error printer: keep parsing error.stack past frames without a function name - #38308
error printer: keep parsing error.stack past frames without a function name#38308robobun wants to merge 4 commits into
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…n name
Once error.stack has been materialized, fromErrorInstance rebuilds the
frames by parsing that string. A frame with no function name is printed
as a bare location (" at /path/file.js:4:7"), which is how module
top-level code and native frames look. parseFrame only accepted such a
line when it was exactly "unknown" and otherwise stopped parsing the
whole trace there, so Bun.inspect(), console.error() and the uncaught
exception printout lost that frame and every frame below it.
Decide the shape of a frame by whether it ends with ")" instead: lines
that do are "name (location)", everything else is a bare location with
an empty function name (optionally prefixed with "async ", as V8 prints
async module code). This also parses bare locations whose path contains
parentheses correctly, and tolerates trailing whitespace or "\r".
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Updated 10:05 PM PT - Aug 13th, 2026
❌ @robobun, your commit 2c45f1d has 1 failures in
🧪 To try this PR locally: bunx bun-pr 38308That installs a local version of the PR into your bun-38308 --bun |
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WalkthroughChangesThe stack-frame parser now accepts trimmed bare locations, async module frames, and parenthesized function names. Error inspection tests update snapshots and validate unnamed, URL-based, parenthesized, CRLF, serialized, and uncaught stack outputs. Stack frame inspection
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Inline comments:
In `@src/jsc/bindings/ZigException.cpp`:
- Around line 297-302: Update the frame parsing logic around the named-frame
handling in src/jsc/bindings/ZigException.cpp lines 297-302 to split at the
outer " (" delimiter, while preserving supported functionless
parenthesized-frame parsing. Add coverage in
test/js/bun/util/inspect-error.test.js lines 237-241 for `at thrower
(/fake/app/(group)/page.js:5:3)` and assert the frame is preserved exactly.
Apply the same fix in `@test/js/bun/util/inspect-error.test.js` around lines 237 -
241: Add coverage for a named frame with parentheses in its location.
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src/jsc/bindings/ZigException.cpptest/js/bun/util/inspect-error.test.js
…sing error.stack
Splitting "name (location)" at the last "(" broke named frames whose path
contains parentheses, such as "at render (/app/(group)/page.js:5:3)".
Walk back from the final ")" and split at the "(" that balances it.
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Not a duplicate of either, though both overlap with one half of this change (this is also noted in the description):
This PR is the standalone fix for the truncation plus the balancing split that the review asked for. If either of the other two lands first, the matching half of this diff becomes a trivial conflict to drop, and the other way around. |
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LGTM — the parser rewrite is small, hand-verifiable, and strictly widens what parseFrame accepts.
Reviewed: traced locationOpeningParenthesis and the new split for named frames, bare locations, (group) paths, function names with parentheses, unknown/native, async prefix, CRLF, and the empty/no-( degenerate cases — all bounds-safe on StringView and every previously-accepted line splits the same way. Confirmed frame.isAsync is already forwarded to ZigStackFrame.is_async in the existing forEachFrame callback. The normalizeError regex update and snapshot line-number shifts are mechanical. All bot feedback (CodeRabbit's parenthesized-path case, comment-cop) is resolved in the current diff.
Extended reasoning...
Overview
Two files: src/jsc/bindings/ZigException.cpp rewrites ~35 lines of V8StackTraceIterator::parseFrame (the string parser that turns error.stack back into ZigStackFrames once JSC has dropped the structured frames), and test/js/bun/util/inspect-error.test.js adds a 5-test describe block plus mechanical snapshot updates for the new import line and a fix to the debug-only normalizeError filter.
The parser change: (1) trims each line so trailing \r/space doesn't affect shape detection; (2) decides named vs. bare by whether the line ends with ); (3) for named frames, splits at the ( that balances the final ) (new locationOpeningParenthesis helper) instead of reverseFind('('); (4) for bare frames, feeds the whole line to the existing url[:line[:column]] parser instead of terminating the whole trace; (5) strips a leading async on bare frames into isAsync.
Security risks
None. Pure string parsing over a WTF::String held by the caller; all operations are non-owning StringView slices with correct bounds (the reverse loop for (unsigned i = line.length(); i-- > 0;) visits length-1..0 inclusive, and StringView_slice(line, open+1, line.length()-1) is only reached when line ends with ) so open <= length-2). No allocation, no GC, no exception scope, no user-controlled indexing.
Level of scrutiny
Moderate. This feeds every consumer of re-parsed stack frames (Bun.inspect, console.error, the uncaught-exception printer, test reporters), so a mis-parse would be visible everywhere — but the failure mode is a mis-printed frame, not a crash or memory error. I hand-traced the new logic against ~15 input shapes (named, bare, (group) in path/name, unknown, native, async , CRLF, foo) with no (, openingParentheses == 0, empty-after-trim) and every previously-accepted name (location) line splits identically (for those the last ( is the balancing one), while previously-rejected lines are now parsed instead of truncating the trace.
Other factors
- Tests are thorough: bare frames mid-stack and at the end, node's
file:///async file:///node:shapes, parentheses in path and in function name, CRLF, and an end-to-end subprocess test asserting.stack,Bun.inspectand the uncaught printout all show the same four frames. The description says all five fail on release/main and pass here. - All prior review feedback is resolved: CodeRabbit's
(group)-path finding was fixed in e33cc12 with test coverage; the comment-cop long-comment warnings were addressed in d4dd4e9/2c45f1d. - The overlap with open PRs #36602 and #35175 is documented in the description as a small textual rebase whichever lands second — a merge-order question, not a correctness one.
frame.isAsyncis already wired through tocurrent.is_asyncin the existingforEachFramecallback (line 624), so the new bare-asynchandling reaches consumers.- The bug-hunting system found nothing.
1 participant
Problem
After
error.stackhas been read (or assigned),Bun.inspect(err),console.error(err), the uncaught exception printout and thebun testfailure output stop at the first frame that has no function name. For an error thrown from a module's top-level code that is the module frame itself, so the printed trace ends one frame early; when the module was loaded byrequire(), every frame below it (the caller ofrequire()and up) is lost as well. Before.stackis read, the same error prints all of its frames.Reproduces on 1.3.14 and on current main:
Cause: once
.stackis materialized JSC drops the structured frames, sofromErrorInstance(src/jsc/bindings/ZigException.cpp) re-parses the stack string withV8StackTraceIterator::parseFrame. Frames without a function name are printed as a bare location (at /tmp/m.js:4:7, no parentheses), andparseFrameonly accepted such a line when it was literallyunknown(Fix V8StackTraceIterator to handle frames without parentheses #23034); for anything else it setoffset = stack.length()and returned false, which ends the parse of the whole trace, not just of that line (ZigException.cpp:299-311before this change).The same code split every line at its last
(, so a path containing parentheses was mis-parsed in both shapes:at render (/app/(group)/page.js:5:3)printed asat render (/app (group)/page.js:5:3)and the bareat /app/(group)/page.js:9:1asat /app (group:1:1).Fix
parseFramedecides the shape of a line by whether it ends with). If it does not, the whole line is the location and the function name is empty (a leadingasync, which V8 prints for async module code, setsisAsync); theunknownspecial case is subsumed. If it does, the line is split at the(that balances the final)(locationOpeningParenthesis), falling back to the first(when the line has more)than(. The line is trimmed first so a trailing\ror space does not change its shape.FormatStackTraceForJS.cppappends" ("and')'only when the function name is non-empty) and V8 emit exactly these two shapes, and only the named one ends with). Balancing the final)gives the right split whenever the location and the name are themselves balanced, which covers real paths ((group)route directories,file (1).js), string-literal method names with parentheses, and V8's nestedeval at ... (...)locations; the only inputs still split differently from before are ones the old code got wrong. The location of both shapes goes through the sameurl[:line[:column]]parser as before, so Windows paths,file://URLs andnode:specifiers parse the same way in both. A frame with an empty function name and a position is printed by every consumer (print_stack_trace, the JUnit and GitHub Actions reporters) asat <location>, which is what the structured path prints for module code, so the re-parsed trace now matches the trace printed before.stackwas read.name (location)line splits exactly as before (for those, the last(is the balancing one).test/regression/issue/23022-stack-trace-iterator.test.ts(theunknowncase) still passes.test/js/bun/util/inspect-error.test.js, newdescribe("printing the frames parsed back out of error.stack"): bare frames in the middle and at the end of a Bun-format stack, node'sfile:///async file:///node:top-level frames, parentheses inside the path (named and bare) and inside a function name, CRLF, and a two-file program whose.stack,Bun.inspect()and uncaught printout must all show the same four frames of the two files (top-level frame of the required module in the middle of the trace). All five fail on the release binary and on main'ssrc/underbun bd, and pass with this change. The file'snormalizeErrorhelper is also updated: debug builds now print the builtin frame asat require (51:24)rather thanat require (:1:21), so the two minified-file tests were already failing underbun bdon main.inspect.test.js,reportError.test.ts,test/js/bun/test/stack.test.ts,error-name-preservation.test.ts,circular-error-stack*.test.ts,fix-bindings-stack-trace.test.ts,prepare-stack-trace-crash.test.ts,test/js/node/v8/capture-stack-trace.test.js,test/cli/test/bun-test.test.ts,test/js/bun/test/bun_test.test.ts,bun-test.test.ts: all pass.Background
error.stackin JSC is computed lazily:ErrorInstancekeeps the capturedJSC::StackFrames until the property is first read or written, formats them into the string, and then frees them. Bun's native error printer (remap_zig_exceptioninsrc/jsc/VirtualMachine.rs, which servesBun.inspect,console.*, uncaught exceptions and the test reporters) therefore has two sources of frames: the structured frames if they still exist, otherwise the.stackstring, whichfromErrorInstanceparses back intoZigStackFrames withV8StackTraceIterator..stackfollows): each frame is a line starting with four spaces andat, followed by eithername (url:line:column)or, when there is no name, justurl:line:column. Module top-level code, Bun's native frames (unknown,native) and node's ESM top-level frames (at file:///x.mjs:4:7,at async file:///x.mjs:4:7) all take the second form.First version of this PR
The first push only changed the bare-location handling and still split named frames at the last
(; review pointed out thatat render (/app/(group)/page.js:5:3)was therefore still mis-parsed, so the balancing split and its test were added.