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Fixes #43907 Since #33685 (in 1.4.0, 1.4.1 and 1.4.2) the CSS printer takes the ?query#fragment of a rewritten url() from the text of the specifier. A literal # or ? in a directory or file name (./C#/logo.png) resolves as written, so nothing was removed, but the printer still appended #/logo.png. Before #33685 the printer appended nothing. No user reported this. It was found while reading the code for #43854. In the directory case the asset still loads, so this is about correct output: no path segments in the shipped CSS, and CSS bytes that do not depend on the location of the checkout. The resolver now reports when its retry without the suffix is the one that found the file. The bundler copies that to the import record, and the printer appends the suffix only for such a record. In-memory files never have a suffix removed. An onResolve result has no field for a suffix, so a returned path that still ends with the suffix kept it. Every other plugin result gets the suffix back, as before. Not changed: an asset whose own output path has a literal #, ? or % still prints a URL that a browser cannot load (#43908).
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Status: ready for review. CI is green on 6a4cdd7. How I reproduced it, on Bun 1.4.2+744846f84 (Linux x64): mkdir -p "C#" && head -c 200000 /dev/zero > "C#/logo.png"
printf 'body { background: url("./C#/logo.png"); }\n' > style.css
bun build ./style.css --outdir=out && grep -o 'url([^)]*)' out/*.css
# url("./logo-68tr27nb.png#/logo.png")Bun 1.3.5 and this branch print PR: #43911. Issue: #43907. Not changed here, with trackers: #43908, #43915. |
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Included review availability: This review used your included allowance. Your plan provides up to 10 included reviews per hour; 0 remain after this review. WalkthroughCSS import resolution now tracks when a query or fragment suffix was removed. The bundler records this status for resolver and applicable plugin results. The CSS printer uses it when rewriting URLs. Tests cover literal ChangesCSS URL Suffix Resolution
Suggested reviewers: Priority: ➖ Normal Severity of issue fixed: Low Merge Risk: ⚪ Minimal · up to The reviewed paths preserve CSS URL suffix behavior, including deferred plugin resolutions. No concrete merge-blocking issue remains; merge after normal checks. 🚥 Pre-merge checks | ✅ 4✅ Passed checks (4 passed)
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Inline comments:
In `@src/bundler/bundle_v2.rs`:
- Around line 5243-5246: Carry resolved_without_url_suffix through PendingImport
when the deferred import resolution is queued, then apply it to the import
record’s RESOLVED_WITHOUT_URL_SUFFIX flag when
patch_import_record_source_indices consumes the pending entry.
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src/ast/import_record.rssrc/bundler/bundle_v2.rssrc/css/printer.rssrc/resolver/resolver.rssrc/resolver/result.rstest/bake/dev/css.test.tstest/bundler/esbuild/css.test.ts
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… PendingImport An onResolve answer writes the source index and the removed-suffix flag to the import record. When the records of the importer are not on the graph yet, the answer is parked in a PendingImport and applied by patch_import_record_source_indices. The parked form now carries the flag too, so both branches write the same two facts.
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Beyond the inline findings, I also checked whether the new resolver flag could leak through a cached result: it is inserted at src/resolver/resolver.rs:1411 after resolve_without_symlinks returns, so a later resolve of the bare stripped path never sees REMOVED_URL_SUFFIX. The --external and in-memory files paths never bind source_index, so the printer's removed_url_suffix() is not consulted for them; and the .iter().zip(..).all(..) in path_ends_with_url_suffix is a pairwise compare, not a byte search, so the byte-search source lint does not flag it.
Extended reasoning...
The change adds a resolver result flag, mirrors it onto the CSS import record through the three bundler binding sites plus a heuristic for onResolve plugin answers, and makes the CSS printer re-append a url() suffix only when that flag is set; it touches no auth, crypto, or input-parsing surface beyond the specifier slice already used on main. The two confirmed inline findings (plugin echo in a custom namespace losing the fragment, and the ?v=2 after a literal # still failing to resolve) are behavioural regressions or gaps a human should weigh, which is why this is not an approve.
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Updated 8:13 PM PT - Oct 6th, 2026
✅ @robobun, your commit 111537f9bc09833a533d1812f129cbb52dbafc84 passed in 🧪 To try this PR locally: bunx bun-pr 43911That installs a local version of the PR into your bun-43911 --bun |
…ffix, as before
The comparison of the returned path with the suffix dropped a real
fragment when a plugin hands the specifier back in its own namespace and
an onLoad supplies the bytes: url("virtual:sprites.svg#icon") lost #icon
on an inlined asset. An onResolve result cannot say what the plugin
removed, so the suffix always goes back for such a record, as on main.
Only the resolver and in-memory files report exactly.
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LGTM — commit 6a4cdd7 addresses the plugin-echo case I raised earlier by dropping the path-tail heuristic and always re-appending the suffix for plugin-answered records, and the new .b { mask: url("echo:small.svg#icon") } case in test/bundler/esbuild/css.test.ts pins it.
What was reviewed:
- Traced
RESOLVED_WITHOUT_URL_SUFFIXthrough every site that assigns a url() record'ssource_indexin src/bundler/bundle_v2.rs: the sync resolver path,resolve_import_records, the onResolve success path, and thePendingImportreplay all set it; the in-memoryfilespath (lines ~2525/2533) leaves it unset, which is intended since those match by exact key and is covered by the InMemoryFiles test. - Checked
ResultFlagsbit 4 was genuinely free (u8, bits 0-3 and 5-7 taken) andImportRecordFlags1<<20 has no other user; the resolver only inserts the bit on theSuccessarm of the retry andfinalize_resultdoes not clear flags. - Printer change is a strict narrowing: same suffix slice as before, now gated on the flag, and still only for
ImportKind::Url.
Extended reasoning...
The change adds one resolver result flag and one import-record flag so the CSS printer re-appends a ?query#fragment only when the resolver actually stripped it, touching src/resolver/resolver.rs, src/resolver/result.rs, src/ast/import_record.rs, src/css/printer.rs and four resolve sites in src/bundler/bundle_v2.rs, with seven new bundler tests and one dev-server test. It touches no security-sensitive surface. The bug hunt ran dry with no findings, the earlier red finding on the plugin path was fixed in the latest commit with a simpler unconditional rule, and I independently traced the flag through every source_index assignment site; the source diff is about 60 lines, self-contained, and not under any CODEOWNERS entry.
…url-suffix-only-when-resolver-removed-it # Conflicts: # src/ast/import_record.rs
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Merged main (bbdc5a5) into this branch.
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Fixes #43907
Problem
bun buildappends part of the file path to a rewritten CSSurl()when a directory or file name has a literal#or?:url("./C#/logo.png")becomesurl("./logo-68tr27nb.png#/logo.png").Printer::get_import_record_url(src/css/printer.rs:345) takes the suffix from the specifier text. The resolver removes the?query#fragmentonly when the specifier does not resolve as written (src/resolver/resolver.rs:1385).Fix
ResultFlags::REMOVED_URL_SUFFIXwhen its retry without the suffix found the file. The bundler copies it to the import record, and the printer appends the suffix only then.filesnever set it. A record that anonResolveplugin answers always gets its suffix back, as before.test/bundler/esbuild/css.test.ts(7 new tests) andtest/bake/dev/css.test.ts(1), all fail on main. Alsobundler_plugin,bundler_html.Background
url()orimportin a parsed file. Itsoriginal_pathkeeps the specifier as written, and the resolver replacespathwith the real path.link#directory still got#/logo.png.Downsides
#,?or%still prints a URL that a browser cannot load (bun build: a CSS url() to a copied asset is not loadable when the output path has a literal #, ? or % #43908)../C#/logo.pngthat anonResolveplugin answers still gets#/logo.png: the result has nosuffixfield.Notes
Repro (1.4.2 prints the first line, 1.3.5 and this branch print the second, esbuild 0.18.6 prints no suffix either):
Reach and history:
url()specifier has a literal#or?that is part of a directory or file name. A project that lives under aC#directory and uses relativeurl()s was never affected.url(sprites.svg#icon)keeps#icon).url("data:image/png;base64,...#/logo.png"), and the dev server printed/_bun/asset/<hash>.png#/logo.png. With an absolute specifier under aC#directory, 1.4.2 printedurl("./logo-<hash>.svg#/proj/img/logo.svg"), so the bytes and the hash of the CSS chunk depended on where the project was checked out.data:URLs, and for a literal#or?in a directory under the default asset naming. It does not make any URL loadable that was not loadable before (see bun build: a CSS url() to a copied asset is not loadable when the output path has a literal #, ? or % #43908 for the cases that a browser cannot load).Design:
url()record, and how it reports:resolve_import_recordsandrun_resolverinsrc/bundler/bundle_v2.rs(the second one is used whenonResolveplugins exist and decline) read the resolver flag. In-memoryfilesmatch by exact key and never remove anything. A record that anonResolveplugin answers always gets its suffix back, as on main, because the result has no field that says what the plugin removed. That includes a specifier that is only a suffix (url("#sprite")keeps#sprite).onLoadsupplies the bytes:url("virtual:sprites.svg#icon")lost#iconon an inlined asset. The comparison is gone, and the plugin test has that case.ImportRecord::url_suffix_startis the one place that says where the suffix starts. The resolver, the printer and the plugin path call it. The resolver keeps its own guard against an empty path, as on main.PendingImport, which carries the flag too. That branch cannot run today for a printed record: the request is dispatched insideon_parse_task_complete, the same call stores the records, and the answer is always a posted task. The carry keeps both branches in step.ResultFlags(u8) and bit 20 ofImportRecordFlags(u32). No struct grows. The printer no longer scans the specifier of eachurl()(strings::index_of_any). It tests one flag bit (3 instructions).IgnoredSuffix, set only inside its retry).removed_url_suffix()from the record once both changes are in.Tests:
css/URLLiteralHashInPathFileLoader,css/URLLiteralHashInPathDataURL,css/URLLiteralQuestionMarkInPath(not on Windows,?is not legal in a file name there),css/URLLiteralHashInPathPlugin,css/URLLiteralHashInAncestorDirectoryOfAbsoluteSpecifier,css/URLLiteralHashInSymlinkedDirectory,css/URLLiteralHashInPathInMemoryFiles, and the dev server test "asset under a directory with a literal # referenced in css" (fetch only, no browser). The threecss/URLQueryFragmentPreserved*tests from css: preserve url() query/fragment suffix when rewriting asset references #33685 pass before and after.test/bake/dev/css.test.ts,metafile,bundler_files,standalone,bundler_loader,css-modules,test/js/bun/css/css.test.ts, thebyte-search,comment-copanddead-code-escapessource lints, andcargo clippyforbun_ast,bun_resolver,bun_css,bun_bundler.size build/release/bunfor release builds of the merge base (73df7bb) and of this branch: text 80,676,462 to 80,676,974 bytes, data and bss the same. The file size is the same (80,844,320 bytes). The instruction count is fromcargo rustc --release -- --emit asmof the samebitflagsoperations on a struct with the size ofImportRecord.Self-review, 8 concerns:
url("#sprite")orurl("?theme=dark")lost the suffix that 1.4.2 keeps, because the "not at index 0" guard had moved into the shared function. The guard is back in the resolver only, and the plugin test pins both cases.Found on the way, not changed here:
url("./C#/logo.png?v=2")fails withCould not resolve, tracked in bun build: url("./C#/logo.png?v=2") does not resolve when a directory name has a literal # and the URL has a query #43915. The retry cuts at the first?or#only, as in esbuild.--external "*.svg"does not apply tourl("./sprites.svg#icon"). The pattern is checked on the full specifier, before the suffix is removed.files,url("./sprites.svg#icon")does not resolve at all.onResolveplugin getsargs.kind === "internal"for aurl()record. bundler: label conditional CSS @import records as import-rule #38549 has the change for that.no test proof · iteration 1 · platform-specific test(s) that do not run on this machine, deferring to CI, which covers all platforms: test/bundler/esbuild/css.test.ts