously esbuild tried to do what `tsc` did. That meant esbuild's version of `useDefineForClassFields` was `false` by default, and was also `false` if esbuild's `--target=` was present but earlier than `es2022`. However, TypeScript's legacy class field behavior is becoming increasingly irrelevant and people who expect class fields in TypeScript to work like they do in JavaScript are confused when they use esbuild with default settings. It's also confusing that the behavior of class fields would change if you changed the language target (even though that's exactly how TypeScript works).

        So with this release, esbuild will now only use the information in `tsconfig.json` to determine whether `useDefineForClassFields` is true or not. Specifically `useDefineForClassFields` will be respected if present, otherwise it will be `false` if `target` is present in `tsconfig.json` and is `ES2021` or earlier, otherwise it will be `true`. Targets passed to esbuild's `--target=` setting will no longer affect `useDefineForClassFields`.

        Note that this means different directories in your build can have different values for this setting since esbuild allows different directories to have different `tsconfig.json` files within the same build. This should let you migrate your code one directory at a time without esbuild's `--target=` setting affecting the semantics of your code.

    * Add support for `verbatimModuleSyntax` from TypeScript 5.0

        TypeScript 5.0 added a new option called [`verbatimModuleSyntax`](https://www.typescriptlang.org/tsconfig#verbatimModuleSyntax) that deprecates and replaces two older options, `preserveValueImports` and `importsNotUsedAsValues`. Setting `verbatimModuleSyntax` to true in `tsconfig.json` tells esbuild to not drop unused import statements. Specifically esbuild now treats `"verbatimModuleSyntax": true` as if you had specified both `"preserveValueImports": true` and `"importsNotUsedAsValues": "preserve"`.

    * Add multiple inheritance for `tsconfig.json` from TypeScript 5.0

        TypeScript 5.0 now allows [multiple inheritance for `tsconfig.json` files](https://devblogs.microsoft.com/typescript/announcing-typescript-5-0/#supporting-multiple-configuration-files-in-extends). You can now pass an array of filenames via the `extends` parameter and your `tsconfig.json` will start off containing properties from all of those configuration files, in order. This release of esbuild adds support for this new TypeScript feature.

    * Remove support for `moduleSuffixes` ([#2395](https://github.com/evanw/esbuild/issues/2395))

        The community has requested that esbuild remove support for TypeScript's `moduleSuffixes` feature, so it has been removed in this release. Instead you can use esbuild's `--resolve-extensions=` feature to select which module suffix you want to build with.

    * Apply `--tsconfig=` overrides to `stdin` and virtual files ([#385](https://github.com/evanw/esbuild/issues/385), [#2543](https://github.com/evanw/esbuild/issues/2543))

        When you override esbuild's automatic `tsconfig.json` file detection with `--tsconfig=` to pass a specific `tsconfig.json` file, esbuild previously didn't apply these settings to source code passed via the `stdin` API option or to TypeScript files from plugins that weren't in the `file` namespace. This release changes esbuild's behavior so that settings from `tsconfig.json` also apply to these source code files as well.

    * Support `--tsconfig-raw=` in build API calls ([#943](https://github.com/evanw/esbuild/issues/943), [#2440](https://github.com/evanw/esbuild/issues/2440))

        Previously if you wanted to override esbuild's automatic `tsconfig.json` file detection, you had to create a new `tsconfig.json` file and pass the file name to esbuild via the `--tsconfig=` flag. With this release, you can now optionally use `--tsconfig-raw=` instead to pass the contents of `tsconfig.json` to esbuild directly instead of passing the file name. For example, you can now use `--tsconfig-raw={"compilerOptions":{"experimentalDecorators":true}}` to enable TypeScript experimental decorators directly using a command-line flag (assuming you escape the quotes correctly using your current shell's quoting rules). The `--tsconfig-raw=` flag previously only worked with transform API calls but with this release, it now works with build API calls too.

    * Ignore all `tsconfig.json` files in `node_modules` ([#276](https://github.com/evanw/esbuild/issues/276), [#2386](https://github.com/evanw/esbuild/issues/2386))

        This changes esbuild's behavior that applies `tsconfig.json` to all files in the subtree of the directory containing `tsconfig.json`. In version 0.12.7, esbuild started ignoring `tsconfig.json` files inside `node_modules` folders. The rationale is that people typically do this by mistake and that doing this intentionally is a rare use case that doesn't need to be supported. However, this change only applied to certain syntax-specific settings (e.g. `jsxFactory`) but did not apply to path resolution settings (e.g. `paths`). With this release, esbuild will now ignore all `tsconfig.json` files in `node_modules` instead of only ignoring certain settings.

    * Ignore `tsconfig.json` when resolving paths within `node_modules` ([#2481](https://github.com/evanw/esbuild/issues/2481))

        Previously fields in `tsconfig.json` related to path resolution (e.g. `paths`) were respected for all files in the subtree containing that `tsconfig.json` file, even within a nested `node_modules` subdirectory. This meant that a project's `paths` settings could potentially affect any bundled packages. With this release, esbuild will no longer use `tsconfig.json` settings during path resolution inside nested `node_modules` subdirectories.

    * Prefer `.js` over `.ts` within `node_modules` ([#3019](https://github.com/evanw/esbuild/issues/3019))

        The default list of implicit extensions that esbuild will try appending to import paths contains `.ts` before `.js`. This makes it possible to bundle TypeScript projects that reference other files in the project using extension-less imports (e.g. `./some-file` to load `./some-file.ts` instead of `./some-file.js`). However, this behavior is undesirable within `node_modules` directories. Some package authors publish both their original TypeScript code and their compiled JavaScript code side-by-side. In these cases, esbuild should arguably be using the compiled JavaScript files instead of the original TypeScript files because the TypeScript compilation settings for files within the package should be determined by the package author, not the user of esbuild. So with this release, esbuild will now prefer implicit `.js` extensions over `.ts` when searching for import paths within `node_modules`.

    These changes are intended to improve esbuild's compatibility with `tsc` and reduce the number of unfortunate behaviors regarding `tsconfig.json` and esbuild.

* Add a workaround for bugs in Safari 16.2 and earlier ([#3072](https://github.com/evanw/esbuild/issues/3072))

    Safari's JavaScript parser had a bug (which has now been fixed) where at least something about unary/binary operators nested inside default arguments nested inside either a function or class expression was incorrectly considered a syntax error if that expression was the target of a property assignment. Here are some examples that trigger this Safari bug:

    ```
    ❱ x(function (y = -1) {}.z = 2)
    SyntaxError: Left hand side of operator '=' must be a reference.

    ❱ x(class { f(y = -1) {} }.z = 2)
    SyntaxError: Left hand side of operator '=' must be a reference.
    ```

    It's not clear what the exact conditions are that trigger this bug. However, a workaround for this bug appears to be to post-process your JavaScript to wrap any in function and class declarations that are the direct target of a property access expression in parentheses. That's the workaround that UglifyJS applies for this issue: [mishoo/UglifyJS#2056](https://github.com/mishoo/UglifyJS/pull/2056). So that's what esbuild now does starting with this release:

    ```js
    // Original code
    x(function (y = -1) {}.z = 2, class { f(y = -1) {} }.z = 2)

    // Old output (with --minify --target=safari16.2)
    x(function(c=-1){}.z=2,class{f(c=-1){}}.z=2);

    // New output (with --minify --target=safari16.2)
    x((function(c=-1){}).z=2,(class{f(c=-1){}}).z=2);
    ```

    This fix is not enabled by default. It's only enabled when `--target=` contains Safari 16.2 or earlier, such as with `--target=safari16.2`. You can also explicitly enable or disable this specific transform (called `function-or-class-property-access`) with `--supported:function-or-class-property-access=false`.

* Fix esbuild's TypeScript type declarations to forbid unknown properties ([#3089](https://github.com/evanw/esbuild/issues/3089))

    Version 0.17.0 of esbuild introduced a specific form of function overloads in the TypeScript type definitions for esbuild's API calls that looks like this:

    ```ts
    interface TransformOptions {
      legalComments?: 'none' | 'inline' | 'eof' | 'external'
    }

    interface TransformResult<ProvidedOptions extends TransformOptions = TransformOptions> {
      legalComments: string | (ProvidedOptions['legalComments'] extends 'external' ? never : undefined)
    }

    declare function transformSync<ProvidedOptions extends TransformOptions>(input: string, options?: ProvidedOptions): TransformResult<ProvidedOptions>
    declare function transformSync(input: string, options?: TransformOptions): TransformResult
    ```

    This more accurately reflects how esbuild's JavaScript API behaves. The result object returned by `transformSync` only has the `legalComments` property if you pass `legalComments: 'external'`:

    ```ts
    // These have type "string | undefined"
    transformSync('').legalComments
    transformSync('', { legalComments: 'eof' }).legalComments

    // This has type "string"
    transformSync('', { legalComments: 'external' }).legalComments
    ```

    However, this form of function overloads unfortunately allows typos (e.g. `egalComments`) to pass the type checker without generating an error as TypeScript allows all objects with unknown properties to extend `TransformOptions`. These typos result in esbuild's API throwing an error at run-time.

    To prevent typos during type checking, esbuild's TypeScript type definitions will now use a different form that looks like this:

    ```ts
    type SameShape<Out, In extends Out> = In & { [Key in Exclude<keyof In, keyof Out>]: never }

    interface TransformOptions {
      legalComments?: 'none' | 'inline' | 'eof' | 'external'
    }

    interface TransformResult<ProvidedOptions extends TransformOptions = TransformOptions> {
      legalComments: string | (ProvidedOptions['legalComments'] extends 'external' ? never : undefined)
    }

    declare function transformSync<T extends TransformOptions>(input: string, options?: SameShape<TransformOptions, T>): TransformResult<T>
    ```

    This change should hopefully not affect correct code. It should hopefully introduce type errors only for incorrect code.

* Fix CSS nesting transform for pseudo-elements ([#3119](https://github.com/evanw/esbuild/issues/3119))

    This release fixes esbuild's CSS nesting transform for pseudo-elements (e.g. `::before` and `::after`). The CSS nesting specification says that [the nesting selector does not work with pseudo-elements](https://www.w3.org/TR/css-nesting-1/#ref-for-matches-pseudo%E2%91%A0). This can be seen in the example below: esbuild does not carry the parent pseudo-element `::before` through the nesting selector `&`. However, that doesn't apply to pseudo-elements that are within the same selector. Previously esbuild had a bug where it considered pseudo-elements in both locations as invalid. This release changes esbuild to only consider those from the parent selector invalid, which should align with the specification:

    ```css
    /* Original code */
    a, b::before {
      &.c, &::after {
        content: 'd';
      }
    }

    /* Old output (with --target=chrome90) */
    a:is(.c, ::after) {
      content: "d";
    }

    /* New output (with --target=chrome90) */
    a.c,
    a::after {
      content: "d";
    }
    ```

* Forbid `&` before a type selector in nested CSS

    The people behind the work-in-progress CSS nesting specification have very recently [decided to forbid nested CSS that looks like `&div`](https://github.com/w3c/csswg-drafts/issues/8662#issuecomment-1514977935). You will have to use either `div&` or `&:is(div)` instead. This release of esbuild has been updated to take this new change into consideration. Doing this now generates a warning. The suggested fix is slightly different depending on where in the overall selector it happened:

    ```
    ▲ [WARNING] Cannot use type selector "input" directly after nesting selector "&" [css-syntax-error]

        example.css:2:3:
          2 │   &input {
            │    ~~~~~
            ╵    :is(input)

      CSS nesting syntax does not allow the "&" selector to come before a type selector. You can wrap
      this selector in ":is()" as a workaround. This restriction exists to avoid problems with SASS
      nesting, where the same syntax means something very different that has no equivalent in real CSS
      (appending a suffix to the parent selector).

    ▲ [WARNING] Cannot use type selector "input" directly after nesting selector "&" [css-syntax-error]

        example.css:6:8:
          6 │   .form &input {
            │         ~~~~~~
            ╵         input&

      CSS nesting syntax does not allow the "&" selector to come before a type selector. You can move
      the "&" to the end of this selector as a workaround. This restriction exists to avoid problems
      with SASS nesting, where the same syntax means something very different that has no equivalent in
      real CSS (appending a suffix to the parent selector).
    ```

## 0.17.19

* Fix CSS transform bugs with nested selectors that start with a combinator ([#3096](https://github.com/evanw/esbuild/issues/3096))

    This release fixes several bugs regarding transforming nested CSS into non-nested CSS for older browsers. The bugs were due to lack of test coverage for nested selectors with more than one compound selector where they all start with the same combinator. Here's what some problematic cases look like before and after these fixes:

    ```css
    /* Original code */
    .foo {
      > &a,
      > &b {
        color: red;
      }
    }
    .bar {
      > &a,
      + &b {
        color: green;
      }
    }

    /* Old output (with --target=chrome90) */
    .foo :is(> .fooa, > .foob) {
      color: red;
    }
    .bar :is(> .bara, + .barb) {
      color: green;
    }

    /* New output (with --target=chrome90) */
    .foo > :is(a.foo, b.foo) {
      color: red;
    }
    .bar > a.bar,
    .bar + b.bar {
      color: green;
    }
    ```

* Fix bug with TypeScript parsing of instantiation expressions followed by `=` ([#3111](https://github.com/evanw/esbuild/issues/3111))

    This release fixes esbuild's TypeScript-to-JavaScript conversion code in the case where a potential instantiation expression is followed immediately by a `=` token (such that the trailing `>` becomes a `>=` token). Previously esbuild considered that to still be an instantiation expression, but the official TypeScript compiler considered it to be a `>=` operator instead. This release changes esbuild's interpretation to match TypeScript. This edge case currently [appears to be problematic](https://sucrase.io/#transforms=typescript&compareWithTypeScript=true&code=x%3Cy%3E%3Da%3Cb%3Cc%3E%3E()) for other TypeScript-to-JavaScript converters as well:

    | Original code | TypeScript | esbuild 0.17.18 | esbuild 0.17.19 | Sucrase | Babel |
    |---|---|---|---|---|---|
    | `x<y>=a<b<c>>()` | `x<y>=a();` | `x=a();` | `x<y>=a();` | `x=a()` | Invalid left-hand side in assignment expression |

* Avoid removing unrecognized directives from the directive prologue when minifying ([#3115](https://github.com/evanw/esbuild/issues/3115))

    The [directive prologue](https://262.ecma-international.org/6.0/#sec-directive-prologues-and-the-use-strict-directive) in JavaScript is a sequence of top-level string expressions that come before your code. The only directives that JavaScript engines currently recognize are `use strict` and sometimes `use asm`. However, the people behind React have made up their own directive for their own custom dialect of JavaScript. Previously esbuild only preserved the `use strict` directive when minifying, although you could still write React JavaScript with esbuild using something like `--banner:js="'your directive here';"`. With this release, you can now put arbitrary directives in the entry point and esbuild will preserve them in its minified output:

    ```js
    // Original code
    'use wtf'; console.log(123)

    // Old output (with --minify)
    console.log(123);

    // New output (with --minify)
    "use wtf";console.log(123);
    ```

    Note that this means esbuild will no longer remove certain stray top-level strings when minifying. This behavior is an intentional change because these stray top-level strings are actually part of the directive prologue, and could potentially have semantics assigned to them (as was the case with React).

* Improved minification of binary shift operators

    With this release, esbuild's minifier will now evaluate the `<<` and `>>>` operators if the resulting code would be shorter:

    ```js
    // Original code
    console.log(10 << 10, 10 << 20, -123 >>> 5, -123 >>> 10);

    // Old output (with --minify)
    console.log(10<<10,10<<20,-123>>>5,-123>>>10);

    // New output (with --minify)
    console.log(10240,10<<20,-123>>>5,4194303);
    ```

## 0.17.18

* Fix non-default JSON import error with `export {} from` ([#3070](https://github.com/evanw/esbuild/issues/3070))

    This release fixes a bug where esbuild incorrectly identified statements of the form `export { default as x } from "y" assert { type: "json" }` as a non-default import. The bug did not affect code of the form `import { default as x } from ...` (only code that used the `export` keyword).

* Fix a crash with an invalid subpath import ([#3067](https://github.com/evanw/esbuild/issues/3067))

    Previously esbuild could crash when attempting to generate a friendly error message for an invalid [subpath import](https://nodejs.org/api/packages.html#subpath-imports) (i.e. an import starting with `#`). This happened because esbuild originally only supported the `exports` field and the code for that error message was not updated when esbuild later added support for the `imports` field. This crash has been fixed.

## 0.17.17

* Fix CSS nesting transform for top-level `&` ([#3052](https://github.com/evanw/esbuild/issues/3052))

    Previously esbuild could crash with a stack overflow when lowering CSS nesting rules with a top-level `&`, such as in the code below. This happened because esbuild's CSS nesting transform didn't handle top-level `&`, causing esbuild to inline the top-level selector into itself. This release handles top-level `&` by replacing it with [the `:scope` pseudo-class](https://drafts.csswg.org/selectors-4/#the-scope-pseudo):

    ```css
    /* Original code */
    &,
    a {
      .b {
        color: red;
      }
    }

    /* New output (with --target=chrome90) */
    :is(:scope, a) .b {
      color: red;
    }
    ```

* Support `exports` in `package.json` for `extends` in `tsconfig.json` ([#3058](https://github.com/evanw/esbuild/issues/3058))

    TypeScript 5.0 added the ability to use `extends` in `tsconfig.json` to reference a path in a package whose `package.json` file contains an `exports` map that points to the correct location. This doesn't automatically work in esbuild because `tsconfig.json` affects esbuild's path resolution, so esbuild's normal path resolution logic doesn't apply.

    This release adds support for doing this by adding some additional code that attempts to resolve the `extends` path using the `exports` field. The behavior should be similar enough to esbuild's main path resolution logic to work as expected.

    Note that esbuild always treats this `extends` import as a `require()` import since that's what TypeScript appears to do. Specifically the `require` condition will be active and the `import` condition will be inactive.

* Fix watch mode with `NODE_PATH` ([#3062](https://github.com/evanw/esbuild/issues/3062))

    Node has a rarely-used feature where you can extend the set of directories that node searches for packages using the `NODE_PATH` environment variable. While esbuild supports this too, previously a bug prevented esbuild's watch mode from picking up changes to imported files that were contained directly in a `NODE_PATH` directory. You're supposed to use `NODE_PATH` for packages, but some people abuse this feature by putting files in that directory instead (e.g. `node_modules/some-file.js` instead of `node_modules/some-pkg/some-file.js`). The watch mode bug happens when you do this because esbuild first tries to read `some-file.js` as a directory and then as a file. Watch mode was incorrectly waiting for `some-file.js` to become a valid directory. This release fixes this edge case bug by changing watch mode to watch `some-file.js` as a file when this happens.

## 0.17.16

* Fix CSS nesting transform for triple-nested rules that start with a combinator ([#3046](https://github.com/evanw/esbuild/issues/3046))

    This release fixes a bug with esbuild where triple-nested CSS rules that start with a combinator were not transformed correctly for older browsers. Here's an example of such a case before and after this bug fix:

    ```css
    /* Original input */
    .a {
      color: red;
      > .b {
        color: green;
        > .c {
          color: blue;
        }
      }
    }

    /* Old output (with --target=chrome90) */
    .a {
      color: red;
    }
    .a > .b {
      color: green;
    }
    .a .b > .c {
      color: blue;
    }

    /* New output (with --target=chrome90) */
    .a {
      color: red;
    }
    .a > .b {
      color: green;
    }
    .a > .b > .c {
      color: blue;
    }
    ```

* Support `--inject` with a file loaded using the `copy` loader ([#3041](https://github.com/evanw/esbuild/issues/3041))

    This release now allows you to use `--inject` with a file that is loaded using the `copy` loader. The `copy` loader copies the imported file to the output directory verbatim and rewrites the path in the `import` statement to point to the copied output file. When used with `--inject`, this means the injected file will be copied to the output directory as-is and a bare `import` statement for that file will be inserted in any non-copy output files that esbuild generates.

    Note that since esbuild doesn't parse the contents of copied files, esbuild will not expose any of the export names as usable imports when you do this (in the way that esbuild's `--inject` feature is typically used). However, any side-effects that the injected file has will still occur.

## 0.17.15

* Allow keywords as type parameter names in mapped types ([#3033](https://github.com/evanw/esbuild/issues/3033))

    TypeScript allows type keywords to be used as parameter names in mapped types. Previously esbuild incorrectly treated this as an error. Code that does this is now supported:

    ```ts
    type Foo = 'a' | 'b' | 'c'
    type A = { [keyof in Foo]: number }
    type B = { [infer in Foo]: number }
    type C = { [readonly in Foo]: number }
    ```

* Add annotations for re-exported modules in node ([#2486](https://github.com/evanw/esbuild/issues/2486), [#3029](https://github.com/evanw/esbuild/issues/3029))

    Node lets you import named imports from a CommonJS module using ESM import syntax. However, the allowed names aren't derived from the properties of the CommonJS module. Instead they are derived from an arbitrary syntax-only analysis of the CommonJS module's JavaScript AST.

    To accommodate node doing this, esbuild's ESM-to-CommonJS conversion adds a special non-executable "annotation" for node that describes the exports that node should expose in this scenario. It takes the form `0 && (module.exports = { ... })` and comes at the end of the file (`0 && expr` means `expr` is never evaluated).

    Previously esbuild didn't do this for modules re-exported using the `export * from` syntax. Annotations for these re-exports will now be added starting with this release:

    ```js
    // Original input
    export { foo } from './foo'
    export * from './bar'

    // Old output (with --format=cjs --platform=node)
    ...
    0 && (module.exports = {
      foo
    });

    // New output (with --format=cjs --platform=node)
    ...
    0 && (module.exports = {
      foo,
      ...require("./bar")
    });
    ```

    Note that you need to specify both `--format=cjs` and `--platform=node` to get these node-specific annotations.

* Avoid printing an unnecessary space in between a number and a `.` ([#3026](https://github.com/evanw/esbuild/pull/3026))

    JavaScript typically requires a space in between a number token and a `.` token to avoid the `.` being interpreted as a decimal point instead of a member expression. However, this space is not required if the number token itself contains a decimal point, an exponent, or uses a base other than 10. This release of esbuild now avoids printing the unnecessary space in these cases:

    ```js
    // Original input
    foo(1000 .x, 0 .x, 0.1 .x, 0.0001 .x, 0xFFFF_0000_FFFF_0000 .x)

    // Old output (with --minify)
    foo(1e3 .x,0 .x,.1 .x,1e-4 .x,0xffff0000ffff0000 .x);

    // New output (with --minify)
    foo(1e3.x,0 .x,.1.x,1e-4.x,0xffff0000ffff0000.x);
    ```

* Fix server-sent events with live reload when writing to the file system root ([#3027](https://github.com/evanw/esbuild/issues/3027))

    This release fixes a bug where esbuild previously failed to emit server-sent events for live reload when `outdir` was the file system root, such as `/`. This happened because `/` is the only path on Unix that cannot have a trailing slash trimmed from it, which was fixed by improved path handling.

## 0.17.14

* Allow the TypeScript 5.0 `const` modifier in object type declarations ([#3021](https://github.com/evanw/esbuild/issues/3021))

    The new TypeScript 5.0 `const` modifier was added to esbuild in version 0.17.5, and works with classes, functions, and arrow expressions. However, support for it wasn't added to object type declarations (e.g. interfaces) due to an oversight. This release adds support for these cases, so the following TypeScript 5.0 code can now be built with esbuild:

    ```ts
    interface Foo { <const T>(): T }
    type Bar = { new <const T>(): T }
    ```

* Implement preliminary lowering for CSS nesting ([#1945](https://github.com/evanw/esbuild/issues/1945))

    Chrome has [implemented the new CSS nesting specification](https://developer.chrome.com/articles/css-nesting/) in version 112, which is currently in beta but will become stable very soon. So CSS nesting is now a part of the web platform!

    This release of esbuild can now transform nested CSS syntax into non-nested CSS syntax for older browsers. The transformation relies on the `:is()` pseudo-class in many cases, so the transformation is only guaranteed to work when targeting browsers that support `:is()` (e.g. Chrome 88+). You'll need to set esbuild's [`target`](https://esbuild.github.io/api/#target) to the browsers you intend to support to tell esbuild to do this transformation. You will get a warning if you use CSS nesting syntax with a `target` which includes older browsers that don't support `:is()`.

    The lowering transformation looks like this:

    ```css
    /* Original input */
    a.btn {
      color: #333;
      &:hover { color: #444 }
      &:active { color: #555 }
    }

    /* New output (with --target=chrome88) */
    a.btn {
      color: #333;
    }
    a.btn:hover {
      color: #444;
    }
    a.btn:active {
      color: #555;
    }
    ```

    More complex cases may generate the `:is()` pseudo-class:

    ```css
    /* Original input */
    div, p {
      .warning, .error {
        padding: 20px;
      }
    }

    /* New output (with --target=chrome88) */
    :is(div, p) :is(.warning, .error) {
      padding: 20px;
    }
    ```

    In addition, esbuild now has a special warning message for nested style rules that start with an identifier. This isn't allowed in CSS because the syntax would be ambiguous with the existing declaration syntax. The new warning message looks like this:

    ```
    ▲ [WARNING] A nested style rule cannot start with "p" because it looks like the start of a declaration [css-syntax-error]

        <stdin>:1:7:
          1 │ main { p { margin: auto } }
            │        ^
            ╵        :is(p)

      To start a nested style rule with an identifier, you need to wrap the identifier in ":is(...)" to
      prevent the rule from being parsed as a declaration.
    ```

    Keep in mind that the transformation in this release is a preliminary implementation. CSS has many features that interact in complex ways, and there may be some edge cases that don't work correctly yet.

* Minification now removes unnecessary `&` CSS nesting selectors

    This release introduces the following CSS minification optimizations:

    ```css
    /* Original input */
    a {
      font-weight: bold;
      & {
        color: blue;
      }
      & :hover {
        text-decoration: underline;
      }
    }

    /* Old output (with --minify) */
    a{font-weight:700;&{color:#00f}& :hover{text-decoration:underline}}

    /* New output (with --minify) */
    a{font-weight:700;:hover{text-decoration:underline}color:#00f}
    ```

* Minification now removes duplicates from CSS selector lists

    This release introduces the following CSS minification optimization:

    ```css
    /* Original input */
    div, div { color: red }

    /* Old output (with --minify) */
    div,div{color:red}

    /* New output (with --minify) */
    div{color:red}
    ```

## 0.17.13

* Work around an issue with `NODE_PATH` and Go's WebAssembly internals ([#3001](https://github.com/evanw/esbuild/issues/3001))

    Go's WebAssembly implementation returns `EINVAL` instead of `ENOTDIR` when using the `readdir` syscall on a file. This messes up esbuild's implementation of node's module resolution algorithm since encountering `ENOTDIR` causes esbuild to continue its search (since it's a normal condition) while other encountering other errors causes esbuild to fail with an I/O error (since it's an unexpected condition). You can encounter this issue in practice if you use node's legacy `NODE_PATH` feature to tell esbuild to resolve node modules in a custom directory that was not installed by npm. This release works around this problem by converting `EINVAL` into `ENOTDIR` for the `readdir` syscall.

* Fix a minification bug with CSS `@layer` rules that have parsing errors ([#3016](https://github.com/evanw/esbuild/issues/3016))

    CSS at-rules [require either a `{}` block or a semicolon at the end](https://www.w3.org/TR/css-syntax-3/#consume-at-rule). Omitting both of these causes esbuild to treat the rule as an unknown at-rule. Previous releases of esbuild had a bug that incorrectly removed unknown at-rules without any children during minification if the at-rule token matched an at-rule that esbuild can handle. Specifically [cssnano](https://cssnano.co/) can generate `@layer` rules with parsing errors, and empty `@layer` rules cannot be removed because they have side effects (`@layer` didn't exist when esbuild's CSS support was added, so esbuild wasn't written to handle this). This release changes esbuild to no longer discard `@layer` rules with parsing errors when minifying (the rule `@layer c` has a parsing error):

    ```css
    /* Original input */
    @layer a {
      @layer b {
        @layer c
      }
    }

    /* Old output (with --minify) */
    @layer a.b;

    /* New output (with --minify) */
    @layer a.b.c;
    ```

* Unterminated strings in CSS are no longer an error

    The CSS specification provides [rules for handling parsing errors](https://www.w3.org/TR/CSS22/syndata.html#parsing-errors). One of those rules is that user agents must close strings upon reaching the end of a line (i.e., before an unescaped line feed, carriage return or form feed character), but then drop the construct (declaration or rule) in which the string was found. For example:

    ```css
    p {
      color: green;
      font-family: 'Courier New Times
      color: red;
      color: green;
    }
    ```

    ...would be treated the same as:

    ```css
    p { color: green; color: green; }
    ```

    ...because the second declaration (from `font-family` to the semicolon after `color: red`) is invalid and is dropped.

    Previously using this CSS with esbuild failed to build due to a syntax error, even though the code can be interpreted by a browser. With this release, the code now produces a warning instead of an error, and esbuild prints the invalid CSS such that it stays invalid in the output:

    ```css
    /* esbuild's new non-minified output: */
    p {
      color: green;
      font-family: 'Courier New Times
      color: red;
      color: green;
    }
    ```

    ```css
    /* esbuild's new minified output: */
    p{font-family:'Courier New Times
    color: red;color:green}
    ```

## 0.17.12

* Fix a crash when parsing inline TypeScript decorators ([#2991](https://github.com/evanw/esbuild/issues/2991))

    Previously esbuild's TypeScript parser crashed when parsing TypeScript decorators if the definition of the decorator was inlined into the decorator itself:

    ```ts
    @(function sealed(constructor: Function) {
      Object.seal(constructor);
      Object.seal(constructor.prototype);
    })
    class Foo {}
    ```

    This crash was not noticed earlier because this edge case did not have test coverage. The crash is fixed in this release.

## 0.17.11

* Fix the `alias` feature to always prefer the longest match ([#2963](https://github.com/evanw/esbuild/issues/2963))

    It's possible to configure conflicting aliases such as `--alias:a=b` and `--alias:a/c=d`, which is ambiguous for the import path `a/c/x` (since it could map to either `b/c/x` or `d/x`). Previously esbuild would pick the first matching `alias`, which would non-deterministically pick between one of the possible matches. This release fixes esbuild to always deterministically pick the longest possible match.

* Minify calls to some global primitive constructors ([#2962](https://github.com/evanw/esbuild/issues/2962))

    With this release, esbuild's minifier now replaces calls to `Boolean`/`Number`/`String`/`BigInt` with equivalent shorter code when relevant:

    ```js
    // Original code
    console.log(
      Boolean(a ? (b | c) !== 0 : (c & d) !== 0),
      Number(e ? '1' : '2'),
      String(e ? '1' : '2'),
      BigInt(e ? 1n : 2n),
    )

    // Old output (with --minify)
    console.log(Boolean(a?(b|c)!==0:(c&d)!==0),Number(e?"1":"2"),String(e?"1":"2"),BigInt(e?1n:2n));

    // New output (with --minify)
    console.log(!!(a?b|c:c&d),+(e?"1":"2"),e?"1":"2",e?1n:2n);
    ```

* Adjust some feature compatibility tables for node ([#2940](https://github.com/evanw/esbuild/issues/2940))

    This release makes the following adjustments to esbuild's internal feature compatibility tables for node, which tell esbuild which versions of node are known to support all aspects of that feature:

    * `class-private-brand-checks`: node v16.9+ => node v16.4+ (a decrease)
    * `hashbang`: node v12.0+ => node v12.5+ (an increase)
    * `optional-chain`: node v16.9+ => node v16.1+ (a decrease)
    * `template-literal`: node v4+ => node v10+ (an increase)

    Each of these adjustments was identified by comparing against data from the `node-compat-table` package and was manually verified using old node executables downloaded from https://nodejs.org/download/release/.

## 0.17.10

* Update esbuild's handling of CSS nesting to match the latest specification changes ([#1945](https://github.com/evanw/esbuild/issues/1945))

    The syntax for the upcoming CSS nesting feature has [recently changed](https://webkit.org/blog/13813/try-css-nesting-today-in-safari-technology-preview/). The `@nest` prefix that was previously required in some cases is now gone, and nested rules no longer have to start with `&` (as long as they don't start with an identifier or function token).

    This release updates esbuild's pass-through handling of CSS nesting syntax to match the latest specification changes. So you can now use esbuild to bundle CSS containing nested rules and try them out in a browser that supports CSS nesting (which includes nightly builds of both Chrome and Safari).

    However, I'm not implementing lowering of nested CSS to non-nested CSS for older browsers yet. While the syntax has been decided, the semantics are still in flux. In particular, there is still some debate about changing the fundamental way that CSS nesting works. For example, you might think that the following CSS is equivalent to a `.outer .inner button { ... }` rule:

    ```css
    .inner button {
      .outer & {
        color: red;
      }
    }
    ```

    But instead it's actually equivalent to a `.outer :is(.inner button) { ... }` rule which unintuitively also matches the following DOM structure:

    ```html
    <div class="inner">
      <div class="outer">
        <button></button>
      </div>
    </div>
    ```

    The `:is()` behavior is preferred by browser implementers because it's more memory-efficient, but the straightforward translation into a `.outer .inner button { ... }` rule is preferred by developers used to the existing CSS preprocessing ecosystem (e.g. SASS). It seems premature to commit esbuild to specific semantics for this syntax at this time given the ongoing debate.

* Fix cross-file CSS rule deduplication involving `url()` tokens ([#2936](https://github.com/evanw/esbuild/issues/2936))

    Previously cross-file CSS rule deduplication didn't handle `url()` tokens correctly. These tokens contain references to import paths which may be internal (i.e. in the bundle) or external (i.e. not in the bundle). When comparing two `url()` tokens for equality, the underlying import paths should be compared instead of their references. This release of esbuild fixes `url()` token comparisons. One side effect is that `@font-face` rules should now be deduplicated correctly across files:

    ```css
    /* Original code */
    @import "data:text/css, \
      @import 'http://example.com/style.css'; \
      @font-face { src: url(http://example.com/font.ttf) }";
    @import "data:text/css, \
      @font-face { src: url(http://example.com/font.ttf) }";

    /* Old output (with --bundle --minify) */
    @import"http://example.com/style.css";@font-face{src:url(http://example.com/font.ttf)}@font-face{src:url(http://example.com/font.ttf)}

    /* New output (with --bundle --minify) */
    @import"http://example.com/style.css";@font-face{src:url(http://example.com/font.ttf)}
    ```

## 0.17.9

* Parse rest bindings in TypeScript types ([#2937](https://github.com/evanw/esbuild/issues/2937))

    Previously esbuild was unable to parse the following valid TypeScript code:

    ```ts
    let tuple: (...[e1, e2, ...es]: any) => any
    ```

    This release includes support for parsing code like this.

* Fix TypeScript code translation for certain computed `declare` class fields ([#2914](https://github.com/evanw/esbuild/issues/2914))

    In TypeScript, the key of a computed `declare` class field should only be preserved if there are no decorators for that field. Previously esbuild always preserved the key, but esbuild will now remove the key to match the output of the TypeScript compiler:

    ```ts
    // Original code
    declare function dec(a: any, b: any): any
    declare const removeMe: unique symbol
    declare const keepMe: unique symbol
    class X {
        declare [removeMe]: any
        @dec declare [keepMe]: any
    }

    // Old output
    var _a;
    class X {
    }
    removeMe, _a = keepMe;
    __decorateClass([
      dec
    ], X.prototype, _a, 2);

    // New output
    var _a;
    class X {
    }
    _a = keepMe;
    __decorateClass([
      dec
    ], X.prototype, _a, 2);
    ```

* Fix a crash with path resolution error generation ([#2913](https://github.com/evanw/esbuild/issues/2913))

    In certain situations, a module containing an invalid import path could previously cause esbuild to crash when it attempts to generate a more helpful error message. This crash has been fixed.

## 0.17.8

* Fix a minification bug with non-ASCII identifiers ([#2910](https://github.com/evanw/esbuild/issues/2910))

    This release fixes a bug with esbuild where non-ASCII identifiers followed by a keyword were incorrectly not separated by a space. This bug affected both the `in` and `instanceof` keywords. Here's an example of the fix:

    ```js
    // Original code
    π in a

    // Old output (with --minify --charset=utf8)
    πin a;

    // New output (with --minify --charset=utf8)
    π in a;
    ```

* Fix a regression with esbuild's WebAssembly API in version 0.17.6 ([#2911](https://github.com/evanw/esbuild/issues/2911))

    Version 0.17.6 of esbuild updated the Go toolchain to version 1.20.0. This had the unfortunate side effect of increasing the amount of stack space that esbuild uses (presumably due to some changes to Go's WebAssembly implementation) which could cause esbuild's WebAssembly-based API to crash with a stack overflow in cases where it previously didn't crash. One such case is the package `grapheme-splitter` which contains code that looks like this:

    ```js
    if (
      (0x0300 <= code && code <= 0x036F) ||
      (0x0483 <= code && code <= 0x0487) ||
      (0x0488 <= code && code <= 0x0489) ||
      (0x0591 <= code && code <= 0x05BD) ||
      // ... many hundreds of lines later ...
    ) {
      return;
    }
    ```

    This edge case involves a chain of binary operators that results in an AST over 400 nodes deep. Normally this wouldn't be a problem because Go has growable call stacks, so the call stack would just grow to be as large as needed. However, WebAssembly byte code deliberately doesn't expose the ability to manipulate the stack pointer, so Go's WebAssembly translation is forced to use the fixed-size WebAssembly call stack. So esbuild's WebAssembly implementation is vulnerable to stack overflow in cases like these.

    It's not unreasonable for this to cause a stack overflow, and for esbuild's answer to this problem to be "don't write code like this." That's how many other AST-manipulation tools handle this problem. However, it's possible to implement AST traversal using iteration instead of recursion to work around limited call stack space. This version of esbuild implements this code transformation for esbuild's JavaScript parser and printer, so esbuild's WebAssembly implementation is now able to process the `grapheme-splitter` package (at least when compiled with Go 1.20.0 and run with node's WebAssembly implementation).

## 0.17.7

* Change esbuild's parsing of TypeScript instantiation expressions to match TypeScript 4.8+ ([#2907](https://github.com/evanw/esbuild/issues/2907))

    This release updates esbuild's implementation of instantiation expression erasure to match [microsoft/TypeScript#49353](https://github.com/microsoft/TypeScript/pull/49353). The new rules are as follows (copied from TypeScript's PR description):

    > When a potential type argument list is followed by
    >
    > * a line break,
    > * an `(` token,
    > * a template literal string, or
    > * any token except `<` or `>` that isn't the start of an expression,
    >
    > we consider that construct to be a type argument list. Otherwise we consider the construct to be a `<` relational expression followed by a `>` relational expression.

* Ignore `sideEffects: false` for imported CSS files ([#1370](https://github.com/evanw/esbuild/issues/1370), [#1458](https://github.com/evanw/esbuild/pull/1458), [#2905](https://github.com/evanw/esbuild/issues/2905))

    This release ignores the `sideEffects` annotation in `package.json` for CSS files that are imported into JS files using esbuild's `css` loader. This means that these CSS files are no longer be tree-shaken.

    Importing CSS into JS causes esbuild to automatically create a CSS entry point next to the JS entry point containing the bundled CSS. Previously packages that specified some form of `"sideEffects": false` could potentially cause esbuild to consider one or more of the JS files on the import path to the CSS file to be side-effect free, which would result in esbuild removing that CSS file from the bundle. This was problematic because the removal of that CSS is outwardly observable, since all CSS is global, so it was incorrect for previous versions of esbuild to tree-shake CSS files imported into JS files.

* Add constant folding for certain additional equality cases ([#2394](https://github.com/evanw/esbuild/issues/2394), [#2895](https://github.com/evanw/esbuild/issues/2895))

    This release adds constant folding for expressions similar to the following:

    ```js
    // Original input
    console.log(
      null === 'foo',
      null === undefined,
      null == undefined,
      false === 0,
      false == 0,
      1 === true,
      1 == true,
    )

    // Old output
    console.log(
      null === "foo",
      null === void 0,
      null == void 0,
      false === 0,
      false == 0,
      1 === true,
      1 == true
    );

    // New output
    console.log(
      false,
      false,
      true,
      false,
      true,
      false,
      true
    );
    ```

## 0.17.6

* Fix a CSS parser crash on invalid CSS ([#2892](https://github.com/evanw/esbuild/issues/2892))

    Previously the following invalid CSS caused esbuild's parser to crash:

    ```css
    @media screen
    ```

    The crash was caused by trying to construct a helpful error message assuming that there was an opening `{` token, which is not the case here. This release fixes the crash.

* Inline TypeScript enums that are referenced before their declaration

    Previously esbuild inlined enums within a TypeScript file from top to bottom, which meant that references to TypeScript enum members were only inlined within the same file if they came after the enum declaration. With this release, esbuild will now inline enums even when they are referenced before they are declared:

    ```ts
    // Original input
    export const foo = () => Foo.FOO
    const enum Foo { FOO = 0 }

    // Old output (with --tree-shaking=true)
    export const foo = () => Foo.FOO;
    var Foo = /* @__PURE__ */ ((Foo2) => {
      Foo2[Foo2["FOO"] = 0] = "FOO";
      return Foo2;
    })(Foo || {});

    // New output (with --tree-shaking=true)
    export const foo = () => 0 /* FOO */;
    ```

    This makes esbuild's TypeScript output smaller and faster when processing code that does this. I noticed this issue when I ran the TypeScript compiler's source code through esbuild's bundler. Now that the TypeScript compiler is going to be bundled with esbuild in the upcoming TypeScript 5.0 release, improvements like this will also improve the TypeScript compiler itself!

* Fix esbuild installation on Arch Linux ([#2785](https://github.com/evanw/esbuild/issues/2785), [#2812](https://github.com/evanw/esbuild/issues/2812), [#2865](https://github.com/evanw/esbuild/issues/2865))

    Someone made an unofficial `esbuild` package for Linux that adds the `ESBUILD_BINARY_PATH=/usr/bin/esbuild` environment variable to the user's default environment. This breaks all npm installations of esbuild for users with this unofficial Linux package installed, which has affected many people. Most (all?) people who encounter this problem haven't even installed this unofficial package themselves; instead it was installed for them as a dependency of another Linux package. The problematic change to add the `ESBUILD_BINARY_PATH` environment variable was reverted in the latest version of this unofficial package. However, old versions of this unofficial package are still there and will be around forever. With this release, `ESBUILD_BINARY_PATH` is now ignored by esbuild's install script when it's set to the value `/usr/bin/esbuild`. This should unbreak using npm to install `esbuild` in these problematic Linux environments.

    Note: The `ESBUILD_BINARY_PATH` variable is an undocumented way to override the location of esbuild's binary when esbuild's npm package is installed, which is necessary to substitute your own locally-built esbuild binary when debugging esbuild's npm package. It's only meant for very custom situations and should absolutely not be forced on others by default, especially without their knowledge. I may remove the code in esbuild's installer that reads `ESBUILD_BINARY_PATH` in the future to prevent these kinds of issues. It will unfortunately make debugging esbuild harder. If `ESBUILD_BINARY_PATH` is ever removed, it will be done in a "breaking change" release.

## 0.17.5

* Parse `const` type parameters from TypeScript 5.0

    The TypeScript 5.0 beta announcement adds [`const` type parameters](https://devblogs.microsoft.com/typescript/announcing-typescript-5-0-beta/#const-type-parameters) to the language. You can now add the `const` modifier on a type parameter of a function, method, or class like this:

    ```ts
    type HasNames = { names: readonly string[] };
    const getNamesExactly = <const T extends HasNames>(arg: T): T["names"] => arg.names;
    const names = getNamesExactly({ names: ["Alice", "Bob", "Eve"] });
    ```

    The type of `names` in the above example is `readonly ["Alice", "Bob", "Eve"]`. Marking the type parameter as `const` behaves as if you had written `as const` at every use instead. The above code is equivalent to the following TypeScript, which was the only option before TypeScript 5.0:

    ```ts
    type HasNames = { names: readonly string[] };
    const getNamesExactly = <T extends HasNames>(arg: T): T["names"] => arg.names;
    const names = getNamesExactly({ names: ["Alice", "Bob", "Eve"] } as const);
    ```

    You can read [the announcement](https://devblogs.microsoft.com/typescript/announcing-typescript-5-0-beta/#const-type-parameters) for more information.

* Make parsing generic `async` arrow functions more strict in `.tsx` files

    Previously esbuild's TypeScript parser incorrectly accepted the following code as valid:

    ```tsx
    let fn = async <T> () => {};
    ```

    The official TypeScript parser rejects this code because it thinks it's the identifier `async` followed by a JSX element starting with `<T>`. So with this release, esbuild will now reject this syntax in `.tsx` files too. You'll now have to add a comma after the type parameter to get generic arrow functions like this to parse in `.tsx` files:

    ```tsx
    let fn = async <T,> () => {};
    ```

* Allow the `in` and `out` type parameter modifiers on class expressions

    TypeScript 4.7 added the `in` and `out` modifiers on the type parameters of classes, interfaces, and type aliases. However, while TypeScript supported them on both class expressions and class statements, previously esbuild only supported them on class statements due to an oversight. This release now allows these modifiers on class expressions too:

    ```ts
    declare let Foo: any;
    Foo = class <in T> { };
    Foo = class <out T> { };
    ```

* Update `enum` constant folding for TypeScript 5.0

    TypeScript 5.0 contains an [updated definition of what it considers a constant expression](https://github.com/microsoft/TypeScript/pull/50528):

    > An expression is considered a *constant expression* if it is
    >
    > * a number or string literal,
    > * a unary `+`, `-`, or `~` applied to a numeric constant expression,
    > * a binary `+`, `-`, `*`, `/`, `%`, `**`, `<<`, `>>`, `>>>`, `|`, `&`, `^` applied to two numeric constant expressions,
    > * a binary `+` applied to two constant expressions whereof at least one is a string,
    > * a template expression where each substitution expression is a constant expression,
    > * a parenthesized constant expression,
    > * a dotted name (e.g. `x.y.z`) that references a `const` variable with a constant expression initializer and no type annotation,
    > * a dotted name that references an enum member with an enum literal type, or
    > * a dotted name indexed by a string literal (e.g. `x.y["z"]`) that references an enum member with an enum literal type.

    This impacts esbuild's implementation of TypeScript's `const enum` feature. With this release, esbuild will now attempt to follow these new rules. For example, you can now initialize an `enum` member with a template literal expression that contains a numeric constant:

    ```ts
    // Original input
    const enum Example {
      COUNT = 100,
      ERROR = `Expected ${COUNT} items`,
    }
    console.log(
      Example.COUNT,
      Example.ERROR,
    )

    // Old output (with --tree-shaking=true)
    var Example = /* @__PURE__ */ ((Example2) => {
      Example2[Example2["COUNT"] = 100] = "COUNT";
      Example2[Example2["ERROR"] = `Expected ${100 /* COUNT */} items`] = "ERROR";
      return Example2;
    })(Example || {});
    console.log(
      100 /* COUNT */,
      Example.ERROR
    );

    // New output (with --tree-shaking=true)
    console.log(
      100 /* COUNT */,
      "Expected 100 items" /* ERROR */
    );
    ```

    These rules are not followed exactly due to esbuild's limitations. The rule about dotted references to `const` variables is not followed both because esbuild's enum processing is done in an isolated module setting and because doing so would potentially require esbuild to use a type system, which it doesn't have. For example:

    ```ts
    // The TypeScript compiler inlines this but esbuild doesn't:
    declare const x = 'foo'
    const enum Foo { X = x }
    console.log(Foo.X)
    ```

    Also, the rule that requires converting numbers to a string currently only followed for 32-bit signed integers and non-finite numbers. This is done to avoid accidentally introducing a bug if esbuild's number-to-string operation doesn't exactly match the behavior of a real JavaScript VM. Currently esbuild's number-to-string constant folding is conservative for safety.

* Forbid definite assignment assertion operators on class methods

    In TypeScript, class methods can use the `?` optional property operator but not the `!` definite assignment assertion operator (while class fields can use both):

    ```ts
    class Foo {
      // These are valid TypeScript
      a?
      b!
      x?() {}

      // This is invalid TypeScript
      y!() {}
    }
    ```

    Previously esbuild incorrectly allowed the definite assignment assertion operator with class methods. This will no longer be allowed starting with this release.

## 0.17.4

* Implement HTTP `HEAD` requests in serve mode ([#2851](https://github.com/evanw/esbuild/issues/2851))

    Previously esbuild's serve mode only responded to HTTP `GET` requests. With this release, esbuild's serve mode will also respond to HTTP `HEAD` requests, which are just like HTTP `GET` requests except that the body of the response is omitted.

* Permit top-level await in dead code branches ([#2853](https://github.com/evanw/esbuild/issues/2853))

    Adding top-level await to a file has a few consequences with esbuild:

    1. It causes esbuild to assume that the input module format is ESM, since top-level await is only syntactically valid in ESM. That prevents you from using `module` and `exports` for exports and also enables strict mode, which disables certain syntax and changes how function hoisting works (among other things).
    2. This will cause esbuild to fail the build if either top-level await isn't supported by your language target (e.g. it's not supported in ES2021) or if top-level await isn't supported by the chosen output format (e.g. it's not supported with CommonJS).
    3. Doing this will prevent you from using `require()` on this file or on any file that imports this file (even indirectly), since the `require()` function doesn't return a promise and so can't represent top-level await.

    This release relaxes these rules slightly: rules 2 and 3 will now no longer apply when esbuild has identified the code branch as dead code, such as when it's behind an `if (false)` check. This should make it possible to use esbuild to convert code into different output formats that only uses top-level await conditionally. This release does not relax rule 1. Top-level await will still cause esbuild to unconditionally consider the input module format to be ESM, even when the top-level `await` is in a dead code branch. This is necessary because whether the input format is ESM or not affects the whole file, not just the dead code branch.

* Fix entry points where the entire file name is the extension ([#2861](https://github.com/evanw/esbuild/issues/2861))

    Previously if you passed esbuild an entry point where the file extension is the entire file name, esbuild would use the parent directory name to derive the name of the output file. For example, if you passed esbuild a file `./src/.ts` then the output name would be `src.js`. This bug happened because esbuild first strips the file extension to get `./src/` and then joins the path with the working directory to get the absolute path (e.g. `join("/working/dir", "./src/")` gives `/working/dir/src`). However, the join operation also canonicalizes the path which strips the trailing `/`. Later esbuild uses the "base name" operation to extract the name of the output file. Since there is no trailing `/`, esbuild returns `"src"` as the base name instead of `""`, which causes esbuild to incorrectly include the directory name in the output file name. This release fixes this bug by deferring the stripping of the file extension until after all path manipulations have been completed. So now the file `./src/.ts` will generate an output file named `.js`.

* Support replacing property access expressions with inject

    At a high level, this change means the `inject` feature can now replace all of the same kinds of names as the `define` feature. So `inject` is basically now a more powerful version of `define`, instead of previously only being able to do some of the things that `define` could do.

    Soem background is necessary to understand this change if you aren't already familiar with the `inject` feature. The `inject` feature lets you replace references to global variable with a shim. It works like this:

    1. Put the shim in its own file
    2. Export the shim as the name of the global variable you intend to replace
    3. Pass the file to esbuild using the `inject` feature

    For example, if you inject the following file using `--inject:./injected.js`:

    ```js
    // injected.js
    let processShim = { cwd: () => '/' }
    export { processShim as process }
    ```

    Then esbuild will replace all references to `process` with the `processShim` variable, which will cause `process.cwd()` to return `'/'`. This feature is sort of abusing the ESM export alias syntax to specify the mapping of global variables to shims. But esbuild works this way because using this syntax for that purpose is convenient and terse.

    However, if you wanted to replace a property access expression, the process was more complicated and not as nice. You would have to:

    1. Put the shim in its own file
    2. Export the shim as some random name
    3. Pass the file to esbuild using the `inject` feature
    4. Use esbuild's `define` feature to map the property access expression to the random name you made in step 2

    For example, if you inject the following file using `--inject:./injected2.js --define:process.cwd=someRandomName`:

    ```js
    // injected2.js
    let cwdShim = () => '/'
    export { cwdShim as someRandomName }
    ```

    Then esbuild will replace all references to `process.cwd` with the `cwdShim` variable, which will also cause `process.cwd()` to return `'/'` (but which this time will not mess with other references to `process`, which might be desirable).

    With this release, using the inject feature to replace a property access expression is now as simple as using it to replace an identifier. You can now use JavaScript's ["arbitrary module namespace identifier names"](https://github.com/tc39/ecma262/pull/2154) feature to specify the property access expression directly using a string literal. For example, if you inject the following file using `--inject:./injected3.js`:

    ```js
    // injected3.js
    let cwdShim = () => '/'
    export { cwdShim as 'process.cwd' }
    ```

    Then esbuild will now replace all references to `process.cwd` with the `cwdShim` variable, which will also cause `process.cwd()` to return `'/'` (but which will also not mess with other references to `process`).

    In addition to inserting a shim for a global variable that doesn't exist, another use case is replacing references to static methods on global objects with cached versions to both minify them better and to make access to them potentially faster. For example:

    ```js
    // Injected file
    let cachedMin = Math.min
    let cachedMax = Math.max
    export {
      cachedMin as 'Math.min',
      cachedMax as 'Math.max',
    }

    // Original input
    function clampRGB(r, g, b) {
      return {
        r: Math.max(0, Math.min(1, r)),
        g: Math.max(0, Math.min(1, g)),
        b: Math.max(0, Math.min(1, b)),
      }
    }

    // Old output (with --minify)
    function clampRGB(a,t,m){return{r:Math.max(0,Math.min(1,a)),g:Math.max(0,Math.min(1,t)),b:Math.max(0,Math.min(1,m))}}

    // New output (with --minify)
    var a=Math.min,t=Math.max;function clampRGB(h,M,m){return{r:t(0,a(1,h)),g:t(0,a(1,M)),b:t(0,a(1,m))}}
    ```

## 0.17.3

* Fix incorrect CSS minification for certain rules ([#2838](https://github.com/evanw/esbuild/issues/2838))

    Certain rules such as `@media` could previously be minified incorrectly. Due to a typo in the duplicate rule checker, two known `@`-rules that share the same hash code were incorrectly considered to be equal. This problem was made worse by the rule hashing code considering two unknown declarations (such as CSS variables) to have the same hash code, which also isn't optimal from a performance perspective. Both of these issues have been fixed:

    ```css
    /* Original input */
    @media (prefers-color-scheme: dark) { body { --VAR-1: #000; } }
    @media (prefers-color-scheme: dark) { body { --VAR-2: #000; } }

    /* Old output (with --minify) */
    @media (prefers-color-scheme: dark){body{--VAR-2: #000}}

    /* New output (with --minify) */
    @media (prefers-color-scheme: dark){body{--VAR-1: #000}}@media (prefers-color-scheme: dark){body{--VAR-2: #000}}
    ```

## 0.17.2

* Add `onDispose` to the plugin API ([#2140](https://github.com/evanw/esbuild/issues/2140), [#2205](https://github.com/evanw/esbuild/issues/2205))

    If your plugin wants to perform some cleanup after it's no longer going to be used, you can now use the `onDispose` API to register a callback for cleanup-related tasks. For example, if a plugin starts a long-running child process then it may want to terminate that process when the plugin is discarded. Previously there was no way to do this. Here's an example:

    ```js
    let examplePlugin = {
      name: 'example',
      setup(build) {
        build.onDispose(() => {
          console.log('This plugin is no longer used')
        })
      },
    }
    ```

    These `onDispose` callbacks will be called after every `build()` call regardless of whether the build failed or not as well as after the first `dispose()` call on a given build context.

## 0.17.1

* Make it possible to cancel a build ([#2725](https://github.com/evanw/esbuild/issues/2725))

    The context object introduced in version 0.17.0 has a new `cancel()` method. You can use it to cancel a long-running build so that you can start a new one without needing to wait for the previous one to finish. When this happens, the previous build should always have at least one error and have no output files (i.e. it will be a failed build).

    Using it might look something like this:

    * JS:

        ```js
        let ctx = await esbuild.context({
          // ...
        })

        let rebuildWithTimeLimit = timeLimit => {
          let timeout = setTimeout(() => ctx.cancel(), timeLimit)
          return ctx.rebuild().finally(() => clearTimeout(timeout))
        }

        let build = await rebuildWithTimeLimit(500)
        ```

    * Go:

        ```go
        ctx, err := api.Context(api.BuildOptions{
          // ...
        })
        if err != nil {
          return
        }

        rebuildWithTimeLimit := func(timeLimit time.Duration) api.BuildResult {
          t := time.NewTimer(timeLimit)
          go func() {
            <-t.C
            ctx.Cancel()
          }()
          result := ctx.Rebuild()
          t.Stop()
          return result
        }

        build := rebuildWithTimeLimit(500 * time.Millisecond)
        ```

    This API is a quick implementation and isn't maximally efficient, so the build may continue to do some work for a little bit before stopping. For example, I have added stop points between each top-level phase of the bundler and in the main module graph traversal loop, but I haven't added fine-grained stop points within the internals of the linker. How quickly esbuild stops can be improved in future releases. This means you'll want to wait for `cancel()` and/or the previous `rebuild()` to finish (i.e. await the returned promise in JavaScript) before starting a new build, otherwise `rebuild()` will give you the just-canceled build that still hasn't ended yet. Note that `onEnd` callbacks will still be run regardless of whether or not the build was canceled.

* Fix server-sent events without `servedir` ([#2827](https://github.com/evanw/esbuild/issues/2827))

    The server-sent events for live reload were incorrectly using `servedir` to calculate the path to modified output files. This means events couldn't be sent when `servedir` wasn't specified. This release uses the internal output directory (which is always present) instead of `servedir` (which might be omitted), so live reload should now work when `servedir` is not specified.

* Custom entry point output paths now work with the `copy` loader ([#2828](https://github.com/evanw/esbuild/issues/2828))

    Entry points can optionally provide custom output paths to change the path of the generated output file. For example, `esbuild foo=abc.js bar=xyz.js --outdir=out` generates the files `out/foo.js` and `out/bar.js`. However, this previously didn't work when using the `copy` loader due to an oversight. This bug has been fixed. For example, you can now do `esbuild foo=abc.html bar=xyz.html --outdir=out --loader:.html=copy` to generate the files `out/foo.html` and `out/bar.html`.

* The JS API can now take an array of objects ([#2828](https://github.com/evanw/esbuild/issues/2828))

    Previously it was not possible to specify two entry points with the same custom output path using the JS API, although it was possible to do this with the Go API and the CLI. This will not cause a collision if both entry points use different extensions (e.g. if one uses `.js` and the other uses `.css`). You can now pass the JS API an array of objects to work around this API limitation:

    ```js
    // The previous API didn't let you specify duplicate output paths
    let result = await esbuild.build({
      entryPoints: {
        // This object literal contains a duplicate key, so one is ignored
        'dist': 'foo.js',
        'dist': 'bar.css',
      },
    })

    // You can now specify duplicate output paths as an array of objects
    let result = await esbuild.build({
      entryPoints: [
        { in: 'foo.js', out: 'dist' },
        { in: 'bar.css', out: 'dist' },
      ],
    })
    ```

## 0.17.0

**This release deliberately contains backwards-incompatible changes.** To avoid automatically picking up releases like this, you should either be pinning the exact version of `esbuild` in your `package.json` file (recommended) or be using a version range syntax that only accepts patch upgrades such as `^0.16.0` or `~0.16.0`. See npm's documentation about [semver](https://docs.npmjs.com/cli/v6/using-npm/semver/) for more information.

At a high level, the breaking changes in this release fix some long-standing issues with the design of esbuild's incremental, watch, and serve APIs. This release also introduces some exciting new features such as live reloading. In detail:

* Move everything related to incremental builds to a new `context` API ([#1037](https://github.com/evanw/esbuild/issues/1037), [#1606](https://github.com/evanw/esbuild/issues/1606), [#2280](https://github.com/evanw/esbuild/issues/2280), [#2418](https://github.com/evanw/esbuild/issues/2418))

    This change removes the `incremental` and `watch` options as well as the `serve()` method, and introduces a new `context()` method. The context method takes the same arguments as the `build()` method but only validates its arguments and does not do an initial build. Instead, builds can be triggered using the `rebuild()`, `watch()`, and `serve()` methods on the returned context object. The new context API looks like this:

    ```js
    // Create a context for incremental builds
    const context = await esbuild.context({
      entryPoints: ['app.ts'],
      bundle: true,
    })

    // Manually do an incremental build
    const result = await context.rebuild()

    // Enable watch mode
    await context.watch()

    // Enable serve mode
    await context.serve()

    // Dispose of the context
    context.dispose()
    ```

    The switch to the context API solves a major issue with the previous API which is that if the initial build fails, a promise is thrown in JavaScript which prevents you from accessing the returned result object. That prevented you from setting up long-running operations such as watch mode when the initial build contained errors. It also makes tearing down incremental builds simpler as there is now a single way to do it instead of three separate ways.

    In addition, this release also makes some subtle changes to how incremental builds work. Previously every call to `rebuild()` started a new build. If you weren't careful, then builds could actually overlap. This doesn't cause any problems with esbuild itself, but could potentially cause problems with plugins (esbuild doesn't even give you a way to identify which overlapping build a given plugin callback is running on). Overlapping builds also arguably aren't useful, or at least aren't useful enough to justify the confusion and complexity that they bring. With this release, there is now only ever a single active build per context. Calling `rebuild()` before the previous rebuild has finished now "merges" with the existing rebuild instead of starting a new build.

* Allow using `watch` and `serve` together ([#805](https://github.com/evanw/esbuild/issues/805), [#1650](https://github.com/evanw/esbuild/issues/1650), [#2576](https://github.com/evanw/esbuild/issues/2576))

    Previously it was not possible to use watch mode and serve mode together. The rationale was that watch mode is one way of automatically rebuilding your project and serve mode is another (since serve mode automatically rebuilds on every request). However, people want to combine these two features to make "live reloading" where the browser automatically reloads the page when files are changed on the file system.

    This release now allows you to use these two features together. You can only call the `watch()` and `serve()` APIs once each per context, but if you call them together on the same context then esbuild will automatically rebuild both when files on the file system are changed *and* when the server serves a request.

* Support "live reloading" through server-sent events ([#802](https://github.com/evanw/esbuild/issues/802))

    [Server-sent events](https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events/Using_server-sent_events) are a simple way to pass one-directional messages asynchronously from the server to the client. Serve mode now provides a `/esbuild` endpoint with an `change` event that triggers every time esbuild's output changes. So you can now implement simple "live reloading" (i.e. reloading the page when a file is edited and saved) like this:

    ```js
    new EventSource('/esbuild').addEventListener('change', () => location.reload())
    ```

    The event payload is a JSON object with the following shape:

    ```ts
    interface ChangeEvent {
      added: string[]
      removed: string[]
      updated: string[]
    }
    ```

    This JSON should also enable more complex live reloading scenarios. For example, the following code hot-swaps changed CSS `<link>` tags in place without reloading the page (but still reloads when there are other types of changes):

    ```js
    new EventSource('/esbuild').addEventListener('change', e => {
      const { added, removed, updated } = JSON.parse(e.data)
      if (!added.length && !removed.length && updated.length === 1) {
        for (const link of document.getElementsByTagName("link")) {
          const url = new URL(link.href)
          if (url.host === location.host && url.pathname === updated[0]) {
            const next = link.cloneNode()
            next.href = updated[0] + '?' + Math.random().toString(36).slice(2)
            next.onload = () => link.remove()
            link.parentNode.insertBefore(next, link.nextSibling)
            return
          }
        }
      }
      location.reload()
    })
    ```

    Implementing live reloading like this has a few known caveats:

    * These events only trigger when esbuild's output changes. They do not trigger when files unrelated to the build being watched are changed. If your HTML file references other files that esbuild doesn't know about and those files are changed, you can either manually reload the page or you can implement your own live reloading infrastructure instead of using esbuild's built-in behavior.

    * The `EventSource` API is supposed to automatically reconnect for you. However, there's a bug in Firefox that breaks this if the server is ever temporarily unreachable: https://bugzilla.mozilla.org/show_bug.cgi?id=1809332. Workarounds are to use any other browser, to manually reload the page if this happens, or to write more complicated code that manually closes and re-creates the `EventSource` object if there is a connection error. I'm hopeful that this bug will be fixed.

    * Browser vendors have decided to not implement HTTP/2 without TLS. This means that each `/esbuild` event source will take up one of your precious 6 simultaneous per-domain HTTP/1.1 connections. So if you open more than six HTTP tabs that use this live-reloading technique, you will be unable to use live reloading in some of those tabs (and other things will likely also break). The workaround is to enable HTTPS, which is now possible to do in esbuild itself (see below).

* Add built-in support for HTTPS ([#2169](https://github.com/evanw/esbuild/issues/2169))

    You can now tell esbuild's built-in development server to use HTTPS instead of HTTP. This is sometimes necessary because browser vendors have started making modern web features unavailable to HTTP websites. Previously you had to put a proxy in front of esbuild to enable HTTPS since esbuild's development server only supported HTTP. But with this release, you can now enable HTTPS with esbuild without an additional proxy.

    To enable HTTPS with esbuild:

    1. Generate a self-signed certificate. There are many ways to do this. Here's one way, assuming you have `openssl` installed:

        ```
        openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -days 9999 -nodes -subj /CN=127.0.0.1
        ```

    2. Add `--keyfile=key.pem` and `--certfile=cert.pem` to your esbuild development server command
    3. Click past the scary warning in your browser when you load your page

    If you have more complex needs than this, you can still put a proxy in front of esbuild and use that for HTTPS instead. Note that if you see the message "Client sent an HTTP request to an HTTPS server" when you load your page, then you are using the incorrect protocol. Replace `http://` with `https://` in your browser's URL bar.

    Keep in mind that esbuild's HTTPS support has nothing to do with security. The only reason esbuild now supports HTTPS is because browsers have made it impossible to do local development with certain modern web features without jumping through these extra hoops. *Please do not use esbuild's development server for anything that needs to be secure.* It's only intended for local development and no considerations have been made for production environments whatsoever.

* Better support copying `index.html` into the output directory ([#621](https://github.com/evanw/esbuild/issues/621), [#1771](https://github.com/evanw/esbuild/issues/1771))

    Right now esbuild only supports JavaScript and CSS as first-class content types. Previously this meant that if you were building a website with a HTML file, a JavaScript file, and a CSS file, you could use esbuild to build the JavaScript file and the CSS file into the output directory but not to copy the HTML file into the output directory. You needed a separate `cp` command for that.

    Or so I thought. It turns out that the `copy` loader added in version 0.14.44 of esbuild is sufficient to have esbuild copy the HTML file into the output directory as well. You can add something like `index.html --loader:.html=copy` and esbuild will copy `index.html` into the output directory for you. The benefits of this are a) you don't need a separate `cp` command and b) the `index.html` file will automatically be re-copied when esbuild is in watch mode and the contents of `index.html` are edited. This also goes for other non-HTML file types that you might want to copy.

    This pretty much already worked. The one thing that didn't work was that esbuild's built-in development server previously only supported implicitly loading `index.html` (e.g. loading `/about/index.html` when you visit `/about/`) when `index.html` existed on the file system. Previously esbuild didn't support implicitly loading `index.html` if it was a build result. That bug has been fixed with this release so it should now be practical to use the `copy` loader to do this.

* Fix `onEnd` not being called in serve mode ([#1384](https://github.com/evanw/esbuild/issues/1384))

    Previous releases had a bug where plugin `onEnd` callbacks weren't called when using the top-level `serve()` API. This API no longer exists and the internals have been reimplemented such that `onEnd` callbacks should now always be called at the end of every build.

* Incremental builds now write out build results differently ([#2104](https://github.com/evanw/esbuild/issues/2104))

    Previously build results were always written out after every build. However, this could cause the output directory to fill up with files from old builds if code splitting was enabled, since the file names for code splitting chunks contain content hashes and old files were not deleted.

    With this release, incremental builds in esbuild will now delete old output files from previous builds that are no longer relevant. Subsequent incremental builds will also no longer overwrite output files whose contents haven't changed since the previous incremental build.

* The `onRebuild` watch mode callback was removed ([#980](https://github.com/evanw/esbuild/issues/980), [#2499](https://github.com/evanw/esbuild/issues/2499))

    Previously watch mode accepted an `onRebuild` callback which was called whenever watch mode rebuilt something. This was not great in practice because if you are running code after a build, you likely want that code to run after every build, not just after the second and subsequent builds. This release removes option to provide an `onRebuild` callback. You can create a plugin with an `onEnd` callback instead. The `onEnd` plugin API already exists, and is a way to run some code after every build.

* You can now return errors from `onEnd` ([#2625](https://github.com/evanw/esbuild/issues/2625))

    It's now possible to add additional build errors and/or warnings to the current build from within your `onEnd` callback by returning them in an array. This is identical to how the `onStart` callback already works. The evaluation of `onEnd` callbacks have been moved around a bit internally to make this possible.

    Note that the build will only fail (i.e. reject the promise) if the additional errors are returned from `onEnd`. Adding additional errors to the result object that's passed to `onEnd` won't affect esbuild's behavior at all.

* Print URLs and ports from the Go and JS APIs ([#2393](https://github.com/evanw/esbuild/issues/2393))

    Previously esbuild's CLI printed out something like this when serve mode is active:

    ```
     > Local:   http://127.0.0.1:8000/
     > Network: http://192.168.0.1:8000/
    ```

    The CLI still does this, but now the JS and Go serve mode APIs will do this too. This only happens when the log level is set to `verbose`, `debug`, or `info` but not when it's set to `warning`, `error`, or `silent`.

### Upgrade guide for existing code:

* Rebuild (a.k.a. incremental build):

    Before:

    ```js
    const result = await esbuild.build({ ...buildOptions, incremental: true });
    builds.push(result);
    for (let i = 0; i < 4; i++) builds.push(await result.rebuild());
    await result.rebuild.dispose(); // To free resources
    ```

    After:

    ```js
    const ctx = await esbuild.context(buildOptions);
    for (let i = 0; i < 5; i++) builds.push(await ctx.rebuild());
    await ctx.dispose(); // To free resources
    ```

    Previously the first build was done differently than subsequent builds. Now both the first build and subsequent builds are done using the same API.

* Serve:

    Before:

    ```js
    const serveResult = await esbuild.serve(serveOptions, buildOptions);
    ...
    serveResult.stop(); await serveResult.wait; // To free resources
    ```

    After:

    ```js
    const ctx = await esbuild.context(buildOptions);
    const serveResult = await ctx.serve(serveOptions);
    ...
    await ctx.dispose(); // To free resources
    ```

* Watch:

    Before:

    ```js
    const result = await esbuild.build({ ...buildOptions, watch: true });
    ...
    result.stop(); // To free resources
    ```

    After:

    ```js
    const ctx = await esbuild.context(buildOptions);
    await ctx.watch();
    ...
    await ctx.dispose(); // To free resources
    ```

* Watch with `onRebuild`:

    Before:

    ```js
    const onRebuild = (error, result) => {
      if (error) console.log('subsequent build:', error);
      else console.log('subsequent build:', result);
    };
    try {
      const result = await esbuild.build({ ...buildOptions, watch: { onRebuild } });
      console.log('first build:', result);
      ...
      result.stop(); // To free resources
    } catch (error) {
      console.log('first build:', error);
    }
    ```

    After:

    ```js
    const plugins = [{
      name: 'my-plugin',
      setup(build) {
        let count = 0;
        build.onEnd(result => {
          if (count++ === 0) console.log('first build:', result);
          else console.log('subsequent build:', result);
        });
      },
    }];
    const ctx = await esbuild.context({ ...buildOptions, plugins });
    await ctx.watch();
    ...
    await ctx.dispose(); // To free resources
    ```

    The `onRebuild` function has now been removed. The replacement is to make a plugin with an `onEnd` callback.

    Previously `onRebuild` did not fire for the first build (only for subsequent builds). This was usually problematic, so using `onEnd` instead of `onRebuild` is likely less error-prone. But if you need to emulate the old behavior of `onRebuild` that ignores the first build, then you'll need to manually count and ignore the first build in your plugin (as demonstrated above).

Notice how all of these API calls are now done off the new context object. You should now be able to use all three kinds of incremental builds (`rebuild`, `serve`, and `watch`) together on the same context object. Also notice how calling `dispose` on the context is now the common way to discard the context and free resources in all of these situations.

## 0.16.17

* Fix additional comment-related regressions ([#2814](https://github.com/evanw/esbuild/issues/2814))

    This release fixes more edge cases where the new comment preservation behavior that was added in 0.16.14 could introduce syntax errors. Specifically:

    ```js
    x = () => (/* comment */ {})
    for ((/* comment */ let).x of y) ;
    function *f() { yield (/* comment */class {}) }
    ```

    These cases caused esbuild to generate code with a syntax error in version 0.16.14 or above. These bugs have now been fixed.

## 0.16.16

* Fix a regression caused by comment preservation ([#2805](https://github.com/evanw/esbuild/issues/2805))

    The new comment preservation behavior that was added in 0.16.14 introduced a regression where comments in certain locations could cause esbuild to omit certain necessary parentheses in the output. The outermost parentheses were incorrectly removed for the following syntax forms, which then introduced syntax errors:

    ```js
    (/* comment */ { x: 0 }).x;
    (/* comment */ function () { })();
    (/* comment */ class { }).prototype;
    ```

    This regression has been fixed.

## 0.16.15

* Add `format` to input files in the JSON metafile data

    When `--metafile` is enabled, input files may now have an additional `format` field that indicates the export format used by this file. When present, the value will either be `cjs` for CommonJS-style exports or `esm` for ESM-style exports. This can be useful in bundle analysis.

    For example, esbuild's new [Bundle Size Analyzer](https://esbuild.github.io/analyze/) now uses this information to visualize whether ESM or CommonJS was used for each directory and file of source code (click on the CJS/ESM bar at the top).

    This information is helpful when trying to reduce the size of your bundle. Using the ESM variant of a dependency instead of the CommonJS variant always results in a faster and smaller bundle because it omits CommonJS wrappers, and also may result in better tree-shaking as it allows esbuild to perform tree-shaking at the statement level instead of the module level.

* Fix a bundling edge case with dynamic import ([#2793](https://github.com/evanw/esbuild/issues/2793))

    This release fixes a bug where esbuild's bundler could produce incorrect output. The problematic edge case involves the entry point importing itself using a dynamic `import()` expression in an imported file, like this:

    ```js
    // src/a.js
    export const A = 42;

    // src/b.js
    export const B = async () => (await import(".")).A

    // src/index.js
    export * from "./a"
    export * from "./b"
    ```

* Remove new type syntax from type declarations in the `esbuild` package ([#2798](https://github.com/evanw/esbuild/issues/2798))

    Previously you needed to use TypeScript 4.3 or newer when using the `esbuild` package from TypeScript code due to the use of a getter in an interface in `node_modules/esbuild/lib/main.d.ts`. This release removes this newer syntax to allow people with versions of TypeScript as far back as TypeScript 3.5 to use this latest version of the `esbuild` package. Here is change that was made to esbuild's type declarations:

    ```diff
     export interface OutputFile {
       /** "text" as bytes */
       contents: Uint8Array;
       /** "contents" as text (changes automatically with "contents") */
    -  get text(): string;
    +  readonly text: string;
     }
    ```

## 0.16.14

* Preserve some comments in expressions ([#2721](https://github.com/evanw/esbuild/issues/2721))

    Various tools give semantic meaning to comments embedded inside of expressions. For example, Webpack and Vite have special "magic comments" that can be used to affect code splitting behavior:

    ```js
    import(/* webpackChunkName: "foo" */ '../foo');
    import(/* @vite-ignore */ dynamicVar);
    new Worker(/* webpackChunkName: "bar" */ new URL("../bar.ts", import.meta.url));
    new Worker(new URL('./path', import.meta.url), /* @vite-ignore */ dynamicOptions);
    ```

    Since esbuild can be used as a preprocessor for these tools (e.g. to strip TypeScript types), it can be problematic if esbuild doesn't do additional work to try to retain these comments. Previously esbuild special-cased Webpack comments in these specific locations in the AST. But Vite would now like to use similar comments, and likely other tools as well.

    So with this release, esbuild now will attempt to preserve some comments inside of expressions in more situations than before. This behavior is mainly intended to preserve these special "magic comments" that are meant for other tools to consume, although esbuild will no longer only preserve Webpack-specific comments so it should now be tool-agnostic. There is no guarantee that all such comments will be preserved (especially when `--minify-syntax` is enabled). So this change does *not* mean that esbuild is now usable as a code formatter. In particular comment preservation is more likely to happen with leading comments than with trailing comments. You should put comments that you want to be preserved *before* the relevant expression instead of after it. Also note that this change does not retain any more statement-level comments than before (i.e. comments not embedded inside of expressions). Comment preservation is not enabled when `--minify-whitespace` is enabled (which is automatically enabled when you use `--minify`).

## 0.16.13

* Publish a new bundle visualization tool

    While esbuild provides bundle metadata via the `--metafile` flag, previously esbuild left analysis of it completely up to third-party tools (well, outside of the rudimentary `--analyze` flag). However, the esbuild website now has a built-in bundle visualization tool:

    * https://esbuild.github.io/analyze/

    You can pass `--metafile` to esbuild to output bundle metadata, then upload that JSON file to this tool to visualize your bundle. This is helpful for answering questions such as:

    * Which packages are included in my bundle?
    * How did a specific file get included?
    * How small did a specific file compress to?
    * Was a specific file tree-shaken or not?

    I'm publishing this tool because I think esbuild should provide *some* answer to "how do I visualize my bundle" without requiring people to reach for third-party tools. At the moment the tool offers two types of visualizations: a radial "sunburst chart" and a linear "flame chart". They serve slightly different but overlapping use cases (e.g. the sunburst chart is more keyboard-accessible while the flame chart is easier with the mouse). This tool may continue to evolve over time.

* Fix `--metafile` and `--mangle-cache` with `--watch` ([#1357](https://github.com/evanw/esbuild/issues/1357))

    The CLI calls the Go API and then also writes out the metafile and/or mangle cache JSON files if those features are enabled. This extra step is necessary because these files are returned by the Go API as in-memory strings. However, this extra step accidentally didn't happen for all builds after the initial build when watch mode was enabled. This behavior used to work but it was broken in version 0.14.18 by the introduction of the mangle cache feature. This release fixes the combination of these features, so the metafile and mangle cache features should now work with watch mode. This behavior was only broken for the CLI, not for the JS or Go APIs.

* Add an `original` field to the metafile

    The metadata file JSON now has an additional field: each import in an input file now contains the pre-resolved path in the `original` field in addition to the post-resolved path in the `path` field. This means it's now possible to run certain additional analysis over your bundle. For example, you should be able to use this to detect when the same package subpath is represented multiple times in the bundle, either because multiple versions of a package were bundled or because a package is experiencing the [dual-package hazard](https://nodejs.org/api/packages.html#dual-package-hazard).
