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css: derive equality for Size2D and BorderRadius, and keep every prefix in the border-radius handler - #45665
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css: derive equality for Size2D and BorderRadius, and keep every prefix in the border-radius handler#45665robobun wants to merge 5 commits into
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…order-radius handler
`Size2D::eql` compared the first component of the left value with the
second component of the right value. Two values were equal when those
two matched, whatever the other two were. The minifier merged
neighbouring rules whose `border-spacing` or `border-radius` differ,
and `@font-face { font-style: oblique 14deg 20deg }` printed as
`oblique`. It now compares the first components and the second
components, as lightningcss does.
With the comparison correct, equal elliptical radii reach the branch of
`BorderRadiusHandler` that updates a value in place. That branch
replaced the set of vendor prefixes with the prefix of the last
declaration, so `border-radius: 10px; -moz-border-radius: 10px` kept
only the `-moz-` declaration. It now adds the prefix to the set, as
lightningcss and the other prefix handlers do.
`Size2D` and `BorderRadius` now derive `PartialEq`, as they do in lightningcss. The hand-written `Size2D::eql` and `BorderRadius::eql` are gone, and their four users compare with `==` and `!=`. The output does not change.
…cases The border-radius group of the lightningcss test suite was not in the port. It is now, and three of its cases fail without the handler fix. The new cases cover a difference in the first component only, rules inside `@media`, `!important` lists, the `bun build` entry point, and the prefix rule that the handler shares with lightningcss.
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No actionable comments were generated in the recent review. 🎉 ℹ️ Recent review info
Walkthrough
ChangesCSS equality and prefix handling
Priority: ➖ Normal Merge Risk: ⚪ Minimal · up to
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Check skipped because no linked issues were found for this pull request. |
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| Title check | |
The title clearly summarizes the main changes: deriving equality for Size2D and BorderRadius, and preserving all vendor prefixes in the border-radius handler. |
| Description check | |
The description is detailed and covers the problem, implementation, verification steps, tests, measurements, and known downsides. It does not use the exact template headings, but it provides the requi… |
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The description is detailed and covers the problem, implementation, verification steps, tests, measurements, and known downsides. It does not use the exact template headings, but it provides the required information in equivalent sections.
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Updated 9:18 AM PT - Oct 18th, 2026
✅ @robobun, your commit f1c0c529c1e4b3b127f3d3a1c6887f2f62f2095c passed in 🧪 To try this PR locally: bunx bun-pr 45665That installs a local version of the PR into your bun-45665 --bun |
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Status: the bug is reproduced, and this PR has the fix. Reproduction on bun 1.4.3-canary (367d939) and on a release build of main (5866b5f): printf '.table { border-spacing: 0 }\n.rows { border-spacing: 0 8px }\n.x { border-radius: 4px; -webkit-border-radius: 4px; -moz-border-radius: 4px }\n' > in.css
bun build ./in.css --minify --outdir out && cat out/in.css
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![claude[bot]](https://avatars.githubusercontent.com/in/1236702?s=60&v=4){kind=small}
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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 sibling handlers for the same prefix-set overwrite (flex.rs:558, align.rs:980, box_shadow.rs:218 already insert the prefix, so border_radius.rs was the only outlier), confirmed no callers of the deleted Size2D::eql/BorderRadius::eql remain, and that #[derive(PartialEq, Eq)] on Size2D<T> adds no bound the existing CssEql for Size2D<T> bridge (T: Clone + PartialEq) did not already require. Both inline findings concern the flush rule shared with lightningcss, which the PR description lists as a known downside and the new tests pin.
Extended reasoning...
The change deletes a miscomparing hand-written Size2D::eql (compared lhs.a == rhs.b) and BorderRadius::eql in favour of derived PartialEq, rewires the CssEql bridges and two call sites (maybe_flush!, font_face oblique default), and makes property_helper! insert the incoming vendor prefix instead of replacing the set. No security-sensitive surface is touched; this is CSS minifier value comparison and vendor-prefix bookkeeping. Two inline findings about the lightningcss-inherited flush semantics are already posted, so the body only records what else was examined and ruled out.
![github-actions[bot]](https://avatars.githubusercontent.com/in/15368?s=60&v=4){kind=small}
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A second report of this prefix loss came in while this PR was open. It is the same defect at The script of the report. It runs
The three control rules print the same with both builds. More declaration lists. I compared 26 border-radius declaration lists with lightningcss 1.32.0, each with the default browser targets and with Suites. |
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#46086 covers the two-value Its base is this branch. The two changes merge with no Git conflict, but they disagree in two cases that this PR ports from lightningcss: with #46086, Merge this PR first, then retarget #46086 to |
Jarred-Sumner
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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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Verified on main at 7942008 with a debug build.
Nothing is left to do here. |
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Problem
bun builddropsborder-radiuswhen a prefixed copy follows it:border-radius:4px;-webkit-border-radius:4px;-moz-border-radius:4px(bootstrap-table 1.11.1) prints-moz-border-radius:4px, which no current browser reads.property_helper!(src/css/properties/border_radius.rs:201): it replaces a corner's prefix set.Size2D::eql(src/css/values/size.rs:80) islhs.a == rhs.b:.table{border-spacing:0}.rows{border-spacing:0 8px}prints.table,.rows{border-spacing:0}. I found no real stylesheet that shows it (Notes).Fix
Size2DandBorderRadiusderivePartialEq, as in lightningcss. Their hand-writteneqlis gone.test/js/bun/css/css.test.ts(27 new cases fail on main),test/bundler/esbuild/css.test.ts(4). Alsotest/js/bun/css,test/bundler/css. Self-reviewed: 6 concerns raised, 6 addressed here.Background
Size2D<T>holds two components, such as the two radii of a corner.BorderRadiusHandlerbuffers the radii of one rule: a value and a prefix set for each corner.Downsides
allafter a radius:.a{border-radius:1px;all:unset;-moz-border-radius:1px}now prints.a{all:unset;border-radius:1px}. Main hoistsalltoo (css: make theallshorthand reset the declarations before it #42042) but hid this..textgrows by 1,536 bytes.Notes
Questions for a maintainer
existing.1 != $vpin place of!existing.1.contains($vp)inmaybe_flush!. I measured it on the radius corpus:The stricter rule is never worse than this change in Chrome on this corpus. Its costs are the difference from lightningcss and the size. The transform, box-shadow, flex, align and transition handlers would keep the lightningcss rule. Three of the new tests pin the lightningcss rule and would change. Say so if you want the stricter rule in this PR.
Real stylesheets
I built 9,062 stylesheets of 369 npm packages with release builds of main and of this change.
-moz-, which no current browser reads. Example:.nihilo .dijitTabContainerTop-tabs .dijitTabin dijit prints-moz-border-radius: 4px 4px 0 0on main andborder-radius: 4px 4px 0 0now. In the other packages main keeps a-webkit-copy, which current browsers still read, or drops a radius of 0..fixed-table-containerrule is the example in Problem.--target=bun: the output changes in 112 files of 22 packages. Most of them keep a prefixed copy that main dropped..v-locale--is-rtl .rounded-ts-shaped{border-top-right-radius:24px 0}and.v-locale--is-ltr .rounded-te-0{border-top-right-radius:0}become one rule on main. Both values paint a square corner, so nothing changes on screen. I found no real stylesheet where the merge is visible.test/js/bun/css/files(2.9 MB) are byte-identical to main, with and without targets.More symptoms of the comparison, all fixed
@font-face{font-style:oblique 14deg 20deg}printsoblique, because the comparison with the default14deg 14degis the same function..a{border-spacing:4px 8px}.b{border-spacing:8px 4px}and.a{border-spacing:4px 8px}.b{border-spacing:8px}merge. Two rules that both have0 8pxdo not merge.@media, and in!importantlists.--target=bunor--target=node. With the default browser target they compile to:lang()rules that do not merge..a{-webkit-border-top-left-radius:10px 20px;border-top-left-radius:20px 10px}prints onlyborder-top-left-radius:20px 10px.border-start-start-radius:5px 10px;border-start-end-radius:10px 5pxgives one rule for left-to-right and right-to-left on main. No release build reaches this case, becausebun buildhas no option for the browser targets.#[derive(Debug, Clone, PartialEq)] pub struct Size2D<T>(pub T, pub T);and*val = $val.clone(); *prefixes |= *$vp;(master ab14f90df4).Why the two changes land together
The wrong comparison says that two equal elliptical radii differ. The handler then flushes between them, and that hides the line that replaces the prefix set. The corpus is 34,422 sequences of radius declarations in one rule: each single declaration, each pair, and 30,000 random sequences of three to five. The declarations are
border-radiusand the four physical longhands, with no prefix,-webkit-or-moz-, and circular or ellipticalpxvalues. The table counts the sequences that end with a wrong radius in one of four models: only unprefixed declarations apply, only-webkit-, only-moz-, and unprefixed with-webkit-as one property.These models read
-webkit-border-radiuswith the standard grammar. Chrome and Safari do not: they read-webkit-border-radius: a basa / b(a legacy rule in Blink and WebKit). So I also measured the computed style in headless Chrome 153.0.8010.52, with and without the default targets (the counts are the same):I did not run Firefox or Safari.
The cases that were right on main
They have two causes. Both are in lightningcss too, and main avoided them only because it dropped the prefix set.
maybe_flush!, upstreamborder_radius.rs:124): the handler flushes only when the value differs and the set does not contain the incoming prefix. When the set contains it, the new value replaces the value of each prefix in the set..a{-moz-border-radius:1px;border-radius:1px;-moz-border-radius:2px}prints.a{-moz-border-radius:2px;border-radius:2px}, and.a{border-radius:2px}with the default targets. Main printedborder-radius:1px;-moz-border-radius:2px. The transform, box-shadow, flex, align and transition handlers use this rule on main. Two tests pin this output and name the rule.-webkit-border-radius:.a{border-radius:1px 2px;-webkit-border-radius:1px 2px}prints.a{border-radius:1px 2px}with the default targets. Chrome computes1px 2pxfor each corner of the source and1px | 2px | 1px | 2pxfor the output. Main printed-webkit-border-radius:1px 2px.For three rules with one selector and the default targets, lightningcss minifies again after each merge and prints
.a{border-radius:1px;-moz-border-radius:2px}. Bun minifies once after the last merge (flush_pending_style_merge) and prints.a{border-radius:2px}. Main does the same today for transform and box-shadow:.a{-ms-transform:rotate(1deg)}.a{transform:rotate(1deg)}.a{-ms-transform:rotate(2deg)}builds to.a{transform:rotate(2deg)}. This change does not touch that. AcssTestTodorecords the border-radius case.allBun prints
allabove the declarations that a handler still buffers..c{border-radius:4px;all:unset}prints.c{all:unset;border-radius:4px}on main and with this change. #42042 is the change for that. When a-moz-copy follows, main replaced the prefix set and printed.a{all:unset;-moz-border-radius:1px}, which Chrome computes as 0px, like the source. This change prints.a{all:unset;border-radius:1px}(1px in Chrome), and.a{all:unset;-moz-border-radius:1px;border-radius:1px}with--target=bun.Measurements
.text: +1,536 bytes (llvm-size -Aonbun-profile, main 5866b5f against this change, one tree). Six functions change size, +1,576 bytes and +428 instructions in total.BorderRadiusHandler::handle_propertyis +1,096 of the bytes.Length), 33 to 66 (LengthPercentage). One minify pass over the 15 stylesheets calls it 48 times with no targets and 56 times with the default targets, plus 35 calls of theBorderRadiusequality. Main makes the same number of calls. For 1,000, 2,000 and 4,000 neighbouring rules the count is 999, 1,999 and 3,999 (gdb hit counters, debug build).perf,valgrindandbloatyare not installed here.Tests
test_border_radiusgroup of lightningcss was not in the port. It is now (25 cases). Three of them fail on main.css.test.tsequals the output of lightningcss 1.33.0.bun buildhas no option for the browser targets.css-fuzz.test.tshas three cases with a 10 s limit that the debug build does not meet on my machine. They also time out on a debug build of main.Found and not changed here
-webkit-border-radius(above, css: keep the legacy two-value-webkit-border-radiusas its own declaration and print other-webkit-radii with three values #46086 has a change for it). Bun and lightningcss parse it with the standard grammar..a{-webkit-border-radius:10px 100px 10px 100px}prints.a{-webkit-border-radius:10px 100px}on main and with this change, and Chrome reads that as10px / 100px. One ported lightningcss case expects this output.impl PartialEq for PropertyIdignores the name of a custom property (css: compare custom property names inPropertyIdequality and importance in duplicate-rule detection #33684 has a change for it)..a{transition-property:fill}.b{transition-property:stroke}merges.@font-face{font-style:oblique 15.5555556grad}printsoblique 15.5556grad. lightningcss compares angles in degrees and printsoblique. The output is valid.LengthValue::try_op(css: keep math functions over two different length units as written #38489), the@supportsmerge (css: parse (property: value) @supports conditions as declarations and merge same-condition rules #38589) and negative radii (css: treat out-of-range and unit-less numeric values as invalid instead of merging or repairing them #42104) have open changes.