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…rigin and mask-position as <position> The three rows of the property table used the keyword enum of the `position` property, so a real value never parsed. - transform-origin has a `TransformOrigin` type: an x and a y component that take no side offset, and a z length. It follows Stylo's type. - perspective-origin and mask-position use the x/y `Position`. `Position::parse` is now the `<position>` grammar (one, two or four components). `Position::parse_bg_position` keeps the three-component form for background-position, the mask shorthand and gradients. - The table no longer imports the `position` property module under a short name, so `position::Position` does not resolve there.
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Status Reproduced on bun 1.4.3 and on the #45197 branch with
With this branch they print PR: #46206 |
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Updated 5:07 PM PT - Oct 21st, 2026
❌ @robobun, your commit 6035d67 has 1 failures in
🧪 To try this PR locally: bunx bun-pr 46206That installs a local version of the PR into your bun-46206 --bun |
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Beyond the inline findings, I also checked whether the stricter Position::parse reaches any property other than perspective-origin and mask-position: it is only invoked through the Parse trait registration in src/css/properties/mod.rs, and every other caller (background-position, the background and mask shorthands, the gradient at clause) was moved to parse_bg_position explicitly, so no other property silently got stricter. The -webkit-mask-position three-value gap and the mask shorthand vs mask-position longhand typing difference were also looked at and judged intentional per the PR's own Stylo-based scoping.
Extended reasoning...
The change replaces the mistyped position keyword enum on three property-table rows with a new TransformOrigin value type and a stricter <position> parser, touching the Rust CSS parser only, with no security-sensitive surface. Inline findings already flag the math-function and unitless-number regressions and the gradient at leniency, so a human look is warranted; the note records that the strict Position::parse does not leak into other properties.
Findings marked 🟡 are optional suggestions and need no follow-up push.
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| fn parse_at_position(input: &mut Parser) -> Result<Position> { | ||
| input.expect_ident_matching(b"at")?; | ||
| Position::parse_bg_position(input) |
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🟣 pre-existing, not blocking: Authors who write an invalid three-value at position in a radial or conic gradient get a valid gradient after bundling, so a background the browser would drop starts rendering. parse_at_position at src/css/values/gradient.rs:463-465 calls Position::parse_bg_position, which accepts at left top 10px and Position::to_css prints it as at 0 10px. The spec grammar for at is <position>; the PR added the strict Position::parse for exactly this grammar but did not use it here. Fix: route the gradient at clause through Position::parse (the strict parser) so three-value forms stay as written, matching perspective-origin and mask-position.
A small fix can ride a push you are already making; otherwise a short reply is enough.
Why this was flagged
Input .foo{background:radial-gradient(circle at LEFT TOP 10px,red,blue)} arrives through Image::parse into RadialGradient::parse at src/css/values/gradient.rs:485 and ConicGradient::parse at :579, both calling parse_at_position (src/css/values/gradient.rs:463). parse_bg_position (src/css/values/position.rs:34) returns x=Side(left,None), y=Side(top,10px), and Position::to_css prints 0 10px. The browser rejects the input but accepts the output, so a rule that was ignored before bundling now applies. The PR's own test.todo rows at test/js/bun/css/css.test.ts:7760-7769 state the expected output is the input unchanged. The dismissal says this equals the base, which is true for the old Position::parse, but the PR introduced the strict parser and the author's own comment at gradient.rs:460-461 names the behaviour as invalid; REVIEW.md asks that a changed helper's sibling sites be fixed in the same PR. Remedy: call Position::parse instead of parse_bg_position in parse_at_position.
Verification: Pre-existing. parse_at_position (src/css/values/gradient.rs:463-465) calls Position::parse_bg_position, which accepts at left top 10px; Position::to_css prints it as 0 10px (position.rs:247-304). The strict Position::parse (position.rs:23-30) is not used for the gradient at clause. The base already turned at left top 10px into at 0 10px by the same route; to_css is unchanged by the diff.
…ee origin and position rows The shared length parser folds some math functions wrongly and reads a number without a unit as px. transform-origin, perspective-origin and mask-position never parsed before, so their new typed parse must not print such a value differently from before. - `parse_plain_value` in the property table declines a value that has a function or a number other than 0. The three rows use it. - `TransformOrigin.z` is the `LengthValue` that the other lengths of transform.rs use, so the file has one `Length` again. - The rows that were `test.todo` for these values now assert that the value stays as written.
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| /// `parse_value` for a row that reads no math function and no number without a unit. A value | ||
| /// with a function, or with a number other than `0`, stays as written: the shared length parser | ||
| /// folds some math functions wrongly (#38489, #46145, #45249) and reads `10` as `10px` (#42104). |
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If you need a paragraph-long comment to justify why the workaround is OK, the code is wrong — fix the code
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| /// A value for the [transform-origin](https://drafts.csswg.org/css-transforms-1/#transform-origin-property) property. | ||
| /// | ||
| /// lightningcss parses a `<position>` here, which reads the z offset of `left top 10px` as an | ||
| /// offset from the top. This type and its parser follow Stylo's `TransformOrigin` | ||
| /// (`style/values/specified/transform.rs`). |
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If you need a paragraph-long comment to justify why the workaround is OK, the code is wrong — fix the code
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| /// The x or the y offset of a [`TransformOrigin`]. Unlike a `<position>` component, a side | ||
| /// keyword takes no offset. |
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If you need a paragraph-long comment to justify why the workaround is OK, the code is wrong — fix the code
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| /// Parses the `at <position>` clause of a radial or conic gradient. | ||
| /// | ||
| /// The spec grammar is `<position>`. Like lightningcss, this still reads the three-component | ||
| /// form of `<bg-position>`, which is invalid here, and prints it with two components. |
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| /// Parses a [`<position>`](https://drafts.csswg.org/css-values-4/#typedef-position): | ||
| /// one, two or four components. | ||
| /// | ||
| /// lightningcss parses a `<bg-position>` everywhere. Stylo's `Position::parse` | ||
| /// (`style/values/specified/position.rs`) rejects the three-component form in the same way. |
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| /// Parses a [`<bg-position>`](https://drafts.csswg.org/css-backgrounds-3/#typedef-bg-position): | ||
| /// a `<position>`, or the three-component form (`left 10px top`). |
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The second commit addresses the earlier inline comments (the parse_plain_value pre-scan keeps math functions and unit-less numbers as written, TransformOrigin.z is now the file's single Length, and the former todo rows assert the as-written output), and this run found no new bugs. Because the PR adds a hand-written value grammar that intentionally follows Stylo rather than lightningcss, and itself frames that as a maintainer decision, a human look is still worthwhile.
What was reviewed:
parse_plain_valuein src/css/properties/properties_generated.rs: the token pre-scan saves and restoresParserStatethe same wayProperty::parsealready does for itsUnparsedfallthrough (soat_start_ofafter aFunctiontoken is rolled back), stops at the!importantdelimiter, and declines only onFunctionor a non-zeroNumbertoken.TransformOrigin::parsecontrol flow checked against Stylo'sTransformOrigin(center-first, keyword-first and z-after-two-components branches match); the strictPosition::parserejects exactly the three-value forms, since only those leave a side offset on one axis.- Every
Position::parsecaller: background-position, themaskshorthand and both gradientatclauses now useparse_bg_position; the strict parser is reached only from the perspective-origin and mask-position rows, andTransformOriginis registered incss_eql_partialeq!,generic_registrationsandbridge_deep_clone!. - Tests are additive only; no existing row was changed, and
attrTestexists in test/js/bun/css/util.ts.
Extended reasoning...
The change touches the CSS parser in src/css: a new TransformOrigin struct and OriginComponent enum with a hand-written parser and printer in src/css/properties/transform.rs, a strict/lenient split of Position::parse in src/css/values/position.rs with callers in background.rs, masking.rs and gradient.rs rerouted, three property-table rows retyped and a new parse_plain_value token pre-scan in properties_generated.rs, plus ~210 additive test rows. It touches no security-sensitive surface (no auth, injection or data exposure; input is CSS text already handled by the parser and the fallback is the pre-existing as-written path). The new commit resolved the four inline concerns from the prior review and the hunt ran dry with no new findings, which argues for a positive signal; the reason to still defer rather than approve is that the PR introduces a value type bun_css owns independently of lightningcss and makes a grammar-strictness choice the author explicitly presents as a maintainer decision, with no CODEOWNER covering src/css.
Still open from earlier reviews (1):
- Unresolved: 1 minor or pre-existing.
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### 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.
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Understood, this stays closed. On main the three properties still print their value as written, which is valid CSS, so no valid stylesheet is affected without this change. |
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Stacked on #45197.
Problem
transform-origin,perspective-originandmask-positionnever parse a real value..a{transform-origin:LEFT TOP}prints as written, and.a{transform-origin:STATIC}printsstatic.src/css/properties/properties_generated.rs:1825,:1830,:1844) use the keyword enum of thepositionproperty. No issue reports this.Fix
transform-origingets aTransformOrigintype (x, y, z). The other two rows use the x/yPosition, whoseparsenow rejects the three-value form. Other users keep it throughparse_bg_position.parse_plain_value).test/js/bun/css/css.test.ts(215 new rows, 158 fail before),test/js/bun/css/,test/bundler/css/. Self-reviewed: 22 concerns raised, 14 addressed (Notes).Background
<position>is an x and a y part. Onlybackground-positiontakes three values:left top 10pxis 10px from the top.transform-origina third value is a z length. lightningcss 1.33.0 printsleft top 10pxas0 10px. This PR follows Stylo instead.Downsides
perspective-origin:right 5pxprints the invalidright top 5px.calc()too, gets no type here and prints as written.transform-origin:50% 50%takes 3,516 instructions to parse (1,442 before) and saves one malloc. Other properties: +0.Notes
Repro
transform-origin:LEFT TOPLEFT TOP0 00 0transform-origin:STATICstaticSTATICSTATICmask-position:LEFT TOPLEFT TOP0 00 0transform-origin:left top 10px(z is 10px)0 0 10px0 10px(y is 10px)transform-origin:bottom right 5px(valid)100% 100% 5pxright 5px bottom(invalid)perspective-origin:center top 2px(invalid)50% 2px(valid)The mistake is one alias. The old Zig table had
const Position = position.Position;, wherepositionwas the module of thepositionproperty. The table now has no short name for that module, soposition::Positiondoes not compile in a row.Where this leaves lightningcss, and the decision for a maintainer
<bg-position>grammar. Itstransform-originrow has the comment// TODO: handle z offset syntax. The parser is Stylo'sPosition::parse_three_value_quirky.background-positiononly. ItsPosition::parserejects the three-value form (style/values/specified/position.rs). It has aTransformOrigintype with anOriginComponentfor x and y (style/values/specified/transform.rs). This PR has the same three pieces.perspective-originandmask-position(css/css-transforms/parsing/perspective-origin-invalid.html,css/css-masking/parsing/mask-position-invalid.html). They list the four-value forms as invalid fortransform-origin(transform-origin-invalid.html). The new test rows are those lists.Position::parsetakes fewer values than the lightningcss function of that name.perspective-originandmask-positionrows as they are here. It typestransform-originas aPosition, for its one and two value forms only.transform-originprints a side keyword as0or100%in every form. lightningcss keeps the keyword next to a length (right 10px,10px bottom). Three test rows pin this and say so.Measurements
Release builds (
bun-profile) of the #45197 branch and of this branch, same machine. Chrome is headless Chrome 153:CSS.supportsfor validity, and the computed value of the input against the computed value of the output.left,right,center,top,bottom,10px,20%,0) x 7 spellings = 32,760 cases, minified and pretty. 0 changed meanings, 0 valid values made invalid, 0 invalid values made valid, 0 outputs longer than the input.transform-origin140 of the 140 that Chrome takes,perspective-origin124 of 124,mask-position124 of 124.-webkit-mask-position124 of 196: Chrome takes the three-value form for that alias, and it stays as written here.transform-originvalues change meaning or become invalid. 42 invalidtransform-originvalues, 24perspective-originvalues and 24mask-positionvalues become valid.perspective-originandmask-positionprint the same text for 124 of 124.transform-originprints the same text for 46 of the 52 values without a z offset. The other 6 are the print choice above (1 or 2 bytes shorter).5, 2,700 values with a5):transform-origin,perspective-originandmask-positionprint all 2,700 as written.background-positionprints 94 of them withpx, before and after.background-position, thebackground,maskand-webkit-maskshorthands, and 8 gradient routes (@propertyinitial-value among them). 0 outputs differ from the base, 0 new parse errors.test/js/bun/css/fileshave 79transform-origindeclarations, 0 with a z offset, 0perspective-originand 0mask-position. Minified: 2,732,866 to 2,732,569 bytes (-297, -58 with gzip). 57 declarations change, and Chrome computes the same value for each changed text.doesnt_crash.test.tspasses (61 tests)..textofbun-profile105,710,585 to 105,716,729 bytes (+6,144,llvm-size). By symbol (llvm-nm):TransformOrigin+4,123, x/yPosition+3,864, keyword-list instantiations that are gone -2,212. The threeparse_plain_valueinstances are 4,105 bytes of that.size_of::<Property>()is 216 bytes before and after.size_of::<TransformOrigin>()is 40 bytes. The unparsed value it replaces is 48 bytes and owns a heap token list.Property::parsestack frame: 7,176 to 7,304 bytes, one page probe before and after (llvm-objdump).Property::parsecall (gdbsingle-step, three passes, base to this PR):width:10pxcolor:redbackground-position:left topbackground-image:radial-gradient(circle at left top, red, blue)mask:url(a.png) left top 10pxtransform-origin:left toptransform-origin:left top 10pxtransform-origin:centertransform-origin:50% 50%transform-origin:var(--x)transform-origin:calc(50% + 10px) toptransform-origin:inheritperspective-origin:left topperspective-origin:left 10px top 20pxmask-position:left topmask-position:left top, right bottom-webkit-mask-position:left top 10px(stays as written)Some rows vary by up to 36 instructions between passes. The table has the most frequent count. The check for a function or a unit-less number reads the value once more, which is about 550 of the instructions of
transform-origin:left top.Not changed here, on purpose
at <position>still takes the three-value form, which is invalid there, and prints it with two values. lightningcss does the same. A strict parse is one line, but it changes existing output. The gradient then stays as written, and an@propertyrule with such an initial-value becomes a build error. css: read an @property initial-value on the stylesheet's parser, keep an unmatched value as written #45806 changes how an unmatched initial-value is handled. Twotest.todorows mark this, with the text they print today.maskshorthand still takes the three-value form. Chrome accepts it there and Stylo does not.-webkit-mask-positionwith three values stays as written.margin-left:rem(10px,3em)prints0andmargin-left:max(1px + 2em)prints1px + 2em. It also reads10as10px. The three rows printed such a value as written until now, soparse_plain_valuein the table keeps it that way. css: keep math functions over two different length units as written #38489, css: wrap a one-argument min()/max() sum in calc() and give hypot() one fold for every argument count #46145, css: fold round() by choosing between the lower and upper multiple of |B| #45249 and css: treat out-of-range and unit-less numeric values as invalid instead of merging or repairing them #42104 have the corrections. After them the three arms can callparse_value.Property::to_cssandProperty::eqlare the only readers, so no vendor prefix is added here. css: dispatch each declaration to the handler that owns its property #45747 and css: treat out-of-range and unit-less numeric values as invalid instead of merging or repairing them #42104 edit the same table.Tests
css.test.tshas two new blocks: 215 rows and 2test.todorows. On a release build of the css: stop rewriting valid positions into ones browsers reject #45197 branch 158 rows fail and 57 pass. The 57 are 55 values that must stay as written and 2 guards forbackground-positionand themaskshorthand.test/js/bun/css/css.test.tsanddoesnt_crash.test.tswith the debug build.test/js/bun/css/andtest/bundler/css/(29 files) with the release build of this branch.Self-review: the 8 concerns not taken
transform-origininto its own PR on main (2). One alias caused the three rows, so they stay together.