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Found 1 issue this PR may fix:
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No bugs found, but deferring to a human — this is a ~230-line feature fill-in for previously-stubbed CSS-module composes semantics, and I'd like a human to confirm the design choices.
What was reviewed:
handle_composesbuilds Local/Global/Dependency refs and inserts intoexports_by_source_index— matches the siblingadd_local/get_reference/reference_dashedpatterns and lightningcss shape.- Export-key concern (mangled vs original name via
lookup_ident_or_ref→lookup_symbol) checked: falls through tooriginal_namewhenlocal_namesis empty, so test path is correct. - Caller in
rules/style.rsalreadytake()sdest.css_modulebefore the call, so the added&mut destparam doesn't alias.
Two things worth a human eye: (1) the fails-on-main evidence only shows cssModulesTest is not a function — it proves the test helper is new, not that the stubbed handle_composes was the failure; (2) nothing in production appears to read CssModuleExport.composes yet (bundler uses the separate ast.composes path), so it's worth confirming this is the intended consumer surface.
Extended reasoning...
Overview
Implements the previously-stubbed CssModule::handle_composes in src/css/css_modules.rs so that composes: declarations populate CssModuleExport.composes with Local/Global/Dependency references. Adds a test-only cssInternals.cssModulesTest binding (src/css_jsc/css_internals.rs, internal-for-testing.ts, dispatch_js2native.rs) to surface ToCssResult.exports to JS, plus a 5-case test file.
Security risks
None. No untrusted-input parsing changes, no new syscalls, all new JS surface is behind bun:internal-for-testing.
Level of scrutiny
Medium. The core change is ~55 lines of new logic in the CSS-modules printer path plus ~120 lines of test-only JSC glue. The logic itself is a faithful port of lightningcss's handle_composes and reuses existing helpers (pattern.write_to_string, entry() API, eql for dedupe) consistent with sibling functions in the same file. But it is a feature implementation rather than a mechanical fix, and the semantics (what key the export lands under, how it interacts with the bundler's local_names map when non-empty) have downstream implications once something consumes .composes.
Other factors
- Test validity: the fails-on-main log shows
TypeError: cssModulesTest is not a function, i.e. the tests fail because the helper binding doesn't exist on main, not becausehandle_composeswas a stub. Per REVIEW.md's "confirm deleting each load-bearing clause of your fix breaks at least one test", this doesn't demonstrate that reverting onlycss_modules.rs(keeping the helper) would fail the tests. It almost certainly would — the stub returned an emptycomposes— but the evidence doesn't show it. - Liveness: grepping for consumers of
ToCssResult.exports/.composesturns up only the new test helper. The PR description explicitly notes the bundler'scomposes:support is a separate parser-level path (ast.composes). REVIEW.md asks "trace new state to an actual consumer"; a maintainer should confirm this map is intended to be consumed (e.g. by a futureBun.buildCSS-modules exports API, or #19663's fix path) rather than being populated with no reader. - Export-key semantics:
lookup_ident_or_refconsultslocal_namesbeforeoriginal_name. In the test pathlocal_namesis empty so the key is the original class name; in a bundler context with a populated map it would be the mangled name. Verifiers ruled this out as a bug for the current PR, but it's a design point worth a maintainer's sign-off before something starts reading the map.
Given it's a non-trivial feature fill-in with open questions on consumer/liveness and test-validity evidence, I'm deferring rather than auto-approving.
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Addressing the two review points: (1) Test validity. Verified that reverting only The one passing test is the invalid-selector error, which the stub already handled. So the (2) Consumer surface. Correct that Export-key note. |
handle_composes previously only validated that the selector was a single
class; the body that builds the composed references was never ported. As
a result CssModuleReference::{Local, Global} were never constructed and
CssModuleExport.composes was always empty in ToCssResult.exports.
This fills in the body to match lightningcss: for each single-class
selector and each composed name, construct a Local (same-file, hashed),
Global (composes: x from global), or Dependency (composes: x from
"./file.css") reference and append it to the selector's export entry,
de-duplicating by value.
Adds a cssInternals.cssModulesTest helper that parses a string with CSS
modules enabled and returns {code, exports} so the composes list can be
asserted from JS. The bundler's composes support goes through a separate
parser-level path (ast.composes) and is unchanged.
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I didn't find any bugs, but this needs a maintainer call: the author explicitly flags that CssModuleExport.composes has no in-tree consumer (the bundler uses the parser-level ast.composes path), so whether to populate this map vs. delete the Local/Global variants per #36184's dead-code sweep is a design decision, as is the open export-key question (mangled vs. original name via lookup_ident_or_ref).
What was reviewed:
handle_composesborrow pattern — caller inrules/style.rsalreadytake()sdest.css_modulebefore the call, andlookup_ident_or_refdoesn't touch it, so no aliasing.- Arena lifetimes in the new code — all allocations go through
dest.arena/bump.alloc_slice_copy, matching sibling methods. - The new
css_modules_testbinding follows the same'bump-erasure and error-path shape astesting_impl/attr_testin the same file.
Extended reasoning...
Overview
This PR implements the previously-stubbed CssModule::handle_composes in src/css/css_modules.rs (~60 lines) to construct CssModuleReference::{Local, Global, Dependency} entries for each name in a composes: declaration and append them to the selector's CssModuleExport.composes list. To test it, it adds a ~120-line css_modules_test internal-for-testing binding in src/css_jsc/css_internals.rs (plus wiring in internal-for-testing.ts and dispatch_js2native.rs) and a 47-line test file covering local/global/dependency/dedupe/invalid-selector cases.
Security risks
None. This is CSS Modules metadata construction inside the printer; no untrusted-input parsing changes, no filesystem/network access, and the only new JS-reachable surface is gated behind bun:internal-for-testing.
Level of scrutiny
Medium-to-high, driven not by risk of breakage (the populated map has no production reader) but by the design question the author explicitly leaves open. The Local/Global variants were flagged as never-constructed by the dead-code sweep in #36184; this PR resolves that by making them constructed rather than by deleting them, and adds a test-only JSC binding as the sole consumer. REVIEW.md's "Every line you add must be demonstrably live" and "trace new state to an actual consumer" apply directly here — a maintainer should confirm that filling in the lightningcss-shaped ToCssResult.exports map is the intended direction (vs. deleting the dead path or wiring it into the bundler), and settle the export-key semantics the author raised.
Other factors
- The caller in
src/css/rules/style.rs:211-227already handles the&mut self/&mut destaliasing viadest.css_module.take(), andlookup_ident_or_refreads onlysymbols/local_names, so the newdestusage is sound. - The author verified the
css_modules.rschange is load-bearing by reverting it in isolation (4/5 tests fail), which is stronger evidence than theUSE_SYSTEM_BUN=1gate output shown in the PR body (that only proved the new binding is absent on main). - Bundler CSS-modules tests (
test/bundler/css/css-modules.test.ts,test/bundler/esbuild/css.test.ts) reportedly still pass, consistent with the bundler using the separateast.composespath.
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Updated 5:39 PM PT - Jul 28th, 2026
❌ @robobun, your commit 7f7c0f6 has some failures in 🧪 To try this PR locally: bunx bun-pr 36225That installs a local version of the PR into your bun-36225 --bun |
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No bugs found, but deferring to a human reviewer. The PR itself flags an open design question — CssModuleExport.composes has no in-tree consumer (the bundler uses the separate ast.composes path), so whether to populate it (this PR) versus delete the never-constructed Local/Global variants flagged in #36184 is a maintainer call, as the author notes. The export-key choice (lookup_ident_or_ref, which returns the mangled name under bundler-populated local_names) is another deferred decision that depends on which consumer, if any, is planned.
What was reviewed
handle_composescontrol flow against the caller inrules/style.rs— thecss_module.take()dance means&mut selfand&mut destdon't alias; error is returned after the module is put back.- Arena ownership:
name_bytesandspecifierarebump.alloc_slice_copy'd,idcomes fromlookup_ident_or_refwhich yields an'aslice; nothing borrows a temporary. - The new
css_modules_testhelper mirrorstesting_impl/attr_teststructure (same'bump-erasure, same log/import-record wiring,init_with_one_list(extra.symbols)so refs resolve).
Extended reasoning...
Overview
The PR implements CssModule::handle_composes in src/css/css_modules.rs (previously a validation-only stub) so that composes: declarations populate CssModuleExport.composes with Local / Global / Dependency references. To test it, a new cssInternals.cssModulesTest binding (~120 lines of Rust in css_internals.rs, plus dispatch and internal-for-testing wiring) exposes the printer-side exports map to JS, and 5 new tests exercise local/global/dependency/dedupe/error paths. ~230 lines net.
Security risks
None. No user-facing API surface changes; the only new JS-reachable code is behind bun:internal-for-testing, which is gated to debug builds and CI. Inputs to handle_composes come from the CSS parser, and index accesses (hashes[source_index], import_records[idx]) are bounded by parser-produced indices as elsewhere in the file.
Level of scrutiny
Medium-high. The Rust change itself is straightforward and closely follows the neighboring get_reference / add_local / reference_dashed patterns (arena-copied slices, entry() API, pattern.write_to_string). Correctness looked fine: the caller in rules/style.rs:211-229 moves dest.css_module out before the call so the two &mut borrows don't alias, and it restores it before propagating the error via dest.new_error. All stored slices are either arena-allocated in this call or already 'a-lifetime.
However, this is not a mechanical fix — it's a ~60-line feature implementation whose purpose is under discussion. The author's own follow-up comment states CssModuleExport.composes has no in-tree consumer today and that whether to keep populating it vs. wiring a consumer is "a maintainer call." REVIEW.md's dead-code guidance ("delete dead code in the same PR that makes it dead") points the other direction from #36184's flag. That's an architectural decision I shouldn't make unilaterally.
Other factors
- The export-map key is derived via
dest.lookup_ident_or_ref(*id), which the author notes returns the mangled name whenlocal_namesis populated (bundler context). Lightningcss keys on the original name. Since no consumer exists, either choice is defensible right now, but a maintainer should confirm the intended shape before this becomes load-bearing. - Test validity was independently verified by the author (reverting only
css_modules.rsfails 4/5 tests), so the new tests do exercise the load-bearing change and not just the new binding. - The
css_modules_testhelper is test-only and structurally identical to the existingtesting_impl/attr_test, so the unsafedetach_lifetime_refand log-pointer patterns are pre-approved shapes in this file.
Given the open "populate vs. delete" question that the author explicitly punted to maintainers, this warrants human sign-off rather than auto-approval.
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Closing this PR because it has been inactive for more than 90 days. |
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This PR stays closed.
The code that is left around |
### 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.
What
CssModule::handle_composesinsrc/css/css_modules.rswas a validation-only stub: it checked thatcomposes:appears under a single class selector but never built the composed references.CssModuleReference::{Local, Global}were never constructed anywhere (flagged by the dead-code sweep in #36184) andCssModuleExport.composeswas always empty in theToCssResult.exportsmap.Fix
For each single-class selector and each name in the
composes:list, construct the appropriate reference and append it to the selector's export entry (creating the entry on first use), de-duplicating by value:composes: …alphaLocal { name: pattern.write_to_string(.., "alpha") }x from globalGlobal { name: "x" }x from "./other.css"Dependency { name: "x", specifier: record.path.text }This matches the lightningcss
handle_composesbehavior. Note that Bun'sSpecifierhas noSourceIndexvariant, so that lightningcss arm does not apply here.The bundler's
composes:support is a separate parser-level path (ast.composesconsumed bygenerateCodeForLazyExport/scanImportsAndExports) and is unchanged;handle_composespopulates the printer-sideToCssResult.exportsmap.Testing
Added
cssInternals.cssModulesTest(source)(internal-for-testing only) which parses withcss_modules: Some(Config::default()), wires the parsed symbol list intoto_css, and returns{ code, exports }where each export carries itscomposesarray. New tests intest/js/bun/css/css-modules-composes.test.tscover the local / global / dependency / multi-name-dedupe cases plus the existing invalid-selector error.Existing
test/bundler/css/css-modules.test.ts(6 pass) andtest/bundler/esbuild/css.test.ts(56 pass) are unchanged.[review] gate passed · iteration 1 · 5 files touched
fails on main (without fix)
passes on PR (with fix)
diff hotspot
gate history · 2 passed · 0 rejected · iteration 1
evidence per changed file