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The CSS printer does not see the final path of a copied asset. It prints a placeholder and the bundler replaces it with the output path after printing. With --minify the placeholder was printed as an unquoted url(), so a final path with a space, a quote or a parenthesis became a bad-url token and the browser dropped the declaration. Print a placeholder inside a quoted string in every mode. Real urls (external, data:) are still printed unquoted when that is shorter.
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WalkthroughCSS bundling now resolves placeholder status, normalizes asset paths, and applies content-aware escaping. Metafile output uses raw paths. Sizing and source-map shifts track emitted bytes. Tests cover special characters and emitted assets. ChangesCSS URL serialization
Suggested reviewers: Priority: ➖ Normal Merge Risk: ⚪ Minimal · up to
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| Check name | Status | Explanation |
|---|---|---|
| Title check |  |
The title clearly identifies the main change: quoting and escaping asset paths inserted into CSS url() values. |
| Linked Issues check | |
Check skipped because no linked issues were found for this pull request. |
| Out of Scope Changes check | |
Check skipped because no linked issues were found for this pull request. |
| Description check | |
The description clearly explains the problem, implementation, scope, limitations, and verification results. It does not use the template headings exactly, but it includes the required information, inc… |
Full details: Description check
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Explanation
The description clearly explains the problem, implementation, scope, limitations, and verification results. It does not use the template headings exactly, but it includes the required information, including how the code was verified.
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Updated 10:05 PM PT - Oct 21st, 2026
❌ @robobun, your commit dc851b2 has some failures in 🧪 To try this PR locally: bunx bun-pr 41557That installs a local version of the PR into your bun-41557 --bun |
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LGTM — the earlier doc-comment nits were addressed in ef19ade and a619873, and this run found nothing further.
What was reviewed:
resolve_import_record_urlbranches:is_placeholderistrueonly for the unique-key/copied-asset branch; the inlineddata:URL and external-URL branches correctly stayfalse, so they still get the shorter unquoted form when safe.- Both
url()emission sites (values/url.rsandproperties/custom.rs) gate on!is_placeholder; theunsafelifetime-detach blocks are unchanged in what they borrow. - The updated
URLQueryFragmentPreservedMinifiedexpectation is a legitimate consequence (that asset is a placeholder), not a weakened test; the new test usesitBundled,Buffer.alloc(n, fill), and covers space, parens, custom-property, and a plain-name control case.
Extended reasoning...
Overview
The PR fixes a CSS minifier correctness bug: when --minify is on, copied-asset url() references were emitted unquoted based on the placeholder text (which has no special chars), then the bundler spliced in the real output path afterwards — producing an invalid bad-url token if the path contained a space or parenthesis. The fix threads an is_placeholder flag out of the printer's import-record resolver via a new ResolvedImportRecordUrl struct, and both url() printing sites (src/css/values/url.rs and src/css/properties/custom.rs) skip the unquoted-url optimization when the URL is a placeholder. get_import_record_url remains as a thin wrapper for callers that only need the bytes.
Security risks
None. This is output-formatting logic in the CSS printer; no untrusted-input parsing, no auth/crypto/permissions surface. The unsafe blocks touched are pre-existing lifetime-detach patterns whose borrowed data (resolved.url) is the same arena-backed slice as before — only the wrapping struct changed.
Level of scrutiny
Low-to-moderate. The diff is ~50 lines of code plus a test. The mechanism is straightforward (add a boolean, branch on it), and the PR description precisely names the root cause and the alternative considered. I checked that all three return branches of resolve_import_record_url set is_placeholder correctly: only the unique_key_for_additional_file branch (post-print splice target) is true; inlined data: URLs and external URLs are the final text and correctly stay false, preserving the existing minification for them. Per REVIEW.md's "fix the whole class" rule, both sibling url() printers are updated; the PR notes that image-set() and css-modules composes already go through serialize_string and were unaffected.
Other factors
The new itBundled test lives in the right file, uses Buffer.alloc(n, fill).toString() per repo convention, and covers the variant matrix (space, parentheses, custom-property token path, and a plain filename as a control). The one changed existing assertion (#icon fragment test now expects quoted form) is a direct, explained consequence of the fix — that asset resolves through the placeholder branch — not a silent weakening. The two follow-up commits after the earlier inline comments were doc-comment adjustments only; the logic has not changed since the initial commit. No CODEOWNERS entry covers these paths and there are no outstanding third-party changes-requested reviews.
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Status: ready for review. The branch has current Two forms of one bug, both reproduced on bun 1.4.3:
A placeholder is now always printed inside a quoted string, and the join in The last push merges CI (build 130480): 179 jobs passed and none failed. The two macOS x64 test jobs expired before an agent took them, so that lane did not run. The tests the build lists as failed passed on a retry or when run alone, and none of them is in the code this PR changes. |
…g it lands in
The CSS printer writes a placeholder for a copied asset inside a quoted
string, and the chunk join replaces it with publicPath + output path
verbatim. The [name] part of that path is the asset's file name, so a
quote or a line break in the name ended the string. A crafted name such
as x");}body{color:red}a{b:url("y.png injected a whole rule.
For CSS chunks, the count pass and the write pass of the join now run
both parts of the path through the CSS string serializer. The count
pass also applies the same separator normalization as the write pass,
so the two agree on the escaped length.
robobun
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Actionable comments posted: 1
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Inline comments:
In `@test/bundler/esbuild/css.test.ts`:
- Around line 1325-1327: Update the expected array in the asset-name assertion
to apply the same -[hash].png stripping as the actual names, so it compares
“a\nb” and injection rather than hashed values. Preserve the existing sorting
and asset collection logic.
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📒 Files selected for processing (6)
src/bundler/Chunk.rssrc/css/css_parser.rssrc/css/printer.rssrc/css/properties/custom.rssrc/css/values/url.rstest/bundler/esbuild/css.test.ts
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TOML.parse was missing `defer log.deinit()` after `Log.init`, causing the logger's internal message ArrayList to leak on every call that produces parse errors. All peer parsers (JSONC, JSON5, YAML) already have this defer. Also modernized argument access from `callframe.arguments_old(1).slice()` to `callframe.argument(0)` to match the JSONC parser pattern. Crash fingerprint: `49da9789c26e29ab` --- Verification: Confirmed `main` has `Log.init` on line 30 with no matching `defer log.deinit()`. All peer parsers (JSONCObject.zig:31, JSON5Object.zig:70, YAMLObject.zig:951) pair `Log.init` with `defer log.deinit()`. The `log.toJS` + `defer log.deinit()` combination is safe (same pattern in JSONCObject.zig:31+44). Argument modernization to `callframe.argument(0)` matches JSONCObject.zig:32 exactly. Regression test exercises the error path with non-string input and GC. No TODO/FIXME/HACK in diff. Lint JS and pipeline passed; buildkite build oven-sh#41538 compiling (trivial one-line semantic change, adding a missing defer). --- Reviewer verification (robobun): Independently confirmed TOMLObject.zig on main (line 30) has `Log.init` with no `defer log.deinit()`, while peer JSONCObject.zig (lines 30-31) pairs them correctly. The diff adds exactly that missing defer and modernizes argument access to match JSONCObject.zig:32. No TODO/FIXME/HACK in added lines. Bot reviews (claude x2, coderabbit) all LGTM with no blocking issues. Test exercises the modified error paths with non-string inputs. CI: Lint JS pass, pipeline pass, buildkite build oven-sh#41557 compiling on commit 12daf4b. --------- Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
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#45604 adds one return to the body of This PR moves that body into |
…quote-asset-url-placeholder # Conflicts: # src/bundler/Chunk.rs
… raw The join chose the CSS escape from a boolean on the chunk it was given. The metafile is built through the same join with a stand-in chunk, so a CSS-only build ran the metafile join with the CSS escape on. The join now takes a SpliceEscape. SpliceEscape::for_chunk is an exhaustive match on the chunk kind, and the metafile calls the new code_for_metafile, which passes Raw. The sizing pass and the writing pass share spliced_path_parts and write_spliced_path, so both see the same bytes, and platform_to_posix_buf borrows the path on POSIX in place of a copy per placeholder. Tests: exact output in place of a whitespace-insensitive match, an @font-face rule, image-set(), [dir] asset naming with an ordinary publicPath, and a file name chosen by a dependency's exports.
…quote-asset-url-placeholder # Conflicts: # src/bundler/Chunk.rs
…quote-asset-url-placeholder
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#46511 adds the test |
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Problem
bun build --minifyprints a copied asset as an unquotedurl():.a{background:url(./my image-2pc7w5rx.png)}, a bad-url token that bun itself rejects:error: Unexpected token: url(./my image-2pc7w5rx.png). In@font-facethesrcvanishes silently.publicPathreplace the placeholder verbatim. A dependency'sexportscan pick a file namedx");}body{color:red}a{b:url("y.png, which adds a rule.Fix
src/bundler/Chunk.rstakes aSpliceEscapeper chunk kind. A CSS chunk writes the spliced text through the CSS string serializer. esbuild copies it raw: a deliberate departure.css/FileLoaderURL*cases intest/bundler/esbuild/css.test.tsfail on the released build. Also the bundler CSS, HTML and metafile suites.Background
url(path)is one token and cannot hold whitespace, quotes or parentheses.url("path")takes a string.SpliceEscape::Raw. bundler: JS-escape file-loader asset paths at chunk assembly #34188, bundler: escape what is spliced into JS chunks (ASCII for bun), and fix the column count source map shifts use after non-ASCII text #38666 and bundler(html): percent-encode output paths written into src and href, and serve them under that name #41793 add their escapes there.Downsides
url().publicPathwith",\or a control byte now prints escaped in CSS.#,?,%, a tab or a line break does not load in a browser.Notes
Repro, unquoted form (bun 1.4.3):
With the fix:
.a{background:url("./my image-2pc7w5rx.png")}.b{background:url("./a(b)-6mem28ww.png")}.--productionimplies--minify, and aBun.serveHTML route withdevelopment: falseminifies by default, so both print the same. In@font-face, bundlingsrc:url(./Brand Fonts/inter-c07y9h2q.woff2)again gives@font-face{font-family:I}with exit code 0 and no message.Repro, quoted form (no minify needed). The stylesheet says
url("icons/logo.png").node_modules/icons/package.jsonhas"exports": {"./logo.png": "./x\");}body{color:red}a{b:url(\"y.png"}and a 128 KB file of that name:publicPath: '");}body{color:red}a{b:url("'now printsurl("\");}body{color:red}a{b:url(\"plain-w49ecq2a.png"). esbuild 0.28 prints both inputs raw.What is copied over the placeholder. The whole output path (
[dir],[name],[ext]and any literal text ofnaming.asset) andpublicPath.--asset-naming '[dir]/[name]-[hash].[ext]'withBrand Fonts/inter.woff2printedurl(./Brand Fonts/inter-<hash>.woff2)under--minify.Reach. Only assets of 128 KB or more are copied from CSS (
COPY_THRESHOLD,src/bundler/bundled_ast.rs). Smaller ones are inlined asdata:even with thefileloader, which hides the bug. #28923 removes that threshold forfile-mapped extensions.Why a placeholder.
process_files_to_copyfixes the asset's output path beforelink(). The printer still writes a placeholder (the asset's unique key) because the text to print ispublicPathplus a path relative to the chunk, and the chunk's own path is known only after its output is hashed.break_output_into_piecessplits the output at each key, andIntermediateOutput::code_with_source_map_shiftswrites the final text between the pieces. The escape is at that join because it is the one place that sees every printer's placeholder and thepublicPath.The join. It has two passes: one sums the output length, one writes. Both now call
spliced_path_partsandwrite_spliced_path, so they size and write the same bytes.SpliceEscape::for_chunkis an exhaustive match on the chunk kind. The metafile is built through the same join with a stand-in chunk, so it calls the newcode_for_metafile, which passesSpliceEscape::Rawand keeps the metafile bytes as they are on main. The enum name and the helper names are the ones open #38666 uses, so #34188, #38666 and #41793 can add arms. All four PRs edit the same two loops, and the second to land has to rebase.Cost for other chunks. None added. The shared helper normalizes the path into the growable buffer that main uses since #46021: one copy per placeholder in each pass, as on main.
Printers that write a placeholder.
Url::to_cssand theurl()token in a custom property chose the unquoted form.image-set()reachesUrl::to_cssfor the-webkit-image-setcopy that bun adds for its default targets, so it printed unquoted too. The unprefixedimage-set()and css-modulescomposesalready print a quoted string.Still wrong after this PR.
#,?,%, a tab, a line break or a trailing space does not load in a browser: the URL parser cuts at#and?and removes tabs and line breaks. That needs percent-encoding of the path on output and percent-decoding ofurl()on input, both in one change. It is handed off as separate work and is not part of this PR.Bun.serveproduction route answers 404 for an asset with a space in its name until bundler(html): percent-encode output paths written into src and href, and serve them under that name #41793 registers the encoded route.no test proof · iteration 3 · platform-specific test(s) that do not run on this machine, deferring to CI, which covers all platforms: test/bundler/esbuild/css.test.ts