Fix CSS nesting transform for triple-nested rules that start with a combinator (#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:

/* 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)

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.

Allow keywords as type parameter names in mapped types (#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:

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, #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:

// 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)

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:

// 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)

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.

Allow the TypeScript 5.0 const modifier in object type declarations (#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:

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

Implement preliminary lowering for CSS nesting (#1945)

Chrome has implemented the new CSS nesting specification 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 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:

/* 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:

/* 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:

/* 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:

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

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

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

Work around an issue with NODE_PATH and Go's WebAssembly internals (#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)

CSS at-rules require either a {} block or a semicolon at the end. 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 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):

/* 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. 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:

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

...would be treated the same as:

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:

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

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

Fix a crash when parsing inline TypeScript decorators (#2991)

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

@(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.

Fix the alias feature to always prefer the longest match (#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)

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

// 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)

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/.

Update esbuild's handling of CSS nesting to match the latest specification changes (#1945)

The syntax for the upcoming CSS nesting feature has recently changed. 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:

.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:

<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)

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:

/* 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)}

Parse rest bindings in TypeScript types (#2937)

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

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)

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:

// 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)

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.

Fix a minification bug with non-ASCII identifiers (#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:

// 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)

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:

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).

Change esbuild's parsing of TypeScript instantiation expressions to match TypeScript 4.8+ (#2907)

This release updates esbuild's implementation of instantiation expression erasure to match microsoft/TypeScript#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, #1458, #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, #2895)

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

// 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
);