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bun test --coverage: append a final newline to a text that lacks one - #44295

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@robobun robobun commented Sep 30, 2026 •

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Problem

  • bun test --coverage aborts after the tests pass: panic: range start index 4294967295 out of range for slice of length 5.
  • The file starts with // @bun and has no final newline. A never-run function starts and ends on its last line.
  • Cause: find_index (src/sourcemap/LineOffsetTable.rs:121) gives an offset a line only with a later row in the line table. Without the abort, the report omits that line.

Fix

  • Under bun test --coverage, Zig::SourceProvider::create appends a newline to such a text. The report is then that of the text plus a newline.
  • In generate_report_from_blocks (src/sourcemap_jsc/CodeCoverage.rs), the loop for a never-run function writes per line. It no longer slices with line numbers (a second abort, Notes).
  • Verified: test/cli/test/coverage.test.ts (15 new tests, main aborts), inspector-profiler.test.ts, vitest.test.ts.
  • Self-reviewed: 17 concerns raised, 14 addressed, 3 did not hold.

Background

  • JSC reports coverage as ranges of text offsets. A table of line starts gives each offset a line.
  • A // @bun file runs as written. bun's printer ends other texts with a newline.
  • create makes the source of each user module. An earlier push changed the report instead: a last line of }; still had no record.

Downsides

  • Such a file now reports its last line, so a coverageThreshold that it passed can fail.
  • Under bun test --coverage, such a text is one unit longer than the file. A syntax error at its end is one line later.
  • create, per module load: +2 instructions with coverage off, +16 with it on. Such a text: one more allocation and copy. Text segment: +256 bytes.
Notes

Nobody reported this. I found it by a read of the report code during other work. There is no issue.

Repro (the file has no newline at the end):

printf '// @bun\nexport function first() {\n  return 1;\n}\nexport const second = () => 2;' > prebuilt.js
printf 'import { expect, test } from "bun:test";\nimport { first } from "./prebuilt.js";\ntest("a", () => { expect(first()).toBe(1); });\n' > a.test.ts
bun test --coverage

bun 1.3.0 crashes on it too (segmentation fault), so this is not a regression.

Which texts.

  • has_bun_pragma (src/js_parser/parse/parse_entry.rs) is a prefix test. A first line such as // @bundled by a tool matches, also after a hashbang line, also in a .ts file.
  • Under a changed Module.wrapper, JSCommonJSModule::evaluate builds the text as wrapper start, printed module, wrapper end. That text ends where the wrapper end does.
  • The printed module has a source map. So bun test --coverage reads that text through the map and does not abort on main. It aborts with coverageIgnoreSourcemaps = true.
  • A plugin can give such a text to bun from onLoad.
  • The function does not have to be alone on the last line. export const first = () => 1; export const second = () => 2; as the last line aborts too.

Why the text and not the report. JSC ends the last block of a program on the last unit of the text. The report does not count the last unit of a range. With a final newline that unit is the newline. Without one it is the last unit of the code. The report cannot tell which range is the last block of the program, because JSC gives the ranges with no owner. An earlier push of this PR worked on the ranges. Its last line had one hit less for each range that ended there. A review comment on this PR suggested the newline.

The change in create.

  • The newline goes to a text that has a line terminator and does not end with one. The test is JSC::isLineTerminator, so a text that ends with CR runs as it is.
  • A text of one line stays as it is. bun runs an empty .cjs file as (function(){}), and that file reports no line.
  • The two Module.wrapper paths of JSCommonJSModule.cpp, the // @bun paths and plugin contents all reach create. No producer changes.
  • InternalModuleRegistry.cpp registers the text of a builtin module without create, in debug builds. Those texts end with a newline.

The gate. The newline goes only to a process that writes the report of bun test --coverage (BunTest__writesCoverageReport). A process that turns the profiler on with node:inspector runs the text as it is. Profiler.takePreciseCoverage then ends the script at 78 for the repro file, as node does. In such a process, codeCoverageForFile of bun:jsc omits the last line as on main, and does not abort. A wider gate is one condition less in create: each text that the profiler covers. It makes that hook exact too, and moves the script end to 79.

The second abort. On main the same slice aborts for this text, which ends with a newline: "// @bun\n// \u00a9\u00a9\n\n\n\n\n()=>1;\nexport const first = () => 1;\n". JSC counts such a text in bytes. The table counts its UTF-8 form, which has four bytes more before line 7. So each offset of the never-run function on line 7 is the start of a blank line in the table. The report gives the start of a line to no line, and the line numbers of the function stay unset. The per-line write does nothing then. The test a function that never ran and that the line table puts on no line covers this. #38710 changes the unit of the table.

Measured, release builds of main 2722608 and this branch in one directory:

main this PR
152 cases with no final newline: aborts 29 0
lcov record and table row equal to those of the text plus a newline 20 152
text segment, bytes 80,675,723 80,675,979
Zig::SourceProvider::create, bytes 1,906 2,334
instructions in create per module load, coverage off 138 140
the same, coverage on, a module that bun prints 202 218
the same, coverage on, a // @bun text of 10,000 bytes with no final newline 214 341
calls from create for that text 11 14
line of a syntax error at the end of a text of 3 lines, under bun test --coverage 3 4
Profiler.takePreciseCoverage with only node:inspector, end of the script for the repro file of 78 bytes 78 78
bytecode cache hits for bun build --bytecode output under --coverage 0 0
  • The 152 cases are 75 texts in 76 files. Each runs with a test that calls first() and with a test that calls every export. They are local and not in the repository.
  • For texts that end with a line terminator, 462 lcov records are byte-identical between the two builds. They are 77 files, with a source map, without one, and with coverageIgnoreSourcemaps, serial and with --parallel=2.
  • Instructions are nexti counts in gdb for each call of create, over 100 module loads, on the builds with symbols. The count for main is from this branch without the change in ZigSourceProvider.cpp.
  • With coverage off, the two traces differ by two register moves. No branch and no call is new.
  • The three calls more are one allocation with one copy of the text (tryMakeStringImplFromAdaptersInternal), and the release of the old string.
  • node 26.3.0 gives 78 for the end of the script. Without --coverage, the syntax error is on line 3 on both builds.

Not covered by a test. A // @bun file with a .map file beside it reads the report through the source map. There is no automated case because of #44325: that run takes 794 MB.

Two other bugs, not changed here.

Related PRs. #36603, #38282 and #41528 rewrite the report code and #38710 changes the unit of the line table. None of them is for this input. This PR changes one line of that code.

The review items that did not hold.

  • More detail on the syntax error at the end of the text. The line is the part that a user sees.
  • all-on-the-last-line.js as a copy of the first fixture. It is the text of two lines.
  • Texts that change in more cases than this description states. The review found none.

Suites. coverage.test.ts: 42 pass on the release build. On the release build of main, the new block fails with the panic. On the debug build the new block passes (15 tests). inspector-profiler.test.ts: 46 pass. vitest.test.ts: 2 pass. parallel.test.ts: 45 pass.


[human-review] gate passed · iteration 1 · 3 files touched

fails on main (without fix)
ASAN without fix: 1 FAILED
$ BUN_DEBUG_QUIET_LOGS=1 bun scripts/build.ts --profile=debug --quiet test "--reporter=junit" "--reporter-outfile=/tmp/pr_gate.xml" test/cli/test/coverage.test.ts
bun test v1.4.3 (367d939d9)

test/cli/test/coverage.test.ts:
bun test v1.4.3 (367d939d9)

demo.test.ts:
--------------|---------|---------|-------------------
File          | % Funcs | % Lines | Uncovered Line #s
--------------|---------|---------|-------------------
All files     |    0.00 |   66.67 |
 demo.test.ts |    0.00 |   66.67 | 1
--------------|---------|---------|-------------------

 0 pass
 0 fail
Ran 0 tests across 1 file. [148.00ms]
(pass) coverage crash [234.74ms]
bun test v1.4.3 (367d939d9)

demo2.ts:

 0 pass
 0 fail
Ran 0 tests across 1 file. [165.00ms]
(pass) lcov coverage reporter [231.04ms]
(pass) coverage excludes node_modules directory [306.20ms]
(pass) coveragePathIgnorePatterns - single pattern string [242.35ms]
(pass) coveragePathIgnorePatterns - partial coverage without nan [240.86ms]
(pass) coveragePathIgnorePatterns - array of patterns [371.34ms]
(pass) coveragePathIgnorePatterns - glob patterns [403.66ms]
(pass) coveragePathIgnorePatterns - lcov reporter [365.64ms]
(pass) cov
... (truncated)

release without fix: 2 FAILED
bun test v1.4.3-canary.1 (e67796c68)

test/cli/test/coverage.test.ts:
bun test v1.4.3-canary.1 (e67796c68)

demo.test.ts:

 0 pass
 0 fail
Ran 0 tests across 1 file. [3.00ms]
(pass) coverage crash [10.76ms]
bun test v1.4.3-canary.1 (e67796c68)

demo2.ts:

 0 pass
 0 fail
Ran 0 tests across 1 file. [8.00ms]
(pass) lcov coverage reporter [12.84ms]
(pass) coverage excludes node_modules directory [9.88ms]
(pass) coveragePathIgnorePatterns - single pattern string [8.26ms]
(pass) coveragePathIgnorePatterns - partial coverage without nan [6.55ms]
(pass) coveragePathIgnorePatterns - array of patterns [5.87ms]
(pass) coveragePathIgnorePatterns - glob patterns [7.44ms]
(pass) coveragePathIgnorePatterns - lcov reporter [6.52ms]
(pass) coveragePathIgnorePatterns - invalid config type [2.24ms]
(pass) coveragePathIgnorePatterns - invalid array item [2.08ms]
(pass) coveragePathIgnorePatterns - empty array [6.83ms]
(pass) coveragePathIgnorePatterns - ignore all files [6.47ms]
(pass) --parallel merges line coverage across workers [125.85ms]
(pass) --parallel merges function coverage across workers [19.95ms]
(pass) a file loaded more than once counts every load > by the host and by a
... (truncated)
passes on PR (with fix)
ASAN with fix: all passed
$ BUN_DEBUG_QUIET_LOGS=1 bun scripts/build.ts --profile=debug --quiet test "--reporter=junit" "--reporter-outfile=/tmp/pr_gate.xml" test/cli/test/coverage.test.ts
bun test v1.4.3 (367d939d9)

test/cli/test/coverage.test.ts:
bun test v1.4.3 (367d939d9)

demo.test.ts:
--------------|---------|---------|-------------------
File          | % Funcs | % Lines | Uncovered Line #s
--------------|---------|---------|-------------------
All files     |    0.00 |   66.67 |
 demo.test.ts |    0.00 |   66.67 | 1
--------------|---------|---------|-------------------

 0 pass
 0 fail
Ran 0 tests across 1 file. [146.00ms]
(pass) coverage crash [230.67ms]
bun test v1.4.3 (367d939d9)

demo2.ts:

 0 pass
 0 fail
Ran 0 tests across 1 file. [284.00ms]
(pass) lcov coverage reporter [384.59ms]
(pass) coverage excludes node_modules directory [274.19ms]
(pass) coveragePathIgnorePatterns - single pattern string [233.30ms]
(pass) coveragePathIgnorePatterns - partial coverage without nan [364.57ms]
(pass) coveragePathIgnorePatterns - array of patterns [432.74ms]
(pass) coveragePathIgnorePatterns - glob patterns [307.77ms]
(pass) coveragePathIgnorePatterns - lcov reporter [297.95ms]
(pass) cov
... (truncated)

release with fix: all passed
$ bun scripts/build.ts --profile=release
[configured] bun-profile → bun (stripped) in 2632ms (unchanged)
ninja: Entering directory `/workspace/bun/build/release'
[1/210] gen cpp.rs (cppbind)
[2/210] gen JS modules (bundle-modules)
Preprocess modules (10437ms)
Bundle modules (563ms)
Postprocesss modules (677ms)
Bundle Functions (452ms)
Generate Code (71ms)

[12.21s] Bundled "src/js" for production
  2613 kb
  198 internal modules
  13 native modules
  50 internal functions across 16 files
[3/207] build.rs build_script_build
[4/207] rustc bun_platform 
[5/207] rustc bun_core 
[6/207] rustc bun_safety 
[7/207] rustc bun_zlib_sys 
[8/207] rustc bun_boringssl_sys 
[9/207] rustc bun_output 
[10/207] rustc bun_zstd 
[11/207] rustc bun_ptr 
[12/207] rustc bun_picohttp 
[13/207] rustc bun_cares_sys 
[14/207] rustc bun_base64 
[15/207] rustc bun_brotli 
[16/207] rustc bun_errno 
[17/207] rustc bun_lsquic_sys 
[18/207] rustc bun_tcc_sys 
[19/207] rustc bun_valkey 
[20/207] rustc bun_clap 
[21/207] rustc bun_shell_parser 
warning: `feature(generic_const_exprs)` is not supported with the next-generation trait solver
 --> src/shell_parser/lib.rs:1:30
  |
1 | #![feature(adt_cons
... (truncated)
diff hotspot
src/sourcemap/LineOffsetTable.rs  |   9 ++
 src/sourcemap_jsc/CodeCoverage.rs |  43 ++++++-
 test/cli/test/coverage.test.ts    | 238 +++++++++++++++++++++++++++++++++-----
 3 files changed, 258 insertions(+), 32 deletions(-)

gate history · 1 passed · 1 rejected · iteration 1

evidence per changed file
file                               reads  edits  tests
src/sourcemap/LineOffsetTable.rs       1      1     79
src/sourcemap_jsc/CodeCoverage.rs     10      7     80
test/cli/test/coverage.test.ts         6      0     79

The report of `bun test --coverage` finds the line of each offset of a
JSC range in the table of line starts. The lookup places an offset on a
line only when the start of the next line is known. So nothing on the
last line of a text with no final newline was on a line.

A function that never ran and that is wholly on that line made the
report abort: "range start index 4294967295 out of range for slice of
length N". All other code on that line was missing from the report.

`ByteRangeMapping::compute` now appends a row for the end of such a
text, and records the length of the text. JSC ends the last block of a
program on the last unit of its text. For such a text the report gives
that block the end it has when a line terminator follows, so the text
reports what the same text plus a newline reports.

The zero-fill for a function that never ran writes each line in the
loop it already has, and no longer slices with the line numbers.
@robobun

robobun commented Sep 30, 2026 •

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Reproduced on main 2722608 (release build) and on 1.4.2, Linux x64. The file has no newline at the end:

printf '// @bun\nexport function first() {\n  return 1;\n}\nexport const second = () => 2;' > prebuilt.js
printf 'import { expect, test } from "bun:test";\nimport { first } from "./prebuilt.js";\ntest("a", () => { expect(first()).toBe(1); });\n' > a.test.ts
bun test --coverage

Result: panic: range start index 4294967295 out of range for slice of length 5, exit 134, no coverage table. With this branch the run exits 0 and prebuilt.js reports FNF:2 FNH:1 DA:2,10 DA:3,9 DA:4,1 DA:5,21 LF:4 LH:4, the same record as the file with a final newline.

PR: #44295

CI: the diff is green on every lane. The two red builds are from other causes.

  • Build 122763 ran this code (1dfc778222). 180 of 181 jobs passed. The one failure was test/js/web/workers/worker-terminate-lifetime.test.ts on darwin x64 (worker exited 3). That is a worker test with a deadline of 150 ms. This PR does not touch it.
  • Build 122810 ran the same code again (f0b37f5cc6 is an empty commit). 180 of 181 jobs passed, darwin x64 included. The one failed job is darwin any aarch64 - test-bun: buildkite-agent artifact download timed out after 120s, before a test ran. The same job passed in build 122763.
  • A retry of that one job in Buildkite is all that CI needs.

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coderabbitai Bot commented Sep 30, 2026 •

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📥 Commits

Reviewing files that changed from the base of the PR and between a0c3086 and 1dfc778.

📒 Files selected for processing (3)
  • src/jsc/bindings/ZigSourceProvider.cpp
  • src/runtime/cli/test_command.rs
  • test/cli/test/coverage.test.ts

Included review availability: This review used your included allowance. Your plan provides up to 10 included reviews per hour; 1 remain after this review.


Walkthrough

Coverage-enabled sources gain a final newline when they contain a line terminator and lack one. Coverage reporting resets unexecuted function line hits individually. Tests compare coverage results for source text with and without a final newline.

Changes

Coverage for Unterminated Source Text

Layer / File(s) Summary
Normalize coverage source endings
src/runtime/cli/test_command.rs, src/jsc/bindings/ZigSourceProvider.cpp
A C ABI function reports whether the Jest runner writes coverage. When coverage reporting is enabled, selected, non-builtin sources gain a final newline if they contain a line terminator and lack one.
Compare coverage for source variants
src/sourcemap_jsc/CodeCoverage.rs, test/cli/test/coverage.test.ts
Unexecuted function line hits are reset individually. Tests compare text and LCOV reports and codeCoverageForFile() results for terminated and unterminated text. The repeated-load tests use a shared coverage runner.

Suggested reviewers: jarred-sumner

Priority: ➖ Normal

Merge Risk: ⚪ Minimal · up to 1dfc7

No confirmed issue remains that would prevent merging the coverage fix.

🚥 Pre-merge checks | ✅ 4
✅ Passed checks (4 passed)
Check name Status Explanation
Linked Issues check ✅ Passed Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check ✅ Passed Check skipped because no linked issues were found for this pull request.
Title check ✅ Passed The title clearly summarizes the main change: appending a final newline for text processed by bun test coverage.
Description check ✅ Passed The description is detailed and covers the problem, fix, verification, scope, tradeoffs, and known limitations. It does not use the template headings exactly, but it provides the required information …

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Nothing blocking. The comments below are optional suggestions. There is no need to push a fix for them before merging.

Beyond the inline finding on the as_if_terminated block selection, I also checked the other new arithmetic and plumbing: length - 1 in as_if_terminated cannot underflow because compute only sets unterminated_length for a text with at least two lines and a non-empty last line; ByteRangeMapping::compute has a single call site, so no path constructs a mapping with a stale source_length; and ByteRangeMapping__addSourceID reuses the existing mapping, so the wrapped module._compile() load inherits the same unterminated_length. The extra end-of-text row lines up with the empty trailing row a terminated text already gets from LineOffsetTable::generate, so line_count and the lcov LF are consistent between the two forms.

Extended reasoning...

The change touches the JSC coverage converter (src/sourcemap_jsc/CodeCoverage.rs) and adds a constructor in src/sourcemap/LineOffsetTable.rs, plus a new describe block in test/cli/test/coverage.test.ts; it touches no security-sensitive surface. The block-selection heuristic in as_if_terminated has a confirmed inline finding about nested never-run functions, and the rest of the diff (bounds, OOM routing, single call site, wrapped-load reuse) checked out, so the note above only records what else was examined.

Comment thread src/sourcemap_jsc/CodeCoverage.rs Outdated
When the last block of a program starts at or after the end of the
text, JSC moves its start back onto the last unit. The block before it
then ends on the last unit, or one unit later. `as_if_terminated` now
leaves the blocks as they are when a block ends one unit after the
text, and gives the later end only to an empty range that ran.

Before, a text with no final newline that ends with a conditional whose
last arm is a function showed that function's line as run. A branch
that was not taken and that ends with a function lost its line.

The tests use one `bun test --coverage` run.
Comment thread src/sourcemap_jsc/CodeCoverage.rs Outdated
Comment thread src/sourcemap_jsc/CodeCoverage.rs Outdated
Comment thread src/sourcemap_jsc/CodeCoverage.rs Outdated

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Nothing blocking. The comments below are optional suggestions. There is no need to push a fix for them before merging.

Comment thread src/sourcemap_jsc/CodeCoverage.rs Outdated
For a text with no final newline, the report no longer extends the last
block of the program by one unit. That rule needed three guards to find
the block among the ranges that JSC reports. For `if (c)\n 0` it
reported the branch as run when the branch was not taken.

`Report::generate` makes one executed range `[length, length - 1]` of
each load empty. JSC leaves that range after a function that ends the
text. `Generator` is as it is on main.

The last unit of such a text is not counted, so its last line can have
fewer hits than with a final newline. The tests compare the functions
and the lines with the same text plus a newline, and not the hit counts.

New tests: a text that loads twice, and a text with a final newline
whose never-run function gets no line. On main the second text aborts
in the zero-fill.

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Nothing blocking. The comments below are optional suggestions. There is no need to push a fix for them before merging.

Comment thread src/sourcemap_jsc/CodeCoverage.rs Outdated
`Zig::SourceProvider::create` appends a newline to a text of two or more
lines whose last line has no terminator, when the text is registered for
coverage. JSC's ranges and the line table are then those of the same
text plus a newline, so the report is the same too.

This replaces the end row in the line table and the range rule in
`Report::generate`. The converter keeps one change: the loop for a
never-run function writes each hit count in the loop. On main the slice
in that loop also aborts for a text that ends with a newline.

The tests compare the whole lcov record of a text with the record of the
same text plus a newline.
@robobun

robobun commented Oct 1, 2026 •

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Updated 8:05 AM PT - Oct 2nd, 2026

✅ @robobun, your commit 988bba191b77e1d5fd70d73cffa688ee96151c72 passed in Build #122879! 🎉


🧪   To try this PR locally:

bunx bun-pr 44295

That installs a local version of the PR into your bun-44295 executable, so you can run:

bun-44295 --bun

@robobun robobun changed the title coverage: report the last line of a text that has no final newline coverage: give a text registered for coverage a final line terminator Oct 1, 2026

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I reviewed the latest push (the fix moved from Report::generate/compute to appending a line terminator in SourceProvider::create) and did not find bugs; because every covered module's source text now passes through this hook, a human look is still worthwhile.

What was reviewed:

  • lacksFinalLineTerminator and the makeString(string, '\n') site in src/jsc/bindings/ZigSourceProvider.cpp: gated on shouldGenerateCodeCoverage, so non-coverage runs and builtins (including standalone-graph modules, which arrive as builtins) are untouched; ByteRangeMapping__generate and GraphCommonJSSourceProvider read the modified provider->source(), so the line table and the text agree; the inline //# sourceMappingURL lookup stops at the next \n, so the appended terminator does not disturb it.
  • Two consequences of the longer text that a maintainer may want to accept explicitly: under node:inspector Profiler.startPreciseCoverage, collectPreciseCoverage reports sourceLength (src/jsc/bindings/JSInspectorProfiler.cpp:133) and the program's block end one unit past the on-disk file for such texts; and a // @ bun @ bytecode file with a .jsc sidecar and no final newline will have its cached bytecode rejected by JSC's source-key comparison under coverage and be parsed from source instead (functionally fine, just slower).
  • The Rust change in src/sourcemap_jsc/CodeCoverage.rs: line < end <= line_count == line_hits.len(), so the per-line write is in bounds, and the min_line == u32::MAX case now yields an empty loop instead of a panic; no other fill over a line range remains in the file.
Extended reasoning...

The net diff is 12 lines of C++ in SourceProvider::create (append '\n' to a covered, non-builtin text that has line terminators but no final one), a one-line Rust change replacing a slice fill with a per-line write, and ~250 lines of new tests in test/cli/test/coverage.test.ts that compare each unterminated fixture's lcov record, text row and bun:jsc row with its newline-terminated twin. It touches no security-sensitive surface. Not approving because the hook alters the source text JSC compiles for every covered module and has observable side effects beyond bun test (inspector sourceLength, sidecar bytecode rejection), and because the mechanism changed entirely since the last push so no prior human review covers it; no CODEOWNERS entry covers the changed files and no third-party objection is outstanding.

`Zig::SourceProvider::create` now asks `BunTest__writesCoverageReport`
before it appends a newline to a text. A process that turns the
profiler on with `node:inspector` runs the text as it is, as node does.
There, `codeCoverageForFile` omits the last line of such a text as on
main, and does not abort.

The test for a line terminator is `JSC::isLineTerminator`.

Tests: the block runs with `coverageIgnoreSourcemaps`, so the report of
the CommonJS file under a changed `Module.wrapper` is of the text that
ran. The plugin gives a text that the file on disk does not have. A
process with only `node:inspector` checks that the script ends where the
file ends.
@robobun robobun changed the title coverage: give a text registered for coverage a final line terminator bun test --coverage: append a final newline to a text that lacks one Oct 2, 2026
@robobun

robobun commented Oct 2, 2026

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1dfc778 answers the two consequences that the review of a0c3086 listed.

  • node:inspector: the newline now goes only to a process that writes the bun test --coverage report. A process that turns the profiler on with Profiler.startPreciseCoverage runs the text as it is. Profiler.takePreciseCoverage ends the script at 78 for the file of 78 bytes, as node 26.3.0 does. The test the text is as it is after Profiler.startPreciseCoverage covers it. With a0c3086 that test fails with 79.
  • Bytecode: under --coverage, the cached bytecode of bun build --bytecode output has 0 hits on main too (BUN_JSC_verboseDiskCache=1, the file as built and with its final newline removed). So the newline adds no miss.

The same push uses JSC::isLineTerminator in place of a local copy of that test, and makes three tests fail without the change in ZigSourceProvider.cpp that passed without it before (the Module.wrapper case, the plugin case, and the bun:jsc rows).

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I reviewed the latest push (the BunTest__writesCoverageReport gate) and didn't find any bugs. Because the fix changes the text JSC executes under bun test --coverage rather than the converter — which the description itself flags as a maintainer call (EOF syntax-error line shifts by one, Profiler.takePreciseCoverage endOffset grows by one) — a human look at that design choice is still worthwhile.

What was reviewed:

  • Gate liveness: Jest::RUNNER is set before the VM enables the profiler and cleared only on the two exit paths; --parallel workers receive --coverage on their argv, so the predicate is true there too. Outside bun test it is false, which the node:inspector test pins.
  • Terminator set: JSC::isLineTerminator (LF, CR, U+2028, U+2029) matches LineOffsetTable::generate, so a CR-terminated text is left alone on both sides.
  • The fill(0) -> per-line write in ByteRangeMapping: same min_line..max_line.min(line_count) range, only the empty-range case (min_line == u32::MAX) now no-ops instead of panicking, and it matches the source-map arm's existing loop.
  • The appended string flows into ByteRangeMapping__generate via provider->source(), so the line table and JSC offsets see the same text; m_hash still comes from the original source_code_hash, which only matters for bytecode cache hits that the profiler already disables.
Extended reasoning...

The diff adds a bun test --coverage-only branch in Zig::SourceProvider::create that appends '\n' to a multi-line source text lacking a final terminator, a new C-ABI predicate in test_command.rs, a per-line write replacing a bulk slice fill in CodeCoverage.rs, and a fixture-matrix test block in coverage.test.ts. It touches no security-sensitive surface. The change is small and the tests cover unterminated/terminated pairs, CR, empty CJS, wrapper-changed CJS, plugin text, and the inspector path, and the new commit answers my earlier inline findings. I deferred rather than approved because the fix mutates executed source text as a workaround for the converter's inability to identify the program's last block, which the PR itself raises as a maintainer decision, and the prior reviews on this PR were from this bot with no independent human sign-off.

Jarred-Sumner added a commit that referenced this pull request Oct 20, 2026
… and CLI (#46021)

### What does this PR do?

Hardening. This collects the open pull requests that fix a crash in Bun
into one change, and fixes about 20 more crashes that had no pull
request.

"Crash" here means a segfault, a Rust panic, an abort, a failed
assertion, memory corruption that a sanitizer reports, a native stack
overflow, or an exception that ends the process and that the program
can't catch. With this PR those cases throw a normal error, print a
normal CLI error and exit 1, or just work.

306 pull requests are included: 227 whole, and 79 cut down to the crash
fix where the rest was a refactor, a feature or a behavior change. Each
one was checked against current `main` first. 45 more turned out to be
fixed already, and 17 were duplicates. The full list is at the bottom.

#### Crashes you could hit in normal use

- **`bun build` with macros and a `.env` file crashed at random.** In a
repro with many macro modules, more than a third of the builds crashed.
Now 3,000 of 3,000 produce the right bundle. (#45960)
- **`bun run` and `bunx` aborted if a signal arrived while the child was
being spawned.** (#38926, #45965)
- **`bun build --compile ./index.js ./public/*` panicked** if an
embedded file's name wasn't valid UTF-8.
- **A truncated or corrupted compiled executable** died with SIGBUS or a
panic at startup. It now prints an error. (#31787, #38251, #41360)
- **Dev server:** several `Option::unwrap()` panics after a failed or
deleted import (#38046, #44744, #44746), a segfault when an `onLoad`
plugin throws while another bundle is queued, a request that hung and
then panicked with `bundle active`, and `server.stop()` that never
resolved after a client aborted a waiting request.
- **`Bun.serve`:** `server.fetch(url, { headers: new Headers() })`
followed by a GC segfaulted (#40888). Routes were used after free after
`server.reload()` with `tls.serverName` (#38636).
- **`text()` and `json()` on a stream of string chunks** could abort the
process, a regression in 1.4.0. (#44269)
- **`Bun.Transpiler` with `exports.eliminate` or `exports.replace`**
aborted on `export default 1` and on most re-export clauses. (#44137)
- **A decorated `declare` field in a class expression** with
`experimentalDecorators` panicked. (#38095)
- **YAML and JSON5 files with a key that isn't a string** panicked with
`--no-bundle` and in `Bun.Transpiler`. (#41827)
- **`Bun.FileSystemRouter`:** reading `.params` segfaulted when a
rejected route candidate left its parameters behind. (#39290, #39291)
- **Native addons that call `uv_async_*`, `uv_timer_*`, `uv_idle_*`,
`uv_prepare_*`, `uv_check_*`, `uv_queue_work` or `uv_cwd`** aborted with
"unsupported uv function" on Linux and macOS. They're implemented now.
(#36609, #39652, #39892)
- **`--watch` and `--hot`** panicked when the system was out of inotify
instances or file descriptors, or when the reload `exec` failed. They
print an error now. (#39629, #39975, #44837)
- **Paths longer than the path buffer** panicked in `bun install`, the
resolver, the bundler, `--compile`, `tsconfig.json` `paths` and
`baseUrl`, `package.json` `main` and `sideEffects`, `bun run --filter`,
`bun pm diff`, source maps and snapshots. They're ordinary errors now,
or they work. (#36340, #37529, #39104, #39650, #43067)
- **A Worker that creates a `ShadowRealm` and imports
`node:worker_threads` in it** segfaulted.
- **`structuredClone` or `postMessage` of an X25519 key** gave an object
that aborted the process when read. (#45624)
- **`node:stream` web adapters and `node:http2`** could end the process
with an exception that no handler could catch. (#45076, #45975)
- **Windows:** a watcher panic in a burst of file changes (#44344), a
segfault after the machine resumes from sleep (#33015), crashes in the
shell's pipe reader (#39638, #43606), and addons that import from
`node.exe` without the delay-load hook (#35618).

Most of the rest needs unusual input: strings near the 2 GiB limit,
buffers that another thread or a getter resizes or detaches in the
middle of a call, `worker.terminate()` at a bad moment, running out of
memory or file descriptors, very deep nesting, or hostile arguments to
`bun:ffi`, `node:vm` and `bun:sqlite`.

#### Behavior changes

Things that didn't crash before and behave differently now:

- `new` on native functions that aren't constructors throws a
`TypeError`, as in Node: `util.types.*`, `buffer.isAscii`, `isUtf8`,
`transcode`, `resolveObjectURL`, `bun:jsc` exports, `cc()` symbols. It
used to return the call's result. They also stop printing as `[class
hostname]`. (#34575)
- `` $`cmd` `` throws `ERR_INVALID_ARG_VALUE` if an environment
variable's name or value contains a NUL byte. It used to cut the value
at the NUL. (#44981)
- `cc()` functions throw a `TypeError` for arguments that used to reach
C as garbage, and `read.*(ptr, NaN)` throws. (#37989, #38057, #40773)
- As PID 1, `bun` exits with 128 + the signal number on Ctrl+C or
`docker stop`. (#38877)
- A `NODE_MODULE` addon that's already loaded by the main thread throws
`ERR_DLOPEN_FAILED` when a live Worker loads it too, as in Node.
(#39968)
- An exception from a `node:vm` context reaches `uncaughtException`
handlers. (#39992) `vm.constants.DONT_CONTEXTIFY` returns the real
global proxy. (#34623)
- `createPrivateKey` rejects an EC JWK whose private value doesn't match
its public point. (#33752)
- `@dec static {}` is a syntax error, as in TypeScript and esbuild.
(#44883)
- `clearTimeout` ignores 0 and negative ids, and timer ids no longer
wrap. (#44771)
- HEAD for a `Response` whose body is an S3-backed `Blob` reports the
length that GET sends. (#44734)
- `bun:sqlite` and `node:sqlite`: if `iterate()` left a write unfinished
on a connection that has a hook, a user function or an authorizer, the
write is finished on the connection's next call instead of during
garbage collection. If the database is gone too, it's rolled back.
- `bun test --bail` runs exit listeners and closes SQLite databases.
(#39010)
- Dev server: a request for a client script waits while a bundle is in
flight (#42733), query strings reach framework routes (#33232), and a
request gets a 500 instead of hanging when plugins fail (#36812).

#### File formats

- `.jsc` bytecode files get a 24-byte footer so they can be verified
before decoding. Files from an older Bun are ignored and the source is
parsed instead. (#39396)
- `node:vm` `cachedData` gets an 8-byte checksum. A blob from an older
Bun is rejected, which the API allows. (#32839)
- The built-in modules section of a compiled executable changes from
format 1 to 2 and carries an engine stamp. (#44907)

#### Performance

Measured in instructions per operation on release builds of this branch
and its base, with an A/A run for the noise floor (0.0 to 0.2 %).

No change: `Bun.serve`, `node:http`, WebSocket echo and publish, `bun
build` of 3,807 modules, `bun run` with 2,000 imports, `readdir` /
`Glob` / `fs.cp` over 23,689 entries, startup and RSS. The binary grows
by 176 KB (0.17 %).

| Faster | Instructions |
| --- | --- |
| WebSocket echo of a 1 MB non-ASCII text message | −72 % |
| `Bun.inspect` of a large non-ASCII string | −39 % |
| `Bun.markdown.html` on large non-ASCII input | −33 % |
| `` $`cmd` `` with 300 environment variables | −6 % |
| `fs.readSync` | −5 % |
| `TextEncoder.encodeInto`, short ASCII strings | −4 % |
| async `crypto.pbkdf2`, 16-byte inputs | −17 % |

| Slower | Instructions | Why |
| --- | --- | --- |
| `cc()` calls | +5 to +51 per call | Argument count and type checks,
and a check for `close()` (#37989, #38057, #43802, #44921). `dlopen()`
calls don't change |
| `process.env.X = v` | 38 → 593 per write | Writes aren't cached. Reads
don't change (#38871) |
| async `crypto.pbkdf2`, inputs of 1 KB or more | +4 to +9 % | Password
and salt are copied (#40554) |
| `bun build` with an object `--define` used thousands of times | +4.5 %
| The object is copied per use (#45969) |

#### Not included

- Fixes that need a WebKit change: #39967, #42534, #42982, #43764,
#43786, #44226. #42185 too: a typed array that has no `ArrayBuffer` yet
can't be pinned, so `view.buffer.transfer()` during an async call can
still free its bytes. Creating the `ArrayBuffer` up front costs 7 to 12
% on every async `fs` call, so the fix belongs in JSC: an `ArrayBuffer`
created while the view is borrowed should start out pinned.
- #45442 (`calc()` sums as a flat list): it changes minified output for
real stylesheets to survive a `calc()` with 25,000 terms. It deserves
its own review.
- #40023 (Windows event loop redesign), #29928 (Windows exit path),
#40534, #43963, #39571, #42904, #42834, #36355, #43266: refactors or
features whose crash is already covered or isn't a crash.
- The pull requests marked *(crash fix only)* below should stay open for
their other half.

### How did you verify your code works?

- **Tests.** Every fix has a test that fails on `main` (a release or an
ASAN build) and passes on this branch, except where that isn't
practical: code that only runs on Windows or macOS, inputs that need
several GB of memory, and a few rare races. Those were checked by hand
or by reading.
- **Stored repro scripts.** 230 crash repros ran on release and ASAN
builds of this branch and of `main`, side by side. Release: 88 no longer
crash. ASAN: 106 no longer crash. None crashes that didn't before. What
still crashes needs WebKit, is SQLite's own bug, or isn't a crash. The
ASAN number is from a later commit than the release number.
- **Dev server.** Because one fix makes requests wait, 2,171 generated
programs ran random interleavings of edits, build errors, failing
plugins, reloads, stops and disconnects with about 120,000 requests. No
request hung, was answered twice or got a stale body. `main` hung in 82
of 1,161 programs. This also found the four dev server bugs listed
above.
- **Path helpers.** 336,000 boundary cases with buffers of exactly the
computed size, and 12,003 random calls through 30 JS APIs on an ASAN
build, compared with `main`. No sanitizer report, and the results match
wherever `main` doesn't panic.
- **What worked on 1.4.3 still works.** Reviewers compared behavior with
1.4.3 and took out what changed it: for example an output directory
layout change for 9 or more entry points, a `server.reload()` change,
and a changed error message for `import("file:///50%deposit.ts")`.
- **Not run locally:** the Windows, macOS and FreeBSD code paths. CI
compiles and tests them.

### Included pull requests

**Bundler, transpiler, CSS, macros** (33)

- #33881 bundler: allocate wrapper_ref for CommonJS modules with no
non-hoistable statements
- #35055 Bun.build plugins: handle filter RegExp flags beyond i/m/v
- #37769 bundler: fail the build instead of panicking when the bundle
thread cannot create its waker
- #37784 bundler: copy inlined env values into the define arena, and
give each Bun.build its own env copy *(crash fix only)*
- #37858 bundler: fail the build instead of panicking when a plugin
answer string cannot be converted
- #38046 bun build --server-components: require the bun target and
reject directives without a framework *(crash fix only)*
- #38095 js_parser: fix panic on decorated declare/abstract fields in
class expressions with experimentalDecorators
- #38966 bundler: keep deep CSS, export star and composes graphs from
overflowing the linker's stack
- #38984 bundler: stop an export star ambiguity that loops back into a
re-export chain from overflowing the stack
- #39113 css: reject stylesheets of 2 GiB or more instead of aborting on
an int cast
- #39396 bundler: frame .jsc bytecode sidecars and verify them before
decoding
- #39855 bundler: join the work still on the pools before the bundle is
torn down *(crash fix only)*
- #41157 dev server: leave out an html link to a cached json module
instead of panicking, and mark a new placeholder file stale
- #41801 css: decode ill-formed UTF-8 to U+FFFD before tokenizing
*(crash fix only)*
- #41827 bundler: handle YAML and JSON5 keys that are not strings
instead of panicking
- #42242 js_parser: compress symbol link chains when following merged
declarations
- #42387 bundler: check receivers on the Bun.build plugin object and
freeze its filters during a build
- #42413 Bounds-check the InternalSourceMap window reader
- #42657 macros: keep visited values alive so a reused address does not
get another value's Expr
- #43330 transpiler: do not print an empty `var` for a data file with no
named export
- #43355 bundler: fix "The memory limit has been exceeded." on large
HTML entries
- #43658 react-compiler: fix skipped functions and build aborts for dead
code in a try body *(crash fix only)*
- #44137 js_parser: fix four crashes of exports.eliminate and
exports.replace
- #44467 js_parser: replace skipped expressions with E::Missing and skip
argument checks after a stack overflow
- #44662 js_parser: walk binary chains on the heap and check the stack
when rewriting decorated #private accesses
- #44712 json5: reject sources of 2 GiB or more before parsing instead
of aborting on an int cast
- #44864 js_parser: walk conditional chains in import()/require() and
define keys in a loop
- #44883 js_parser: reject a decorator on a class static block, keep
decorators out of the body of `declare global` *(crash fix only)*
- #45045 Fix a segfault in new Bun.Transpiler(): re-point options.log
after the constructor moves its Log
- #45604 css: keep a url() in an at-rule prelude as written, and never
print the resolved path of a url() *(crash fix only)*
- #45748 bundler: put --banner/--footer in the bytecode ESM module
record (flags from a parse, entries from JSC) *(crash fix only)*
- #45960 macros: give each parse-worker macro VM its own env loader
- #45969 js_parser: copy object and array defines per use, and copy the
list of a lone JSX spread object *(crash fix only)*

**`bun build --compile` and standalone executables** (3)

- #31787 Don't crash at startup when a standalone executable's embedded
graph is corrupted *(crash fix only)*
- #38251 compile: exit with an error instead of SIGBUS when a standalone
executable is truncated
- #41360 standalone: check every offset in the embedded module graph
before reading it

**Resolver, module loading, plugins, paths** (25)

- #32269 Bun.plugin: validate the namespace without a shared regex
- #33183 bun:jsc: filter internal cells out of getProtectedObjects()
- #34575 Don't register native functions as their own constructors
- #36340 paths: size the thread-local join output buffers to
MAX_PATH_BYTES on Windows
- #37037 mock.module: reject async factory results that are not objects
- #37065 bun:jsc: propagate JSONParse exceptions from
samplingProfilerStackTraces
- #37529 resolver: don't abort on a package.json sideEffects entry
longer than the join buffer
- #38179 node:module: throw instead of crashing when module._compile is
set to a non-function
- #38273 bun test: report a test file or preload the loader cannot
resolve instead of exiting; keep the JUnit report valid U… *(crash fix
only)*
- #38732 paths: compute the common path of 9+ inputs with the same loop
as fewer *(crash fix only)*
- #39228 paths: strip C:\\ down to the drive root in
without_trailing_slash_windows_path *(crash fix only)*
- #39650 bun run --filter: stop panicking on workspace paths longer than
the path buffer
- #40186 resolver: stop deeply nested exports targets from overflowing
the stack
- #40258 resolver: publish Entry.abs_path through the per-entry mutex
- #42183 node:module: reject a _resolveFilename override result that
contains a null byte
- #42401 node:module: accept any `this` in Module.prototype.require
*(crash fix only)*
- #42405 Bun.plugin: transpile a copy of typed array onLoad contents
- #42414 node:module: end the Module._stat path at the first null byte
- #42685 resolver: strip the trailing separator inside bust_dir_cache
- #42735 Throw a RangeError instead of aborting when require.resolve
paths or Worker preload outgrows its Vector
- #43067 Report a path that does not fit a path buffer instead of
aborting *(crash fix only)*
- #44410 Fix a crash when code from a node:vm context reads
require.cache or require.extensions
- #44466 Trace the value an object or data module exports from its
JSSourceCode
- #45044 Bun.plugin: give onLoad's args.path its own bytes
- #45117 cjs: do not call an `__esModule` getter during the annotation
lookup

**Dev server, `bun bake`, routers, `--watch` and `--hot`** (28)

- #28793 Stop file watcher thread before Global.exit tears down memory
*(crash fix only)*
- #32143 bake: fix "Runtime file not found" panic in production builds
of custom frameworks
- #32443 watcher: don't free the Watcher in the spawn-to-start window
*(crash fix only)*
- #33232 bake: normalize the HTTP request-target before matching
framework routes
- #36812 bake: respond 500 and release both RequestContext refs when
on_plugins_rejected / OOM drains a deferred framework r…
- #37039 bake: report per-file print failures in the dev server instead
of serving empty modules
- #37276 hot_reloader: take entries_mutex for watcher-thread directory
cache probes
- #37444 bake: unregister Bake::SourceProvider from the source map table
when it is destroyed
- #39290 FileSystemRouter: match / against a root-level optional
catch-all route *(crash fix only)*
- #39291 FileSystemRouter: order dynamic routes by per-segment
precedence like Next.js *(crash fix only)*
- #39629 watch: report a failed watcher init as an error instead of a
crash
- #41185 bake: check for exceptions in the production build's module
loader hooks and helpers
- #41340 bake: skip the directory watch when the directory cannot be
opened
- #41617 Decide a directory watch event from the watchlist, not from the
resolver's cached listing *(crash fix only)*
- #42547 bake: re-arm the memory visualizer timer when it fires
- #42733 dev server: make a client script request wait for the bundle in
flight
- #42828 bake: serve routes from a router root outside the project root
instead of aborting or answering 404
- #42831 bake: resolve app.root and router roots through one checked
join
- #42836 bake: report route scan errors instead of aborting, and fail
bun build --app on them *(crash fix only)*
- #42840 dev server: map a router type's server entry point to the root
route of that type
- #42862 Bun.serve: return before a pending app.plugins setup() settles
*(crash fix only)*
- #42920 Do not create a mimalloc heap per FileSystemRouter, reload() or
:nth-child(An-B) selector
- #42934 dev server: register a client component without evaluating it
- #43329 dev server: check the route bundle index of a client script URL
before Index::init
- #44249 fs.watch: read each directory and close it before descending
- #44344 Windows: fix a watcher panic and lost events in a burst of file
changes, and a --hot that stops watching a deleted…
- #44744 dev server: answer a cached-file lookup only for a graph that
bundled the file
- #44746 dev server: keep an importer in its own graph when an import
fails or is deleted

**`Bun.serve`, sockets, HTTP, WebSocket, HTTP/2, QUIC, DNS** (28)

- #42667 Reland "usockets(windows): keep a closed poll alive until the
outer tick and libuv are done with it" (#39643)
- #33015 fix(windows): segfault in uv__wake_all_loops after system
resume *(crash fix only)*
- #35761 node:quic: detach lsquic ctx pointers before the finalize-order
sweep at worker VM teardown
- #37082 Bun.serve: terminate FIFO/pipe file responses at EOF
- #38024 dns: keep the c-ares uv_poll_t alive while its poll callback is
on the stack (Windows)
- #38636 serve: fix route use-after-free after reload() with
tls.serverName *(crash fix only)*
- #40888 server.fetch: copy a Headers argument instead of adopting the
wrapper's pointer
- #41337 Update lsquic to 4.9.4 and free unsent stateless resets on
destroy *(crash fix only)*
- #41384 usockets: hold a tick level for the whole of close_all
- #41412 Windows: wait for close completions when closing a worker's uv
loop
- #41516 node:http2: handle an empty byte range in respondWithFile and
respondWithFD
- #41521 udp: report every binaryType from the getter, reject a dgram
bind of the other family *(crash fix only)*
- #42188 net: do not assert a two-character host in SocketAddress.parse
- #42210 libuv(windows): keep a pipe's completed read counted until its
read callback returns
- #42334 fetch, Bun.serve: throw a RangeError for Headers that total 4
GiB or more *(crash fix only)*
- #43738 usockets: close a socket whose resume the kernel refuses from
the loop, not from the caller
- #44338 node:http: response trailers travel with the end call of the
response *(crash fix only)*
- #44433 bake: make the parked-request list non-owning and look up the
DevServer when a plugin load settles
- #44533 node:quic: capture the handshake while the conn is alive, set
the application at session creation
- #44734 Bun.serve: answer HEAD for an S3-backed Blob body without an S3
stat
- #44751 node:quic: close() waits only for opened streams, and lsquic
sends no GOAWAY before HTTP/3 starts *(crash fix only)*
- #44897 node:http2: throw instead of panic when the native
setNextStreamID() misses its argument
- #45076 node:http2: let close() and destroy() win over the refusal of a
request
- #45341 uws: AsyncSocket::write takes a size_t length, so res.end()
sends a body of 2 GiB or more whole
- #45522 node:http2: throw for an ALTSVC frame that is too long and for
a pushPromise id that is not a stream id
- #45676 node:quic: do not reset a stream lsquic has already finished
- #45822 node:quic: name a stream in queued session events by a
per-session key, not by its address
- #45858 Bun.serve WebSocket: a message that does not fit in memory
fails one connection, not the server *(crash fix only)*

**Streams, Blob, S3, files, `node:fs`** (28)

- #33845 io: propagate IoRequestLoop init failure instead of aborting
*(crash fix only)*
- #36365 prompt: drop debug_assert that rejects answers containing CR
- #37090 Deliver FIFO bodies whose writer connects after the reader
opens *(crash fix only)*
- #38039 node:fs: stop fs.copyFile(src, "") from segfaulting on Windows
- #38653 shell(cp): reject copying a directory into itself; walk cp
trees without recursion
- #39207 Convert scope-object receivers in the chaining functions and
inspect.custom fallbacks
- #39390 Blob deserialize: reject over-long paths, treat size >=
MAX_SIZE as unknown, make slice() non-panicking
- #39639 fetch: drop the upload and drain hop refs at VM teardown
*(crash fix only)*
- #40008 inspect hooks: copy user options with putDirectMayBeIndex
*(crash fix only)*
- #40462 Windows: FileSink.start({ path }) on a live writer: hand the
writer a libuv fd and close the old source *(crash fix only)*
- #41440 node:fs: pass the buffer to the read/readv/write/writev
callback on error
- #41584 Walk the timer pairing heap without recursion
- #41608 native-readable: accept a stream with no native handle
- #41710 JSSink write(): convert the chunk before resolving the native
sink *(crash fix only)*
- #42711 webstreams: bound the native recursion through a chain of tees
or text streams
- #43264 fetch: reject a file: URL whose path has an encoded NUL
- #43709 s3: fix double free of a multipart part's bytes on worker
terminate
- #43950 streams: link readers and writers last, reject their promises
as handled
- #44036 PipeReader: label a chunk Eof only when the reader is at its
end
- #44181 streams: throw instead of aborting when a direct stream's text
sink cannot take a string chunk
- #44195 fs: validate POSIX directory records in one parser, report a
malformed record as EIO *(crash fix only)*
- #44269 streams: join the string chunks of a text consumer with one
allocation
- #44490 watch(windows): report a failed child spawn as an error instead
of a panic *(crash fix only)*
- #44954 process.stdout/stderr with no FileSink: write synchronously,
reset after a failed write *(crash fix only)*
- #45004 streams: leave a stream alone when a consumer fails to lock it
- #45521 FileSink: throw ERR_ILLEGAL_CONSTRUCTOR from the constructor
that script reaches by writer.constructor
- #45738 s3: own the Blob store across the calls that run user JS
- #45975 node:stream: do not touch the web controller after the web side
is done

**Node-API, V8 API, `bun:ffi`, `process.dlopen`** (15)

- #36609 napi: implement uv_cwd on POSIX
- #37989 bun:ffi: stop cc() from turning non-numeric pointer arguments
into garbage pointers
- #38057 bun:ffi: make cc() reject non-numeric i64/u64 arguments instead
of passing garbage
- #38425 bun:ffi: throw on an empty cc() source array instead of
panicking
- #39652 napi: implement uv_async_t, uv_queue_work and uv_default_loop
on posix
- #39805 Share one handle scope implementation between Node-API and the
V8 API
- #39892 napi: implement uv_idle_t, uv_prepare_t, uv_check_t and
uv_timer_t on posix
- #40144 bun:ffi: return undefined for a NULL napi_value from cc() and
throw the scheduled napi exception
- #40773 bun:ffi: add the full byteOffset in read.*, do not truncate it
to int32
- #41704 napi: hand the thrown value to
napi_get_and_clear_last_exception after napi_run_script
- #42960 process.dlopen: run a V8 addon's init function after dlopen()
returns
- #43797 Fix debug assertion on an empty error message from a V8 addon
or SQLite *(crash fix only)*
- #43802 bun:ffi: throw a TypeError when a cc() symbol is called after
its library's close()
- #43940 napi: fail with ERR_BUFFER_TOO_LARGE instead of aborting above
the ArrayBuffer limit *(crash fix only)*
- #44921 bun:ffi: pad a short call to a cc() symbol with undefined

**`node:vm`, workers, process, timers** (19)

- #34623 node:vm: run DONT_CONTEXTIFY contexts directly against the real
global
- #32839 node:vm: reject invalid cachedData instead of crashing
- #36921 error printer: clear the pending exception when formatting a
non-Error uncaught value throws
- #37270 error printer: one render per error, [Circular] under the key
that closes the cycle
- #38740 bun:test: give each VM its own fake clock *(crash fix only)*
- #39864 Report a refused HTTP, bundle, IO or process waiter thread as
an error instead of a crash *(crash fix only)*
- #39992 process: deliver exceptions reported against a node:vm context
to uncaughtException
- #41654 node:vm: give each SourceTextModule request the import
attributes of the declaration that created it *(crash fix only)*
- #41739 Do not forward the inherited IPC channel to spawned scripts and
tools
- #41769 node:vm: stop compiling accepted cachedData, report each
cachedData decode to the GC *(crash fix only)*
- #42045 bun:test fake timers: never move the fake clock backwards
- #42308 process.execve: throw instead of aborting for a string past the
string limits
- #42734 node:vm: report cachedData of 2 GiB or more as rejected instead
of aborting
- #42843 process.dlopen: reject a filename of PATH_MAX or more before
dlopen()
- #43500 process: accept SIGSTKFLT, SIGPOLL and SIGPWR, and emit every
name of a signal number *(crash fix only)*
- #44486 worker: stop the start sequence when a handler it calls stops
the worker
- #44771 timers: allocate ids from one 64-bit counter that never wraps
- #44837 --hot: defer a reload during the preloads, and report a reload
that cannot start
- #44991 Fix a use-after-free in the VM ref-string intern for a string
over the length limit

**Shell, spawn, CLI, `bun test`, `bun install`** (31)

- #30642 Fail fast at startup when simdutf has no usable implementation
for this CPU
- #34223 Fix four crashes: HTMLRewriter disturbed body, S3 locked-stream
upload, ConnectionsList closed parser, shell brace… *(crash fix only)*
- #34884 Guard the console and test-runner formatters against native
stack overflow on deeply nested values *(crash fix only)*
- #36584 process.chdir: publish an immutable cwd slice so no thread sees
a torn cwd
- #37135 bun test --parallel: hold the JSC API lock while draining the
worker's final IPC backlog
- #37527 shell(mv): report ENAMETOOLONG instead of panicking when a
source name does not fit the path buffers
- #37528 cli: stop aborting on absolute script paths longer than 1024
bytes on Windows
- #38162 shell(cp): report ENAMETOOLONG instead of panicking on operands
longer than the path buffers
- #38205 shell(windows): report ENAMETOOLONG for operands that do not
fit the path buffer
- #39010 bun test: exit through the VM teardown path when --bail stops a
run
- #39104 bun test: report over-long coverage dir, JUnit outfile and
bunfig root instead of panicking *(crash fix only)*
- #39638 shell(cat): serve a second cat on the same stdin instead of
hanging or panicking
- #39641 usockets: report an out-of-descriptors event loop init as an
error, not a crash *(crash fix only)*
- #40181 shell: stop deeply nested if clauses from overflowing the
parser stack
- #40885 shell: throw instead of panicking when a ReadableStream is used
as a redirect
- #41155 ipc: send a queue item larger than 2 GiB in capped write
requests
- #42298 bun:test: print String objects with 16-bit storage correctly
- #42577 bun:test: root the return values toHaveReturnedWith collects
- #43606 shell(windows): report a failed pipe reader start through
on_reader_error instead of leaking the subprocess *(crash fix only)*
- #43838 node:cluster: read a worker's `ack` and `addressType` in the
primary only when they are int32
- #44172 node:cluster: refuse a descriptor of the wrong kind in the
primary *(crash fix only)*
- #44185 node:cluster: one handle for each descriptor that workers name
*(crash fix only)*
- #44491 bun test: run every callback when native code leaves an
exception pending *(crash fix only)*
- #44694 shell mv: refuse to copy a directory into itself on the
cross-device fallback
- #44752 shell: take the command-substitution capture and drop its NUL
bytes
- #44981 shell: reject NUL bytes in .cwd() and .env() at the native
setters
- #45206 ini: reject a source of 2 GiB or more in Parser::parse instead
of aborting on an int cast *(crash fix only)*
- #45348 bun test: fix a segfault in .not.toThrow(Class) when
Symbol.hasInstance accepts a thrown string, symbol or BigInt
- #45649 shell: replace the output counters in mkdir, cp, ls and touch
with the OutputTask queue
- #45792 bun test: SIGKILL a spawnSync child that is still running 500
ms after the test's timeout *(crash fix only)*
- #45910 create: own the remote-template response buffers instead of
parking them in the CLI arena

**Web APIs, Buffer, encoding, URL, crypto, zlib, SQLite, Redis and the
rest** (96)

- #29709 console: guard JSX/Proxy recursion in Bun.inspect (stack
overflow SIGSEGV)
- #30817 console.takeHeapSnapshot: clear prior snapshots before building
- #30956 spawnSync: make signal-forwarding register/unregister safe for
concurrent callers *(crash fix only)*
- #31505 node:zlib: reject invalid brotli flush values at validation
*(crash fix only)*
- #31735 node:path: fix win32 drive-relative resolve on non-Windows
hosts *(crash fix only)*
- #32085 Fix crash when RedisClient onclose/onconnect is set to a
non-callable
- #32240 Fix BroadcastChannel custom inspect crash with numeric option
keys
- #33181 Reject interior null bytes in Bun.mmap, Glob.scan, and
FileSystemRouter paths *(crash fix only)*
- #33752 node:crypto: validate EC JWK private scalar matches public
point in createPrivateKey
- #34976 spyOn: install and restore through one writer that throws when
the object refuses *(crash fix only)*
- #35562 structuredClone: purify NaN in deserialized Date timestamp so
getTime never returns a forged JSValue
- #35618 napi(windows): load addons that import node.exe without
win_delay_load_hook
- #35757 Coerce later arguments before capturing input buffers in
Bun.Transpiler and Bun.RedisClient
- #37252 Report UTF-16 to UTF-8 encode counts through size_t so exactly
2^32 written bytes doesn't wrap to 0
- #37338 node:module: build require.cache without user-writable globals
and propagate its exceptions *(crash fix only)*
- #37340 redis: accept unsubscribe acks that arrive outside subscriber
mode
- #37370 Error.appendStackTrace: make appending an error's trace to
itself a no-op
- #37443 node:crypto: fix null deref when worker.terminate() lands
during an EC JWK private key import
- #37448 jsc: check for exceptions before using a stored
constructEmptyArray result *(crash fix only)*
- #38009 MessagePort: fix a heap-use-after-free in contextDestroyed(),
release ref() when the last 'message' listener is rem… *(crash fix
only)*
- #38469 napi: settle or refuse async work queued during VM teardown
instead of taking a ticket
- #38708 Handle 16-bit module sources in the error preview, the
new-position fix-up and the REPL *(crash fix only)*
- #38821 process.env: make a failed env build throw instead of aborting
(Windows 0xC0000409 on Bun.$ / Bun.sql / process.env…
- #38871 process.env: coerce to string on every execution of an
assignment, not just the first
- #38877 cli: exit 128 + signo when bun cannot die from a re-raised
signal (bun as container PID 1)
- #38926 Clear the inherited signal mask at startup and exec children
with an empty one *(crash fix only)*
- #39382 Make a failed util.inspect load throw from custom inspect
functions instead of aborting
- #39481 Always create the error when a native error message exceeds the
string length limit
- #39651 performance: keep the user timing entry counts exact after
clearMarks(name) and clearMeasures(name)
- #39775 Turn seccomp SIGSYS traps into ENOSYS so the syscall fallbacks
run on Android
- #39968 process.dlopen: replay a non-context-aware V8 addon only while
no other live VM owns it
- #39975 watch: report a failed reload exec as an error instead of a
panic *(crash fix only)*
- #40346 Give Glob's native scan methods their own private names
- #40554 node:crypto: copy password and salt for async pbkdf2 and scrypt
- #40567 url: reject URL-encoded input over the WTF decode limit instead
of aborting
- #40577 url: throw a RangeError instead of aborting when
URLSearchParams or FormData outgrows its Vector
- #41073 Store array-index property names as indexed properties in
native object builders
- #41137 Write the sampling profiler report at exit from Bun, not JSC's
atexit hook
- #41365 webview: fail only the view when WebKit lacks
initWithDirectory:
- #41574 Decode a private copy of a JS buffer in the UTF-8 decoders
*(crash fix only)*
- #41652 console: read a BigInt depth option by value in console.dir
- #41749 Startup: reopen fd 0-2 as /dev/null only when the fd is closed
- #41819 Report an incoherent BUN_JSC_* option combination as a
configuration error, not a crash *(crash fix only)*
- #42158 webview: reject malformed Chrome replies instead of crashing
- #42179 shell: clamp a `> ${buf}` redirect to the target buffer's live
length
- #42187 node:crypto: throw ERR_OUT_OF_RANGE for >2 GiB buffer arguments
instead of aborting
- #42191 URLPattern: throw instead of aborting when a pattern string
passes the string limit
- #42192 Copy WebAssembly.Memory bytes for native borrows that outlive
the call *(crash fix only)*
- #42198 Make Bun.$, Bun.sql, Bun.postgres and Bun.SQL custom value
getters so reifying the Bun object passes exception chec…
- #42203 node:fs: fs.read into a WebAssembly.Memory view writes into the
block a grow freed
- #42214 Headers: throw a RangeError instead of aborting when the
set-cookie list cannot grow
- #42218 Headers: throw instead of aborting when a value passes the
string length limit
- #42220 URLPattern: throw instead of aborting when the token list
cannot grow
- #42225 Throw ERR_STRING_TOO_LONG from Bun.wrapAnsi instead of aborting
when the output passes the string length limit
- #42226 Throw instead of aborting when a MIME string does not fit in a
string *(crash fix only)*
- #42237 Bun.Cookie: throw instead of aborting when the Set-Cookie
string passes the string length limit
- #42249 Copy a shared input before libdeflate compresses it in
Bun.gzipSync and Bun.deflateSync
- #42253 bun test: walk nested describe scopes without native recursion
- #42259 Throw instead of aborting when a domainToASCII host passes the
string length limit
- #42310 Parse a private copy of a shared or resizable buffer in
Bun.Transpiler, Bun.markdown, Bun.YAML and Bun.TOML *(crash fix only)*
- #42312 YAML, JSON5, XML stringify: throw instead of aborting when the
output passes the string length limit
- #42318 Bound libdeflate's emit path so a racing input cannot overrun
the output
- #42338 inspector: check the type of process.argv in getModuleGraph
- #42364 node:perf_hooks: do not truncate the monitorEventLoopDelay
resolution to int32
- #42412 transpiler cache: reject an entry with no sourcemap section
- #42479 worker_threads: do not abort when
markAsUntransferable/markAsUncloneable gets a WebAssembly GC reference
- #42517 EventTarget: skip a listener object that has no realm
- #42518 fs.Stats: make the date accessors define the property like
Object.defineProperty *(crash fix only)*
- #42575 Stop natives from writing onto a foreign `this` with putDirect:
process.ppid, require.cache, StringDecoder, the nat… *(crash fix only)*
- #42631 JSStringView: pin the cell that owns the borrowed characters
- #42660 bun_core: read /dev/urandom when getrandom(2) answers ENOSYS or
EPERM
- #42780 node:crypto: treat a name too long to convert to UTF-8 as
unknown instead of aborting
- #42782 node:crypto: throw ERR_OUT_OF_RANGE for a passphrase larger
than INT_MAX bytes
- #42856 url: do not abort when a host is too long for the IDNA
conversion buffers
- #42868 sqlite, console, process: do not abort on a string too long to
convert to UTF-8 *(crash fix only)*
- #42941 Bun.sliceAnsi: throw instead of aborting when the result passes
the string length limit
- #43058 Bun.serve: fix crash and cross-request 500 when inspecting a
non-Response return value throws
- #43904 JSC bindings: build property keys from a BunString through
Bun::toIdentifier
- #44124 Bun.Image: decode WebP into a Bun-owned canvas and read ICCP
without the demuxer *(crash fix only)*
- #44190 Convert scope-object receivers before Buffer read*/write* and
vm.Script describe them
- #44211 Stop getsockname(out), useFakeTimers() and the stream source
pull() from writing onto a caller's object with putDirect
- #44295 bun test --coverage: append a final newline to a text that
lacks one *(crash fix only)*
- #44360 rust-argon2: return OutOfMemory instead of aborting when the
memory cost cannot be allocated
- #44421 node:zlib: free zstd's workers before the dictionary they read
- #44521 util.parseArgs: pick the default args start from a per-VM eval
flag, as Node v26 does *(crash fix only)*
- #44740 structured clone: tolerate a zero-sized shared
WebAssembly.Memory in computeMemoryCost()
- #44759 HTMLRewriter: park a suspended handler's token before the
output flush
- #44907 Builtins section format 2: an engine stamp says which buns
compile its modules
- #45188 Reject an oversized WebCrypto cipher output instead of aborting
- #45354 Throw for a `file:` URL whose path is not UTF-8 on Linux and
macOS, through one `fileSystemPath()` accessor *(crash fix only)*
- #45608 ipc: refuse an over-long message before the receive buffer
stores it
- #45624 webcrypto: write the key type into the X25519 structured-clone
record
- #45625 node:sqlite: refuse session.close() and Symbol.dispose inside a
SQLite callback
- #45653 glob: a group with `?` or a class matches when an alternative
takes 64 bytes or more
- #45820 Bun.file, S3Client.file and Bun.write no longer keep a buffer
path alive forever
- #45832 `bun check`: fix a panic on `export *` without a module
specifier, and a false error for one in parentheses

### Already fixed on `main`, or duplicates of a pull request above

Already fixed: #27323 #30401 #31011 #31206 #31566 #31626 #31695 #31702
#31945 #32773 #34154 #34697 #34744 #34964 #35655 #35816 #36020 #36181
#36296 #36342 #36581 #36602 #36807 #36818 #36857 #37172 #37235 #37239
#37267 #37420 #37731 #37914 #38113 #38119 #38509 #38514 #38540 #38975
#39410 #40749 #41163 #41171 #42108 #43085 #43230

Duplicates: #45654 #29986 #33378 #36895 #37070 #37639 #38014 #39021
#41266 #42250 #42951 #43238 #44259 #45335 #45565 #45726 #45965

Fixes #5019
Fixes #6106
Fixes #10690
Fixes #10886
Fixes #13566
Fixes #14745
Fixes #15551
Fixes #20454
Fixes #21310
Fixes #29145
Fixes #30454
Fixes #30613
Fixes #30766
Fixes #32103
Fixes #32142
Fixes #32183
Fixes #32212
Fixes #39060
Fixes #42296
Fixes #42931
Fixes #43671
Fixes #44201
Fixes #44735
Fixes #44783
Fixes #45198
Fixes #45327
Fixes #45491
Fixes #45721

---------

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
@robobun

robobun commented Oct 21, 2026

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Closing: #45677 supersedes this PR. It rewrote the coverage report and removed the line lookup that aborted (LineOffsetTable::find_index).

On main at 9634520 the repro from this PR exits 0 and reports the last line of prebuilt.js. I also ran the 152 cases of this PR on that build: none aborts, and each file with no final newline reports the same lcov record as the same text plus a newline.

Reopen this PR if a file with no final newline still reports wrong.

@robobun robobun closed this Oct 21, 2026
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