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Status: closed. #45677 fixed this case on main. How I reproduced it (bun 1.4.3, Linux x64): the steps of #44325 with
The reason for the close is in #44396 (comment). |
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Updated 7:05 PM PT - Oct 19th, 2026
❌ @robobun, your commit 08ae139 has some failures in 🧪 To try this PR locally: bunx bun-pr 44396That installs a local version of the PR into your bun-44396 --bun |
…its source text A `// @bun` file with a JSON source map made the coverage report size its line sets for 2^31 lines: `parse_json` passed `i32::MAX` as the line count of the original, and the report allocated by it. `parse_json` now records how much text `sourcesContent` carries. The report makes room for one past the largest line that a mapping names, and for no more lines than that text can have. For a source with no text in the map, the line ends of its file are counted. `ParsedSourceMap::input_line_count` and the count parameter of `mapping::parse` are removed. Fixes #44325
…dows On Windows the flag opens the file for overlapped I/O, and the read that counts line ends is synchronous, so it failed. The flag is for a FIFO, which is a POSIX case.
Drop the count of line ends in a source file. A map in which a source has no text keeps the largest line that its mappings name.
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No actionable comments were generated in the recent review. 🎉 ℹ️ Recent review info
WalkthroughSource-map parsing no longer stores an input-line count from a parser argument. Parsed maps derive a bounded original-line count from mappings and, when available, source-text lengths. Coverage reporting uses this bound, with regression tests for map variants and memory usage. ChangesSource-map coverage bounds
Suggested reviewers: Priority: ⬆️ High Severity of issue fixed: Medium Merge Risk: ⚪ Minimal · up to
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| Check name | Status | Explanation |
|---|---|---|
| Linked Issues check |  |
Issue #44325 is closed and completed. It provides historical context only. No active directly linked issue supplies coding requirements for this pull request. |
| Out of Scope Changes check | |
The changes remain connected to the reported source-map coverage allocation problem. The parser signature updates remove the obsolete input-line-count argument, and the coverage code and regression te… |
| Title check | |
The title clearly and concisely describes the main change: limiting source-mapped coverage line sets using mapping and source-text bounds. |
| Description check | |
The description explains the problem, implementation, trade-offs, and verification results in detail. It does not use the template headings exactly, but it includes the required information for what t… |
Full details: Out of Scope Changes check
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Explanation
The changes remain connected to the reported source-map coverage allocation problem. The parser signature updates remove the obsolete input-line-count argument, and the coverage code and regression tests implement and verify bounded line reporting. The reviewed diff does not demonstrate an unrelated change.
Full details: Description check
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Explanation
The description explains the problem, implementation, trade-offs, and verification results in detail. It does not use the template headings exactly, but it includes the required information for what the PR does and how it was verified.
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Inline comments:
Review comments at @test/cli/test/coverage.test.ts:
- Line 830: Update both parameterized groups in the sourcemap coverage tests to
use describe.each() with a nested test() instead of test.each(), preserving the
existing cases and assertions.
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📒 Files selected for processing (9)
src/runtime/bake/dev_server/source_map_store.rssrc/runtime/cli/pm_diff_normalize.rssrc/sourcemap/Mapping.rssrc/sourcemap/ParsedSourceMap.rssrc/sourcemap/lib.rssrc/sourcemap_jsc/CodeCoverage.rssrc/sourcemap_jsc/JSSourceMap.rssrc/standalone_graph/StandaloneModuleGraph.rstest/cli/test/coverage.test.ts
💤 Files with no reviewable changes (4)
- src/runtime/cli/pm_diff_normalize.rs
- src/sourcemap_jsc/JSSourceMap.rs
- src/runtime/bake/dev_server/source_map_store.rs
- src/sourcemap/Mapping.rs
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Nothing blocking. The comments below are optional suggestions. There is no need to push a fix for them before merging.
Additional findings (outside the current diff — GitHub can't attach inline comments there):
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src/sourcemap_jsc/CodeCoverage.rs— Users runningbun test --coveragewith coverageIgnoreSourcemaps on a file whose last line has no trailing newline and holds a never-called function get a panic instead of a report. src/sourcemap_jsc/CodeCoverage.rs:828-830 slicesline_hits_slice[min_line..end]while min_line is still u32::MAX, because LineOffsetTable::find_index returns None for every byte past the first on a final line that no newline terminates. The sourcemap branch guards this at CodeCoverage.rs:993; the branch the new RSS test exercises does not. Fix: skip the function (or clamp) when min_line == u32::MAX before indexing, mirroring the 993 guard.Why this was flagged
The no-sourcemap branch at src/sourcemap_jsc/CodeCoverage.rs:738 runs whenever
coverageIgnoreSourcemapsis set or no map is stored, and the new test in test/cli/test/coverage.test.ts drives it withcoverageIgnoreSourcemaps. LineOffsetTable::generate at src/sourcemap/LineOffsetTable.rs:295-317 appends an EOF entry only when the file ends in a newline; otherwise the last entry is the start of the last line, and find_index at LineOffsetTable.rs:121-149 returns None for any later byte on that line. For a function whose whole range lies on that line, the loop at CodeCoverage.rs:805-822 never sets min_line, so it stays u32::MAX with max_line 0. If the function did not execute, CodeCoverage.rs:829-830 computes end = 0 and evaluatesline_hits_slice[4294967295..0], which panics with a slice-index error and kills the test run. The sibling sourcemap branch has themin_line == u32::MAX && max_line == 0guard at CodeCoverage.rs:993; this branch does not. The base branch has the same lines, but the PR added a test that now exercises this path.Verification: The no-sourcemap branch runs on a source text that does not end in a newline and whose last line holds a function that never executed. src/sourcemap/LineOffsetTable.rs:295-318 adds an EOF entry only for a file ending in a newline, so find_index returns None for later bytes on the last line; min_line stays u32::MAX and src/sourcemap_jsc/CodeCoverage.rs:830 panics. The base has the same unguarded line 830.
Keep the wrapping add of the blob line count, as before this branch. Use describe.each for the two test groups, and say why the RSS bound has no branch for ASAN.
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Two points from the automated reviews that are not on a line of the diff:
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…rage-sourcemap-line-count # Conflicts: # src/runtime/cli/pm_diff_normalize.rs
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Closing. #45677 rewrote the coverage report. It removed The case of #44325 is fixed on main. Peak RSS of
This PR also dropped a mapping whose line is past the end of its |
Fixes #44325
Problem
bun test --coveragetakes 816 MB for one file built withbun build --target=bun --sourcemap, and 512 MB more for each further file. Under--parallelthe worker stops withmemory allocation of 9126805546 bytes failed. The run prints no table and exits 0.parse_json(src/sourcemap/lib.rs:947) passedi32::MAXas the line count, and the report (src/sourcemap_jsc/CodeCoverage.rs:843) made room for 2^31 lines.Fix
ParsedSourceMap::original_line_bound()replaces the count. For a JSON map it is one past the largest line that a mapping names, capped at one past the bytes of the longestsourcesContententry.input_line_countand the count parameter ofmapping::parseare removed.test/cli/test/coverage.test.ts(13 new tests, main fails). Self-reviewed: 36 concerns raised, 26 addressed (Notes).Background
// @bunfile runs as it is, with a JSON source map. A transpiled file has a blob that stores its line count.AA+/////DA) names line 2^31. Considered reading the source file of a map without text: too much code for a hand-made input.Downsides
sourcesContententry has no cap: one mapping to line 2^31 still takes 816 MB.bun buildwrites no such map.parse_jsonruns 14 more instructions per source, and the report of a transpiled file 8 more. No allocation, no struct growth, same.textsize.Notes
The issue. #44325 is closed as not planned: automated testing found the problem, and no user ran into it. Its repro is below.
Repro (from the issue):
The bound.
namedis one past the largest original line in the mappings, and 0 for a map with no mappings.min(named, n + 1), wherenis the byte length of the longestsourcesContententry. A text ofnbytes has at mostn + 1lines.named.The report drops a mapping to a line at or past the bound. It did this before, for
line >= line_count. So the text in the map is the authority for how many lines a source has, as in Node's coverage. A map with a stand-in text that is shorter than the source loses the lines past that text. The repro gets 5 lines (its text has 81 bytes), with the same row (dist/lib.js | 50.00 | 75.00 | 4) and the same lcov record.parse_jsonalready holds eachsourcesContententry as a string, so the cap needs no pass over the text.Measured. Release builds of main bbdc5a5 and of this branch at 6f5267e, Linux x64. Peak RSS is
ru_maxrssof thebun testprocess from a small parent, the largest of 5 runs. The container has no valgrind, strace or perf. Instruction counts are fromobjdump -dof the two builds. Allocator counts are from gdb breakpoints on the entry points of mimalloc.--sourcemap=linked,inlineorexternal[null]map.tsfile that bun transpiles--parallelworker sends, the reprobun test --coverage --parallel=2, the reprodist/lib.js | 50.00 | 75.00 | 4parse_json, instructions in the loop for one sourceparse_json: the repro map, 100 sources, a[null]map.text, bytesparse_json, bytesmapping::parse, bytesReport::generate, bytespm_diff_normalize::print_js, bytessize_of::<ParsedSourceMap>()The branch has since merged main at 0b2d346. The one conflict was in
pm_diff_normalize::print_js: #45307 changed how it computes the line count that it passed tomapping::parse. The two sizes ofprint_jsin the table are from before that change.Self-review. Of the review I have the verdict and the first line of each of the 36 concerns, not the full text. The verdict: keep the bound from
sourcesContentand the removal of the stored count, and drop the count of lines from a source file. The first version of this PR read the file thatsourcesnames when a source had no text, and reported the lines of the built file with a warning when it could not. That is gone: 12 concerns were about it. 14 concerns ask for no change. These 10 are not addressed:bun test --parallelexits 0 after a worker died, so a threshold can pass (2 concerns). That is a separate bug.parse_jsonstill passesi32::MAXas the source count tomapping::parse. A real count rejects a map whose mappings name a source past the list, which changes stack traces.bun buildoutputs the tests cover. Its first line does not say which output is missing.bun build --compile(next list).Not changed here.
internal_source_map::from_vlq(src/sourcemap/InternalSourceMap.rs:1254) writes largest line + 1 into the blob header.bun build --compileuses it.src/sourcemap/Chunk.rs:466).Open PRs. #38282, #41528 and #36603 read
input_line_count + 1in the report and must calloriginal_line_bound()after this. #44363 edits the samemapping::parsecall inparse_json. With #36582 an absent or shortsourcesContentcounts as a source with no text.Suites on the debug build, after the merge of main:
coverage.test.ts(45 pass),bun-pm-diff.test.ts(74 pass, 1 skip),inspector-profiler.test.ts,test/js/bun/sourcemap/, the three source map files oftest/js/node/module/,test/regression/issue/10139.test.ts, the two source map files oftest/bake/dev/and the two oftest/bundler/. Before the merge:parallel.test.ts(43 pass, and 2 tests of worker scaling fail on the debug build), andcargo checkofbun_sourcemapandbun_sourcemap_jscforx86_64-pc-windows-msvcandaarch64-apple-darwin.[human-review] gate passed · iteration 1 · 9 files touched
fails on main (without fix)
passes on PR (with fix)
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gate history · 1 passed · 0 rejected · iteration 1
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