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`.a{*zoom:1}` is the IE 6/7 star hack. `RuleBodyParser::next` took only
an identifier as the start of a declaration, so the hack failed the
build with `Unexpected end of input`.
A `*` directly before an identifier now starts a declaration in a style
rule, a keyframe block, `@page`, `@viewport` and a style attribute. It
is stored as an unknown property under its written name
(`CustomPropertyName::StarHack`) and printed as written, like `_zoom`.
`@font-face`, `@property` and `@font-palette-values` do not change.
A style rule that holds a star hack is never taken for a duplicate of
another rule: `PropertyId` equality does not compare the names of
unknown properties.
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Updated 10:33 AM PT - Oct 24th, 2026
✅ @robobun, your commit ee3fa105994dc4cf26d4e55b5d1be99f02148b01 passed in 🧪 To try this PR locally: bunx bun-pr 46751That installs a local version of the PR into your bun-46751 --bun |
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Status
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No actionable comments were generated in the recent review.
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| Layer / File(s) | Summary |
|---|---|
Star-hack representation and value parsing src/css/properties/custom.rs, src/css/css_parser.rs, src/css/declaration.rs |
CustomPropertyName now represents star-hack names and serializes their original bytes. A declaration parsing hook and shared parser store values in the normal or !important declaration list. |
Declaration routing and rule handling src/css/css_parser.rs, src/css/rules/page.rs, src/css/declaration.rs, src/css/rules/style.rs |
RuleBodyParser detects eligible star-prefixed declarations and delegates parsing. The page parser forwards to shared parsing. Duplicate-rule checks exclude rules that contain star-hack declarations. |
Parser and bundler coverage test/js/bun/css/css.test.ts, test/bundler/esbuild/css.test.ts, test/js/bun/css/files/tachyons.css |
Tests cover formatting, declaration contexts, property distinction, CSS Modules composition, URL handling, and malformed syntax. The Tachyons clearfix rule enables *zoom: 1. |
Suggested reviewers: jarred-sumner, alii
Priority:
Merge Risk: 
ee3fa
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The change adds the intended star-hack parsing behavior, with no identified issue requiring correction before merge.
Pre-merge checks: 
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Check name Status Explanation Title check The title clearly and concisely identifies the main change: parsing the CSS *propertyhack as a declaration.Linked Issues check Check skipped because no linked issues were found for this pull request. Out of Scope Changes check Check skipped because no linked issues were found for this pull request. Description check The description is complete and relevant. It explains the problem, fix, behavior changes, limitations, performance impact, and verification steps. It does not use the template headings exactly, but it… Full details: Description check
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Explanation
The description is complete and relevant. It explains the problem, fix, behavior changes, limitations, performance impact, and verification steps. It does not use the template headings exactly, but it provides the required information in equivalent sections.
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Nothing blocking. The comments below are optional suggestions. There is no need to push a fix for them before merging.
Beyond the inline findings, I also checked the &'static [u8] name from slice_from_cloned (it borrows the source text the same way Unknown idents do, so it does not outlive the sheet), the fallback in parse_star_hack_declaration for * at EOF, * zoom, *--x and *zoom:1 !ie (input is reset to just after the * and the item takes the existing error path, so a nested selector starting with * is unaffected), and the !ie case leaving no import record behind since the rejected CustomProperty is dropped before any declaration is pushed. This is a parser behavior change the description itself flags as needing a maintainer decision, so a human look is still worthwhile.
Extended reasoning...
The change adds a *property star-hack path to the CSS rule-body parser, a CustomPropertyName::StarHack variant, overrides in the style, nested, and @ page declaration parsers, and a duplicate-rule guard, with tests in both CSS test files. It touches no security-sensitive surface. Three verified findings are posted inline (pre-existing duplicate-rule loss for other unknown properties, new url() resolution failures in keyframe/page blocks, and hack reordering under minify), and the PR is an explicit behavior change the author says needs a maintainer's decision, so it is not approvable by this review.
| let value = input.parse_until_before( | ||
| css::Delimiters::BANG | css::Delimiters::CURLY_BRACKET, | ||
| |input2: &mut css::Parser| CustomProperty::parse(name, input2, options), | ||
| )?; |
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🟡 (optional) Users bundling a sheet whose keyframe block holds *background: url(./missing.png) now get a failed build where main exits 0. The star-hack value is parsed as a CustomProperty at src/css/declaration.rs:429-432, so every url() in it becomes an import record that the bundler must resolve. On main the * made the declaration an error, the recovering body dropped the block, and the build went on. Legacy sheets whose IE-only assets were pruned are exactly the population this hack appears in. Fix: a url() inside a *property value should not fail the build (resolve it best-effort and keep the raw text, or warn), for keyframes, @ page and style rules alike.
Why this was flagged
Trigger: a stylesheet containing @ keyframes k{from{*background:url(./missing.png)}to{top:2px}} or @ page{*background:url(./missing.png)} passed to bun build. The new path src/css/css_parser.rs:2903-2909 accepts the *ident and calls parse_star_hack at src/css/declaration.rs:421; CustomProperty::parse at src/css/declaration.rs:431 records the url() via add_import_record (src/css/css_parser.rs:3153) and the declaration succeeds, so reset never truncates it. On the base commit the * reaches the else branch at src/css/css_parser.rs:2920 as an unexpected token; the keyframe body drops the block and the build exits 0. After merge the bundler reports Could not resolve: "./missing.png" and the build fails. Population: legacy sheets with star-hacked IE asset paths whose images were removed. Remedy: do not turn a url() in a star-hack value into a hard import, or at least degrade it to a warning like esbuild does.
Verification: Trigger: a star-hack declaration inside a @ keyframes block whose url() names a file that does not exist. src/css/declaration.rs:429-432 parse_star_hack parses the value with CustomProperty::parse, which calls input.add_import_record(...); the bundler treats an unresolvable record as a hard error. On base the keyframes loop at src/css/css_parser.rs:1780-1784 drops the block and exits 0.
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Kept on purpose. A url() in the value of any unknown property is an import on main: _background: url(./missing.png) fails the build in the same way, in a style rule and in a keyframe block. A hack value that kept its url() as text would point at a file that the bundler did not copy, also when the file exists. The description lists the keyframe case as a new failure, and css/StarHackURLMissingFile pins the error. If a maintainer wants a different policy for hack values, it is a change in parse_star_hack only.
| let property = css::Property::Custom(value); | ||
| if important { | ||
| important_declarations.push(property); | ||
| } else { | ||
| declarations.push(property); |
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🟡 (optional) Users minifying .a{width:1px;*width:2px;height:3px} get .a{*width:2px;width:1px;height:3px}: the hack is printed before the property it was written to override, inverting the IE cascade the author of the sheet relied on. The star-hack property is pushed as a plain Custom property at src/css/declaration.rs:436-440, and DeclarationBlock::minify at src/css/declaration.rs:93-101 moves unhandled Custom properties into hndlr.decls immediately while SizeHandler emits width only at finalize (src/css/declaration.rs:114). On main these sheets did not build at all, so no user got silently reordered output. Fix: keep a *prop (and _prop) in source order relative to the property it names, e.g. flush the handler's held property before pushing the hack, as #45825's flush_before_alias does.
Why this was flagged
Trigger: any stylesheet with width:1px;*width:2px (about 1,500 of 3,658 corpus hacks follow the property they name, per the PR) built with minify, through bun build --minify or Bun.CSS. parse_star_hack pushes Property::Custom into declarations at src/css/declaration.rs:440. In minify, handle at src/css/declaration.rs:90-103 calls handle_property; SizeHandler takes width and holds it, while the StarHack Custom property is not handled and is pushed to hndlr.decls at line 101; finalize at line 114 then appends width. Output is *width:2px;width:1px, pinned by test/js/bun/css/css.test.ts:195-196. The base branch rejected the whole sheet with Unexpected end of input, so this output is new for every sheet the PR unlocks (231 of 3,129 npm sheets). The _width precedent the dismissal relies on is the same bug, not a justification. Remedy: preserve relative order between a hack and the property it names (flush the held property before appending the hack, or never reorder unknown properties past handler-held ones).
Verification: A star-hack declaration that follows a property a shorthand handler owns (width:1px;*width:2px) is pushed as Property::Custom at src/css/declaration.rs:436-440 and goes to hndlr.decls at line 99-101, while width is only re-emitted in finalize, so it lands after the hack. For IE 6/7, width:1px wins instead of 2px. The base branch rejects the input outright, so nothing regresses.
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Documented under "Position" in the notes and pinned by a test beside its _width twin. No browser that Bun can target reads either hack, so the order changes nothing for them. A flush for StarHack alone makes *width and _width print in different orders in one rule. A flush for both hacks changes the output of sheets that build today. #45825 adds the flush mechanism (flush_before_alias), so I left the order of unknown properties to that work.
| // `PropertyId` equality takes `*zoom` for `zoom`, and the loops do | ||
| // not pair a normal declaration with an important one. | ||
| && !self.declarations.has_star_hack() | ||
| && !other.declarations.has_star_hack() |
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🟣 pre-existing, not blocking: pre-existing: minified output still drops a whole style rule when an unknown property such as _zoom is re-declared later, because the new guard only exempts *zoom. is_duplicate at src/css/rules/style.rs:465 compares the total declaration count, then zips only the shorter of the normal and important lists, and PropertyId equality ignores custom names, so .a{zoom:1}.b{color:red}.a{_zoom:2!important} still erases .a{zoom:1}. Fix: make is_duplicate compare the normal and important lists separately by length and compare PropertyId::Custom names, which covers *zoom, _zoom and every other unknown property and lets has_star_hack() go.
A small fix can ride a push you are already making; otherwise a short reply is enough.
Why this was flagged
Input .a{zoom:1}.b{color:red}.a{_zoom:2!important} (or any two unknown-property rules on the same selector, one normal and one !important) reaches StyleRuleKeyMap::remove_duplicate at src/css/rules/mod.rs:953 during minify. hash_key at src/css/rules/style.rs:44 hashes only the Custom tag, so both rules land in one bucket. is_duplicate at src/css/rules/style.rs:466 sees total lengths 1 == 1, then at 469-496 takes min(1, 0) and min(0, 1) as loop bounds, compares nothing, and returns true. The earlier rule is removed from the output. The diff adds has_star_hack() at src/css/rules/style.rs:501-502 which exempts only CustomPropertyName::StarHack; _zoom and other Unknown names still take the pre-existing wrong path, so users get the same lost rule the base branch already produces. The author notes #33684 as the follow-up for the name comparison; the normal-vs-important length mismatch is a separate defect that a two-line length check in this function would close for every property kind.
Verification: pre-existing; acknowledged in diff: the guard added at src/css/rules/style.rs:501-502 exempts only CustomPropertyName::StarHack, so every other unknown property (_zoom, etc.) still hits it. Triggering condition: two non-adjacent style rules with identical selectors and the same number of unknown-property declarations. The base branch drops .a{zoom:1} by the identical route for _zoom.
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This is the defect that #33684 fixes at its owner: PropertyId equality compares custom names there, and is_duplicate compares the normal and the important list separately. It exists on main for _zoom and for every other unknown property. This PR does not copy that change. The guard only keeps the new StarHack variant from reaching the defect. When #33684 lands, has_star_hack() and the guard can be deleted.
### What does this PR do? Consolidates the open pull requests on the CSS parser (`src/css`: parsing, minifying, lowering, printing, CSS modules) into one. 179 open pull requests were in scope. Each was judged by one rule: **the output must mean to a browser what the input meant.** Every claim was run through a build of `main`, a build with the change, lightningcss 1.33 and Chromium 156 (CSSOM, computed values, painted pixels for colors and gradients), and counted against 10,116 real stylesheets: the published CSS of about 190 popular npm packages, plus stylesheets from open source repositories. 107 land here, whole or in part, most of them cut down. The source diff is net negative. Of the 10,116, 9,509 are stylesheets that someone ships. The rest are test fixtures of other tools (521), Tailwind v4 source that needs its plugin (59) and SCSS, PostCSS or template source (27). | 9,509 shipped stylesheets | `main` | this branch | |---|---|---| | fail to build | 71 | 35 | | ... of those, valid CSS that Bun rejects | | 0 | | minified output reads differently in Chromium than the input | 552 | 2 | | CSS modules with a name that is referenced but not defined, or exported but not defined | 166 | 0 | | all 10,116 | `main` | this branch | |---|---|---| | fail to build | 192 | 141 | | minified output reads differently in Chromium than the input | 593 | 15 | | build on `main`, fail here | | 0 | | right on `main`, wrong here (minified, and at the default targets) | | 0 | | size of the minified output, no targets | 162.32 MB | 162.47 MB (+0.093%) | | size of the output at the default targets | 224.1 MB | 210.2 MB (-6.2%) | A syntax error is a build error, with one exception: the IE star hack `*zoom: 1` is skipped, because tachyons and handsontable ship it. The 35 shipped stylesheets that fail are invalid CSS: 28 have a selector that Chromium drops (semantic-ui-css, swiper, @ionic/core, Adobe Spectrum, xp.css), 2 an `@import` after other rules, and one each `@supports not X and Y`, a nested `@keyframes`, a stray comma, a selector list in `::slotted()`, `@media screen\0` (govuk-frontend). The 2 that read differently fold a `color-mix()` inside a gradient (see the known gaps). The growth of the minified output is rules and declarations that `main` deleted by mistake: 87 KB of rules, 45 KB of prefixed declarations that only browser targets can rule out. #### Popular CSS that `main` breaks today - normalize.css, modern-normalize, sanitize.css: `font-family: monospace, monospace` is collapsed to `monospace`, which changes the font size from 16px to 13px (#46662). - CKEditor 5, Tabler, Carbon, VitePress, Ionic, PatternFly, Excalidraw: a rule of custom properties is deleted as a "duplicate" of a later rule with the same selector and other custom properties. 37 stylesheets lose 1,681 custom properties (#33684). - Material Components, daisyUI, DocSearch, plyr: a `var()` size loses to its own fallback (#42101). - nextra, daisyUI, CKEditor: declarations written after a nested rule are moved above it (#45462). - antd 4, purecss, govuk-frontend: browser hacks in selector lists start to apply everywhere (#42100). - foundation-sites, flatpickr, 98.css, blueprintjs, scalar, react-datepicker: the build fails on valid CSS (#46756, #38552, #38534). tachyons, handsontable: it fails on the IE star hack (#46751). - nodejs.org, Mantine: a CSS module exports classes that no rule defines, because the `@apply` or `@mixin` in them is moved out of the rule (#46759). - hint.css and 42 more: `z-index: 1000001` and `1000000` become the same number (#46715). - Adobe Spectrum: `--version: 5.0.1` prints as `5.1`. - A quarter of all stylesheets: minified output has a stray space in `align-items: center` (#41993). #### Behavior changes to look at first 1. **`light-dark()` is kept as written at the default browser targets** (#42009). The lowered form `var(--buncss-light, a) var(--buncss-dark, b)` is invalid unless a compiled `color-scheme` covers the element: 184 of the 215 real stylesheets that get it never define the variable, so every browser drops the declaration. The docs section on the polyfill is removed. 2. **`border` is not built from longhands** (#42072): `border-width:0;border-style:solid;border-color:red` stays three declarations, because `border` also resets `border-image`. 305 real stylesheets grow by 30 KB in total; `bootstrap.min.css` by 113 bytes, 5 gzipped. No real stylesheet was found where the old merge shows, so this is the one to drop if size matters more. 14 existing expectations change. 3. **A CSS module no longer exports names that only occur inside `:global(...)`** (#45487). 73 real modules lose 202 export keys, all of them names that no rule has. `import { g }` or `composes: g` of such a name becomes a build error. 4. **Container names and `@counter-style` names stay global in a CSS module** (#45247 by @mikamikasuki). `main` hashes the `@container` name but not `container-name`, so a named query never matches. postcss-modules (Vite, css-loader, Next.js) keeps them global; lightningcss and esbuild hash both. Global keeps a container that is queried from another file or from JS working. 5. **Syntax errors are build errors, also two that `main` lets through**: a media query that stops short (`@media screen and {`, `@media not {`, `@import "a.css" screen and;`) and `@media (width <) foo {`. No stylesheet of the 10,116 has either. A condition that is valid by the grammar though no browser knows it, `( ... )` or `fn( ... )`, is kept as written (#46756): `(min-width:0\0)`, `(not(hover))`. 6. **Declarations after a nested rule stay where they were written**, as a nested declarations rule (#45462). Changes the output of 199 real stylesheets; in a fuzz of 2,850 nested programs compared by computed style, `main` was wrong in 1,056 and the pull request's code, before it was trimmed here, in none. 7. **`Bun.color`**: `color()` inputs are converted instead of returned as a string (`Bun.color("color(srgb 1 0 0)", "hex")` was `"color(srgb 1 0 0)"`); `currentColor`, system colors and `light-dark()` give `null` in the converting formats instead of the keyword as a string; a relative color or `color-mix()` outside sRGB is clipped, not gamut-mapped (`hsl(from oklch(100% .399 336.3) h s l)` is `#ff5bff`, was `#fff`). 8. The `:-moz-any()` and `:-webkit-any()` copies of rules with `:is()` are gone at the default targets (#45945, #42029). The `:-webkit-any()` copy outranked the original rule: `.title{color:blue} :is(h1,h2,h3){color:red}` painted red. 5.8% of all default-target output was the `:-moz-any()` copies. 9. `Property` grows from 216 to 224 bytes: `Url` stores its text as a slice so that two `url()` values can be compared (#46895). The pull request packed a pointer and a `u32` behind `unsafe` to avoid that. #### Not in this PR, needs a decision - **Raise the default browser targets (#40369) and add a `cssTarget` option (#40368).** Today: Chrome 80, Edge 80, Firefox 78, Safari 14, Opera 67, and no public way to change them. At Vite 8's floor the output of the 9,924 stylesheets is 15.3% smaller (3.9% gzipped). About a dozen fixes here only matter at today's floor, and code for older targets is unreachable without the option. - Vendor prefixes for `user-select`, `appearance`, `hyphens` and five more (#45814): 1,116 real stylesheets lack a prefix they need at the default targets. And for `backdrop-filter` (#44648): 173. - Clip instead of gamut-map in the sRGB fallback of a plain wide-gamut color: deletes about 90 lines, changes every pinned fallback hex. If the mapping stays, #44647 by @oddharsh makes it closer to what browsers paint (colors off by 2/255 or more: 168 to 110 of 3,170 real ones). #### Changes **Rules: duplicates, merging, nesting, fallbacks** - The `:-moz-any()` copy of every rule with `:is()` or `:not(a, b)` is gone: Firefox 78 has `:is()` (#45945). 1,164 real stylesheets - Keep declarations written after a nested rule in place with a nested declarations rule (#45462). 379 real stylesheets - With nesting compiled away, an unknown at-rule inside a style rule was moved out of it: `.wrapper{@apply flex}` printed a bare `@apply flex;` and the rule was gone, so a CSS module exported a class that no rule defines. It now stays in a block under the compiled selector. 72 real modules with Tailwind's `@apply`, 25 with Mantine's `@mixin` (#46759). 316 real stylesheets - Keep !important in the rules generated for logical properties and color-scheme (#38597). 311 real stylesheets - With browser targets, remove an earlier duplicate rule only when its declaration block is equal (#46861). 171 real stylesheets - Compare custom property names in `PropertyId` equality and importance in duplicate-rule detection (#33684). 40 real stylesheets - Keep same-condition @supports rules and empty named @layer blocks (#46733). 31 real stylesheets - Keep target-added vendor prefix passes on cloned and re-minified rules, and never print a bare `:full-screen` (#43339). 12 real stylesheets - Keep the selectors on rules added for color fallbacks and logical properties (#43240). 3 real stylesheets - A later declaration of a property drops the `@supports` color copies of the earlier one, which printed after the rule and won (#45560). 2 real stylesheets - Do not merge style rules in a stylesheet that holds `revert-rule` (#46953). 1 real stylesheets - `@import ... supports(-webkit-mask: none)` kept its prefix (#38589) **Properties and shorthands** - Print align-items:center without a stray space when no safe/unsafe keyword is given (#41993). 3,317 real stylesheets - Emit the physical longhands instead of the inset shorthand for targets without it (#38583). 1,452 real stylesheets - Keep the stops of an upward gradient as written, and drop a `50%` hint only at the midpoint (#46790). 104 real stylesheets - Emit unparsed border-block-* declarations when compiling logical borders (#38582). 89 real stylesheets - Keep repeated font families and dedupe only the inserted system-ui fallbacks (#46662). 88 real stylesheets - A `width` / `height` / `min-*` / `max-*` with `var()` or `env()` was printed before the plain fallback written above it, so the fallback won (#42101). 26 real stylesheets - Keep box-orient and box-direction when flex-direction or flex-flow follows (#45672). 16 real stylesheets - Write held prefixed background declarations at every flush (#46882). 6 real stylesheets - Derive equality for Size2D and BorderRadius, and keep every prefix in the border-radius handler (#45665). 2 real stylesheets - Print `none` instead of an empty border-image, mask-border or mask-box-image value (#45143). 2 real stylesheets - Keep font/transition sub-properties on the side of the shorthand they were written on (#41990). 2 real stylesheets - CSS-wide keywords are not names: `font:12px Arial;font-family:inherit` printed `font:12px inherit`, `color-scheme:inherit` and `color-scheme:auto` printed `normal`, `transition-property:unset` was folded into `transition` (#42022). 2 real stylesheets - Only fold font longhands into `font` when the rule declared a `font` (#45459) - Keep a font family name quoted when its identifiers do not read back as the same name (#46606) - Stop rewriting valid positions into ones browsers reject (#45197) - `border` is no longer built from longhands unless the rule also sets what `border` resets (`border-image`), and an author's `border-image` reset is no longer dropped. `transition` is likewise only written where the rule wrote one, because it resets `transition-behavior` (#42072) - `border; border-image: <gradient>; border-image-slice: 1` lost the gradient in every default build (#42018) - A prefixed `linear-gradient` keeps its direction, written or generated: the prefixed syntax names the starting side and measures angles differently (#46697) **At-rules** - Print @font-face format() keywords as strings (#37979). 439 real stylesheets - Print @supports `not` conditions without a leading space (#38559). 88 real stylesheets - Reset after the number token of a unicode-range (#45835). 33 real stylesheets - Keep `<general-enclosed>` media and container conditions as written (#46756). 24 real stylesheets - A strict range such as `(width < 768px)` lowered for old targets still matched at exactly 768px. The step is now `.02px`. The `not all and` form for other units is not taken (#46806). 18 real stylesheets - Keep scanning an @supports condition after a nested block (#38552). 9 real stylesheets - Every `@counter-style name` printed as `@counter-stylename`, which browsers drop (also #46692). In a CSS module the name now stays global, like the `list-style` that refers to it (#33679). 9 real stylesheets - Keep a keyframe whose block has an invalid item (#46288). 2 real stylesheets - Read an @Property initial-value on the stylesheet's parser, keep an unmatched value as written (#45806). 2 real stylesheets - `@media {}` is `all`. A media query that stops after `and`, `or` or `not` (`@media screen and {`) is a build error; `main` printed `not all` or dropped the condition, silently. The `@layer` and type selector parts are not taken (#46869). 2 real stylesheets - Accept a name-only `@container` and a `style()` feature with no value (#46689). 1 real stylesheets - Parse `<timeline-range-name> <percentage>` keyframe selectors (#45652) - Allow `or` inside parentheses after a media type (#45088) - Print the `=` comparison in media and container queries as `=` (#45071) - Parse the @font-palette-values font-family descriptor as a list of family names (#45484) **Selectors** - Never wrap a selector list in :is() (#46787). 414 real stylesheets - Stop emitting :-webkit-any() copies of :is() that outrank the original rule (#42029). 373 real stylesheets - With browser targets, a selector list with a vendor-prefixed member was split, which revives hacks that rely on other engines dropping the whole list: `.s *::-ms-backdrop,.s{flex:auto}` applied everywhere. Rewritten; the list is printed as written (#42100). 42 real stylesheets - Print the vendor prefix on downleveled :any-link, :read-only, :read-write, :placeholder-shown and :autofill (#42131). 12 real stylesheets - Fix nesting lowering of a `&` that does not lead its selector (#43047). 8 real stylesheets - `@scope`: `&` and implicit selectors compile to `:where(:scope)`, relative selectors and bare declarations parse (#43165). 7 real stylesheets - Only reject bare :global / :local pseudo-classes in CSS modules (#38534). 5 real stylesheets - Stop truncating `@scope to (...)` and stop replacing `&` in the scope-end selector (#43146). 2 real stylesheets - `[xl|href$=".pdf"]` lost its namespace prefix (#45159). 2 real stylesheets - Match An+B keywords exactly and take only `+` as the leading sign (#42953). 1 real stylesheets - Parse ::details-content and ::picker() like ::part() (#45504). 1 real stylesheets - Parse :window-inactive as an ordinary pseudo-class, and accept it after ::selection (#45815) - Print :nth-col(1) and :nth-last-col(1) in functional form (#41575) - `li::before::marker` failed the build (#45810) - `&` inside `:nth-child(... of S)` is resolved when nesting is compiled away. The second selector serializer (326 lines) is deleted (#43024) **Colors and `Bun.color`** - Keep light-dark() as written under the default browser targets (#42009). 227 real stylesheets - Number and percentage channels parse in `lab()`, `lch()`, `oklab()`, `oklch()`, `hsl()` and `hwb()`; the hue of `lch` / `oklch` is no longer scaled by alpha (#45084). 130 real stylesheets - `Bun.color` returns `null` for `currentColor`, system colors and `light-dark()` in the converting formats, instead of the CSS keyword as a string (#33047). 130 real stylesheets - Relative colors: channel keywords are on the scale of their function (`rgb(from #369 calc(r + 10) g b)`), the origin's alpha is kept, a relative color kept as written gets no `@supports` copies, and a result outside sRGB is not folded (#45362). 31 real stylesheets - Keep rotate: 0deg out of none, and keep the origin alpha in relative colors (#38486). 13 real stylesheets - Compute the D50 reference white in f32 so greys convert to lab(l 0 0) like lightningcss (#38535). 7 real stylesheets - Return a missing hue for a grey from conversions into lch, oklch, hsl and hwb (#45201). 5 real stylesheets - Fix color(a98-rgb), srgb-linear relative colors and color-mix(in xyz-d50) (#38487). 4 real stylesheets - Match named colors without regard to ASCII case (#45092). 3 real stylesheets - Fold min(), max() and clamp() over plain numbers (#39515) - `calc(l - .08)` in a percentage channel of a relative color became NaN and printed `#000` (also #45970) (#45971) - Bun.color: convert color() inputs instead of returning them as a CSS string (#38488) - A `color-mix(in srgb, ...)` result outside sRGB prints `color(srgb ...)` instead of a gamut-mapped hex (#39269) **`calc()` and numbers** - Rounding to 6 significant digits ate into the integer part: `z-index:2147483647` became `2147480000`, `max-width:9999999px` became `10000000px`, `--x:1234567.5` became `1234570`. It now only cuts a fraction short: a value kept as tokens prints its source text, a typed value prints every integer digit and at least one digit of the fraction (#46715). 43 real stylesheets - A number without a unit is no longer repaired into `px` (`height:1.5715` is dropped by a standards-mode browser, so it prints as written), `calc(-1 * 0)` is not a length, and on a property of the range [0,∞] (sizes, border radii, padding, border and outline widths, gap, `flex-basis`, `font-size`) a `calc()` that folds below zero prints `0` instead of an invalid negative literal, and a negative literal no longer replaces the valid declaration before it (`width:10px;width:-5px` printed `width:-5px`) (#42104). 24 real stylesheets - Print numbers from the f32's shortest digits, not its f64 expansion (#38565). 17 real stylesheets - Print negative numbers below 1 with a single minus sign (#38516) - Keep math functions over two different length units as written (#38489) - Fold rem() with a truncated quotient, so it keeps the sign of the dividend (#32286) - A one-argument `min()` / `max()` around a sum printed without any function (`width:100% - 20px`) (#46145) - `round()` breaks ties upward and handles a negative step as browsers do (#45249) **CSS modules** - A CSS module exports its `@keyframes` names (`styles.spin`). Hashing is unchanged (#46720). 145 real stylesheets - A name inside `:global(...)` prints plain but was exported as `name_<hash>`, a class no rule has (also #38573) (#45487). 90 real stylesheets - Keep container names global in CSS modules (#45247). 6 real stylesheets - Tag the keyframes name when an `animation` value falls back to raw tokens (#46034). 6 real stylesheets - In a plain stylesheet `composes: a from "./b.css"` was treated as an import: the file was inlined and an absolute path printed (#45961). 4 real stylesheets - Drop a rejected composes instead of failing the file at print time (#38538). 1 real stylesheets - Keep every rule's custom properties for the composes conflict check (#38523) - Keep composes working after a nested rule in the same block (#38520) - `IdentOrRef::hash` read 2 of 16 bytes, so in release builds every class of a module hashed alike (#30784) **Tokens, `url()`, diagnostics** - The block skip stack no longer allocates on every block exit (#39533) - Report the diagnostic's line without its line breaks in position.lineText (#38342). 192 real stylesheets - Compare `url()` values by their text (#46895). 26 real stylesheets - Values kept as tokens keep the blanks they were written with instead of having them re-invented at print time: `attr(x type(<number>))` printed `type(< number> )`, which browsers drop. Minified output still drops the blanks that cannot matter (#45577). 19 real stylesheets - The IE star hack (`*zoom:1`) failed the whole build. The declaration is skipped, as every browser does. It is the one syntax error that builds: tachyons, handsontable and jasmine ship it (#46751). 8 real stylesheets - The path of a copied asset spliced into `url()` is always quoted, so a file name with a space or a parenthesis cannot end the `url()` (#41557). 7 real stylesheets - Move the skip loop of parse_until_before out of the generic body (#39520) - Remove dead code from bun_css: the unused `impl Default for Property` (#45618) - Default the at-rule and qualified-rule parser traits, drop the url_to_css shim (#31999) **Speed** Four inputs that took quadratic or exponential time, or produced output out of proportion, are now linear, with no new limit and no extra pass (#31639, #42243, #38531, #43421). **Tests only** - `css-fuzz.test.ts` never ran in CI and timed out on debug builds; it is a deterministic table now (#38500) - `nth-anplusb-ident.test.ts` counts heaps in a child process (#46331) - `color.test.ts` checks the ansi-16 sweep with one `expect()` (#42824) - Not CSS, but it failed this PR's CI and fails on `main` too: `ws-proxy.test.ts` on Windows, "a message sent during a TLS renegotiation arrives after it". The helper server now renegotiates from the callback of the frame's write (#46170) **No pull request covered these** - `--v: 5.0.1` printed as `5.1`, `--w: 1.0.0` as `10`, `--x: 1+2` as `12`, `2n+1` as `2n1`: a number token that touches another keeps its source text. - `color-scheme: auto` printed as `normal`, and `color-scheme: dark light` as `light dark`. - A bare `:global` or `:local` in a CSS module sets the scope of the names after it, up to the end of the selector, as in css-loader. It was a build error. - The scrollbar states (`a:horizontal`, `::-webkit-scrollbar{&:horizontal{}}`) are valid in a plain compound, as in WebKit and Blink. - Without browser targets, `-webkit-box-align`, `-ms-flex-align` and the like were dropped next to their standard form (flatpickr, foundation-sites, materialize-css: 28 stylesheets), and `-webkit-fill-available` before `-moz-available` (beercss). - `(-o-min-device-pixel-ratio: 2/1)` printed as `2`. - `sin()`, `cos()` and `tan()` are exact at multiples of 90deg: `calc(100px * cos(90deg))` printed `-.00000437114px`. - A `display-p3` color at targets that have P3 but not the other `color()` spaces (Safari 10.1 to 14) got itself as a fallback. - `width: rem(-18px, 5px)` folds to a negative literal once `rem()` is right; it prints `0`. - Consecutive nested declarations rules, which arise when same-query `@media` blocks in one rule merge, are folded into one and count against the existing selector expansion limit as the `&{}` rules they replace did. #### Known and not fixed here - Four longhands are still folded into a `transition` the author did not write where the targets add a prefixed copy of a property (`mask-image` at Chrome 80): only the shorthand gives the copy its own times. - A later `background`, `box-shadow` or `border-*` declaration still loses to the `@supports` copy of an earlier `var()` value of the same property with a wide-gamut color. Same on `main`; #45560 is taken for the properties of the fallback handler and for unparsed values only. - A merged rule prints the unprefixed name in the passes of the rule it absorbed: `.d::-webkit-input-placeholder{}.d::-moz-placeholder{}` prints `::placeholder` for the second (#42106, not taken: it breaks the merge of prefix-equivalent rules). - The `border`, `outline` and `font` shorthands, `line-height`, `scroll-padding`, `background-size` and a few more still print a `calc()` that folds below zero as a negative literal. No real stylesheet has one. - `all` is not a property Bun knows, so `a{margin-top:1px;all:unset}` prints `all` first. Same on `main`. - A selector kept as raw tokens loses the blank before `*` when minified: `--sel: .dark *` prints `.dark*`. Same on `main`. - `width:calc(0% + 12px)` folds to `12px`, which lays out differently in a table cell. Same on `main`. - The `:dir()` / `:lang()` rules of a lowered logical property print before the nested rules of their rule, so a logical declaration written after a nested rule of equal specificity still loses to it. Same on `main`. - A fraction is still rounded to 6 significant digits (`12345.678` prints `12345.7`, `33.3333333333%` prints `33.3333%`). Keeping every digit would add up to 282 KB over the corpus. - `@keyframes "quoted"` is hashed in a module but not exported. - In a module, a keyframes name inside a `var()` fallback is not hashed: `animation: var(--enter, fade 1s)`. Same on `main`. - A `color-mix()` or relative color folded to a hex inside a gradient changes the interpolation from Oklab to sRGB (VS Code, clawhub). Printing `color(srgb ..)` instead needs a fallback for `mask-image`, `list-style-image` and custom properties at the default targets, which have none. - A comma list in `@container` still fails the build. - After a bare `:global`, names that are hashed at print time (`::view-transition-old(foo)`) are still hashed; inside `:global(...)` they are not. #### Pull requests in scope that do not land here - Duplicates of a pull request that lands here: #36961 (of #37979), #38478 (of #46662), #38480 (of #46733), #38482 (of #46715), #38491 (of #38500), #38508 (of #45201), #38513 (of #45362), #38573 (of #45487), #38640 (of #38500), #45525 (of #45247), #45589 (of #46756), #45970 (of #45971) - Already fixed on `main`: #38674 - Right, but for input nobody writes (0 of 10,116 stylesheets, and not new syntax): #31916, #38526, #38592, #39349, #41139, #41801, #42042, #42484, #43078, #45604, #45908, #46086, #46221, #46224, #46273, #46694, #46707, #46737, #46755, #46816, #46870, #46934 - Right or harmless, but not worth their code, their bigger output or the behavior they change: #30905, #31924, #33332, #34426, #36225, #38006, #38512, #38547, #38551, #38561, #38572, #38576, #38607, #38623, #38667, #38692, #42106, #42912, #42918, #43407, #43434, #44700, #45442, #45546, #45747, #45759, #45825, #45946, #46061, #46127, #46206 - Need a decision (see above), stay open: #40368, #40369, #44647, #44648, #45814 - Stays open: #45787 Out of scope: CSS linking and chunking in the bundler, the dev server, docs-only pull requests, and repository-wide sweeps that touch `src/css` in passing. Thanks to @mikamikasuki (#45247), @alii (#39520, #31999) and @oddharsh, whose measurements on #40369 and #41990 were used. Fixes #16727. Fixes #24770. Fixes #30772. Fixes #44704. Fixes #45089. Fixes #45237. Fixes #46872. ### How did you verify your code works? - The 35 CSS test files pass on a debug build, also with `FORCE_COLOR=1`. 600+ of the tests in this branch fail on a build of `main`. An earlier head of this branch passed all 179 CI jobs that ran. - The reproduction of each issue listed above was run on `main` (wrong) and on this branch (right). - Differential run over the 10,116 stylesheets, `main` against this branch, minified without targets and through `Bun.build` at the default targets: no stylesheet that builds on `main` fails; Chromium 156 compares the output with the input rule by rule (CSSOM, then computed values on a sized element in a standards-mode document, colors as painted pixels in sRGB and P3). The comparison has 195 control pairs that must read equal or different. For stylesheets that read differently on both builds, mostly because of lowering, the sets of differences were compared; the three new ones are two minifier fixtures that are wrong on both and one comparison artifact. - CSS modules are checked for consistency instead, since hashed names defeat the comparison: every reference points at a name the output defines, every export exists. - `Bun.color`: 59 inputs in 13 formats on both builds; every changed cell was read.
Problem
bun buildfails on a stylesheet that holds the IE 6/7 star hack..clearfix{*zoom:1}giveserror: Unexpected end of input. 231 of 3,129 npm stylesheets fail on this alone.RuleBodyParser::next(src/css/css_parser.rs:2820) takes only an identifier as the start of a declaration. That is the strict mode of lightningcss, which Bun ported.Fix
*directly before an identifier starts a declaration. It is stored as an unknown property under its written name (CustomPropertyName::StarHack), like_zoom.* zoom:1,*zoom 1and*zoom:1 !iestay errors. Error recovery stays off.*zoomcannot replacezoom.test/js/bun/css/css.test.ts(23 tests fail without the fix),test/bundler/esbuild/css.test.ts(5),doesnt_crash.test.ts(4). Self-reviewed: 13 concerns raised, 11 addressed. Rejected: a flush that keeps*widthafterwidth(_widthwould then differ), and a#zoomarm (one package).Background
*property: value. IE 6 and 7 read it asproperty. Other browsers drop the declaration..clearfix { *zoom: 1 }as its example of CSS thatBun.buildrejects.!ieand drops text without a message.Downsides
.text.*before a property name is no longer an error.url()in the value is an import, as in_background. A missing file fails the build.Notes
Decision needed. lightningcss rejects the hack in its strict mode. Its answer to parcel-bundler/lightningcss#39 was the opt-in
errorRecovery, which drops the declaration and warns. #44833 pins the strict behaviour for the bundler:test/js/bun/css/css-loader.test.tsthere expectsUnexpected token: ;for.clearfix { *zoom: 1; color: red }andUnexpected end of inputfor.a { composes: base; *zoom: 1 }. If this PR lands, those two rows need another invalid input, for examplecolor: blue !ie. #46288 has one keyframe row with*zoomthat flips the same way. esbuild keeps the hack and prints a warning. This PR keeps it with no warning, as_zoomis kept today.Where the hack is taken. Style rules and nested rules, keyframe blocks,
@pageand its margin rules,@viewport, and a style attribute.@font-face,@propertyand@font-palette-valuesdo not change:@font-face{*src:url(a.woff)}drops the item as before.Inputs that change from an error to a build. Every
*ident: valuedeclaration in the blocks above. Still errors, with the same message and position as before:* zoom:1(space),*--x:1,*zoom 1,*zoom:1{..},*zoom:1 !ie, a*zoomat the top level or directly in@media.Position. An unknown property is printed ahead of a property that a shorthand handler holds.
.a{width:1px;*width:2px;height:3px}prints.a{*width:2px;width:1px;height:3px}, and_widthdoes the same on main. A test pins both. In the corpus about 1,500 of the 3,658 star hacks follow the property they name and are printed ahead of it. No browser that Bun targets reads either hack. #45825 addsflush_before_alias, which prints a legacy alias after the declarations it can override. The same flush could keep a hack in place, for_widthand*widthalike.Duplicate rules.
PropertyIdequality compares tag and prefix only, so every unknown property equals every other, andStyleRule::is_duplicatedoes not pair a normal declaration with an important one. Without a guard.a{zoom:1}.b{color:red}.a{*zoom:2!important}loses the first rule. The guard is blunt: a rule with a star hack is never a duplicate, so.a{*zoom:1}.b{}.a{*zoom:1}keeps both rules. #33684 fixes the comparison atPropertyId. When it lands, the guard inrules/style.rscan go.url()in the value. It is resolved like anyurl()in an unknown property.@keyframes k{from{*background:url(./missing.png)}to{top:2px}}is a new failure: main drops thefromblock and exits 0, this PR reportsCould not resolve. A value that is not kept (*background:url(./missing.png) !ie) leaves no import behind (css/StarHackDiscardedURL).Not in this PR.
@media (min-width:0\0)and other unknown media or container conditions: css: keep<general-enclosed>media and container conditions as written #46756. 10 more corpus sheets (flatpickr, foundation-sites) fail on that.#zoom: 1, the hash form of the hack: 32 declarations in 11 sheets of one package (dijit). A#id:hover{}nested rule starts with the same token.color: blue !ie.Measurements. Release builds of this diff and of its base, x64 Linux. valgrind, perf and bloaty are not available in the build container, so the counts come from
perf_event_open(user-space instructions of the whole process) andsize -A.@media: +0.13% (+11.9 per rule).RuleBodyParser::next: two jumps, two alignment nops and one register move per declaration, plus the*compare for an item that does not start with an identifier. The first-token dispatch keeps its bit test. Indirect jumps 1 to 1, indirect calls 4 to 4, 5,828 to 5,939 bytes..text82,231,705 to 82,237,081 bytes,.rodataunchanged. All 18 changed symbols are inbun_css._zoomdeclarations and 10,000*zoomdeclarations both take 20,050 per parse. 200 sheets without the hack take 135,712 per pass with and without the parser change.--minify: 231 sheets newly build (30 packages), 0 newly fail, 0 of the 2,854 others change output, 44 still fail.Tests.
test/js/bun/css/css.test.ts(newstar hackblock),test/bundler/esbuild/css.test.ts(css/StarHack,css/StarHackMinified,css/StarHackIsNotThePropertyItNames,css/StarHackURL,css/StarHackURLMissingFile,css/StarHackDiscardedURL,css/InvalidCSSIsStillAnError), and the.cf { *zoom: 1; }line of the tachyons fixture that #14832 commented out. Also run: the other 17 files oftest/js/bun/css/andtest/bundler/css/css-modules.test.ts.css-fuzz.test.tsandnested-selector-expansion.test.tstime out on a debug build with and without this change.