v0.18.20

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• Support advanced CSS @import rules (#​953, #​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:

  @​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. 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).

v0.18.19

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• Implement composes from CSS modules (#​20)

  This release implements the composes annotation from the CSS modules specification. 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:

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

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

  /* 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:

  (() => {
    // style.css
    var submit = "anim_pulse style_button style_submit";
  
    // app.js
    var div = document.createElement("div");
    div.className = submit;
    document.body.appendChild(div);
  })();

  /* 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 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 (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)

  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, #​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) 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)

  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:

  /* 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 which is probably a good representation of how people expect this feature to work.

v0.18.18

• Fix asset references with the --line-limit flag (#​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)

  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:

  @​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):

  @​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:

  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)

  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:

  /* 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;
  }

v0.18.17

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• 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 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)

  /* 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)

  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:

  /* 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, 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)

  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:

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

  // 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:

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

  // styles.ts
  export interface Button {}