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With the inspector on, the runtime transpiler appended `//# sourceURL=<module path>` after the inline source map comment, with the path bytes written raw. A line feed or a carriage return in the path ended the comment, and the rest of the path ran as code in that module. The source provider already carries the same path as its sourceURL(), and every reader of the directive falls back to it. JSC already discards the directive when the path has a space or a quote. For a non-ASCII path the directive was the UTF-8 bytes read as Latin-1, so stack traces showed a mangled path and a position that was not remapped. The debugger matches a breakpoint set by URL against the directive when there is one, so a breakpoint in a module under a non-ASCII directory never bound (#15035). It binds now.
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Status Reproduced on 1.4.3-canary.1+b99371011 (linux-x64): The breakpoint test is the case from #15035: Self-reviewed. Two things came out of it and both are in:
One more item from the self-review was lost before I could read it, so it is not addressed. If it shows up in CI or in review, I will handle it then. Overlap: #33866 drops the same lines as a side effect, and #40383 rewrites this function and keeps the raw write. Whichever lands second leaves the two appended slices out. The new tests fail if the write comes back. Review: CodeRabbit asked for The automated code review found no bugs. It asks a maintainer who knows the debugger tooling to confirm removal over escaping. The evidence for that choice is in the Notes block of the PR body: the list of every reader of the directive with its fallback, and the two alternatives considered. |
WalkthroughChangesInline sourcemap debugging
Suggested reviewers: Priority: ➖ Normal Severity of issue fixed: Medium Merge Risk: ⚪ Minimal · up to No functional debugger regression is established. The parameterized test should be aligned with the repository’s required test convention. 🚥 Pre-merge checks | ✅ 4✅ Passed checks (4 passed)
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In `@test/cli/inspect/inspect-inline-sourcemap.test.ts`:
- Around line 109-112: Replace the parameterized test declaration around the
inspect sourcemap cases with a describe.each block containing the LF and CR
inputs, then define the test inside it without parameterization. Keep isWindows
as the skip condition on the nested test and preserve the existing assertions
and test behavior.
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I reviewed this PR and didn't find any bugs. Because it fixes a code-injection path and changes inspector-visible output (dropping the sourceURL directive from Debugger.scriptParsed), a human familiar with the debugger tooling should confirm the removal-over-escaping call.
What was reviewed
on_source_map_chunkcapacity math:grow_if_needed(encode_len + prefix_len + 2)still covers the leading\n+ prefix + base64; the trailing\nuses fallibleappend, so noappend_assume_capacityoverrun.- New
inspect()helper: socket error/close and inspectee exit all reject the raced promise;disposeruns on both the setup-failure path and viaawait using; existing test's assertions are unchanged. - Tests follow harness conventions —
127.0.0.1:0,tempDir/using,Promise.allpipe draining,test.concurrent, combined{ stdout, exitCode }assertions, Windows skip narrowly scoped to the LF/CR filename cases with a stated reason.
Extended reasoning...
Overview
The Rust change removes the //# sourceURL=<path> trailer that SourceMapHandlerGetter::on_source_map_chunk appends to every transpiled module when the inspector is enabled. The path was written as raw bytes into a single-line comment, so an LF or CR in the module's absolute path terminated the comment and executed the remainder as code; non-ASCII paths were also mangled (UTF-8 bytes read as Latin-1), which broke Debugger.setBreakpointByUrl matching (#15035). The prefix_len reservation is shrunk to match, and the two append_assume_capacity calls for the sourceURL trailer are deleted. The test file gains a reusable inspect() helper (refactor of the existing test's plumbing) plus three new tests: LF/CR injection (ESM + CJS), non-ASCII stack-frame path/position, and the #15035 breakpoint-by-URL regression.
Security risks
The change removes an injection surface — raw path bytes are no longer written into program text on this path. I checked that no new user-controlled bytes are introduced into the printed output; only the base64 sourcemap and fixed literals remain. The residual risk is behavioral: dropping the sourceURL directive changes what Debugger.scriptParsed reports (the sourceURL param disappears). The PR argues every reader falls back to the provider's sourceURL()/url, and JSC already discards the directive for paths containing whitespace or quotes, so many users run without it today — but I did not independently trace every debugger-frontend consumer.
Level of scrutiny
Medium-high. The native diff is mechanically trivial and the capacity/append_assume_capacity invariant is preserved (over-reservation only, never under). But this is a security fix whose correctness depends on the design claim that the directive is fully redundant across all inspector consumers (JSC breakpoint matching, Zig::sourceURL stack frames, sampling profiler, CDP shim, VS Code adapter, Web Inspector UI). That enumeration is well-researched in the PR body, and the new tests exercise stack frames and breakpoint binding directly, but a maintainer who owns the debugger integration should sign off on remove-vs-escape.
Other factors
Test quality is strong: failure events are wired to reject awaited promises (no sleeps), resources are released via using/await using registered before assertions, subprocess pipes are drained concurrently, test.concurrent is used for independent spawns, the Windows skip is scoped to the two cases where the OS forbids LF/CR in filenames, and the variant matrix covers ESM + CJS × LF + CR. The refactor of the existing test preserves its assertions verbatim. No CODEOWNERS entry covers the changed paths. Bug-hunt exit reason was dry_streak with no findings.
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Fixes #15035
Problem
bun --inspect, a LF or a CR in a module's absolute path runs the rest of the path as code. Importinga\nglobalThis.INJECTED='ran';var y={js:1};y.jssetsglobalThis.INJECTED, throughimportandrequire.on_source_map_chunk(src/jsc/VirtualMachine.rs:3365). It appends//# sourceURL=<source.path.text>to each transpiled module and writes the path bytes raw. The line break ends the//comment.españolbecomesespañol). A breakpoint set by URL then never binds (Problems with debugging Bun in VScode: UTF-8 unicode folders with the letter "Ñ" cause errors in breakpoints. #15035), anderror.stackshows the mangled path and an unmapped position.Fix
//# sourceURL=comment. The inline//# sourceMappingURL=comment stays. @alii named this option in a review of #33866.path.textas itssourceURL()at all three call sites, and every reader of the directive falls back to it.test/cli/inspect/inspect-inline-sourcemap.test.ts(four new tests fail on 1.4.3). Also all oftest/cli/inspect/,test/js/node/inspector/, andtest/regression/issue/28159.test.ts. Other raw path writes: Macro import fails when the path of the macro file has an apostrophe #42704, bundler: percent-encode the sourceMappingURL comment #42670 (see Notes).Background
//# sourceURL=is a comment that names a script. JSC stores its value on the source provider assourceURLDirective().Zig::SourceProvider) is the JSC object that holds one module's source text and its ownsourceURL().Notes
Not fixed here.
This is not the last place where path bytes are written raw into program text. The others need an escape, not a removal, so they are separate changes:
MacroEntryPoint::generate(src/bundler/entry_points.rs:244-273) writes the macro path into a single-quotedimport('...'). An apostrophe in the path breaks the macro import. Filed as Macro import fails when the path of the macro file has an apostrophe #42704.bun build --sourcemap=linkedfooter writes the file name raw after//# sourceMappingURL=. bundler: percent-encode the sourceMappingURL comment #42670 is open for it.url()), bundler(html): percent-encode output paths written into src and href, and serve them under that name #41793 (HTMLsrcandhref).What
Debugger.scriptParsedanderror.stackreport, before and after (linux-x64,--inspect-wait=127.0.0.1:0, release 1.4.3 against this branch):sourceURLparamplainurlsourceURLparam, same framewith space,it's,a<U+00A0>bsub-é-中sub-é-ä¸U+2028 and U+2029 do not end the comment today, because the UTF-8 bytes are read as three Latin-1 characters. Only LF and CR do. A Windows file name cannot contain either, so the two line break tests skip on Windows. The two non-ASCII tests run on every platform.
Why the directive is redundant.
ResolvedSource.source_urlis built frompath.textnext to each print call:src/runtime/jsc_hooks.rs:3277,src/jsc/RuntimeTranspilerStore.rs:534,src/jsc/AsyncModule.rs:1212.Zig::SourceProvider::create(src/jsc/bindings/ZigSourceProvider.cpp:79) passes it to JSC as the provider'ssourceURL().Readers of the directive, all with a fallback to the provider URL:
InspectorDebuggerAgent::didParseSource:hasSourceURL ? script.sourceURL : script.urlfor breakpoints.scriptParsedalways sendsurl.Zig::sourceURL(src/jsc/bindings/ErrorStackTrace.cpp:364): directive, thensourceURL(), then theSourceOrigin.src/jsc/bindings/JSInspectorProfiler.cpp:130: coverageurl.SamplingProfiler.cpp:964and:1172.src/js/internal/inspector/cdp.ts:567:params.sourceURL || params.url.Models/Script.js:contentIdentifier,displayName, anddisplayURLall readurlfirst.packages/bun-debug-adapter-protocolreads onlyurlandsourceMapURL.BUN_INSPECT_CONNECT_TOmode writes no trailer at all (SourceMapHandlerGetter::get), and that debugger works fromurlalone.JSC's directive parser (
Source/JavaScriptCore/parser/Lexer.cpp,parseCommentDirectiveValue): the value stops at whitespace (0x09 to 0x0D, 0x20, 0xA0),", or'. If anything but a line terminator follows, the directive is a null string.Loaders that reach this printer path:
js,jsx,ts,tsx,text, andmd.json,jsonc,toml,yaml,json5return an object without a print, which is why a.jsonimport does not reproduce.History. #4213 added the directive together with the inline source map, with a
TODO: do we need to %-encode the path?comment and no stated reason.Overlap with open PRs.
inline_trailerbuffer and keeps the raw write ofsource.path.text. It conflicts textually with this change. The resolution is to leave the two appended slices out. The new tests fail if they come back.Alternatives considered.
Zig::sourceURL(src/jsc/bindings/ErrorStackTrace.cpp:370) returns the directive ahead of the real path, soerror.stackand the inspector would show the encoded path for every path with a space or a non-ASCII character.Test file. The existing test's socket setup moved into an
inspect()helper so the breakpoint test can share it. The assertions of the existing test are unchanged.Local run note.
compile-bytecode-tooling.test.ts"heap snapshots label never-called bytecode-cached functions" exceeds the 5 s default under the debug ASAN build and passes in 9.5 s with a longer timeout. It does not enable the inspector.no test proof · iteration 0 · platform-specific test(s) that do not run on this machine, deferring to CI, which covers all platforms: test/cli/inspect/inspect-inline-sourcemap.test.ts