Fix TypeScript-specific class transform edge case (#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:

// 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)

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:

// 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)

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:

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

Provide the stop() API in node to exit esbuild's child process (#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. This release adds it back due to a user request.

Add support for transforming new CSS gradient syntax for older browsers

The specification called CSS Images Module Level 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.

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:

/* 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:

/* 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.

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.

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:

/* 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)

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:

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

This fix was contributed by @magic-akari.

Fix a regression in 0.19.0 regarding paths in tsconfig.json (#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)

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:

/* 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)

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)

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)

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)

Using require() on a file that contains 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.

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:

.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)

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)

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)

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

/* 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.