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When bun runs as `node`, process.argv[1] kept an absolute script argument as typed. So a launcher that runs `node "$basedir/../pkg/cli.mjs"`, or a Windows path with `/` separators, made `process.argv[1] === fileURLToPath(import.meta.url)` false. Node reports path.resolve(script). Add `resolve_path::resolve_spill`, the join to the cwd without the trailing separator, and use it for every script argument of the shim. The module loader resolves the entry from the same path, so `node ./pkg/` now runs the file that `node ./pkg` runs, as in Node.
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Status: ready for a maintainer. CI is green on build 118389, 181 of 181 jobs. The code head is 09ba153. The commit on top of it is empty and only started that build. How I reproduced it Linux x64, released build 1.4.3-canary.1+367d939d9, Node v26.3.0 for comparison. An absolute script argument stays as typed: echo 'console.log(process.argv[1])' > plain.js
node "$PWD//plain.js" # /tmp/nodedot/plain.js
bun --bun node "$PWD//plain.js" # /tmp/nodedot//plain.jsThe launcher that pnpm writes ( Windows x64, canary 1.4.3-canary.1+367d939d9:
Not fixed here: One decision for a maintainer: on Windows, |
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Inline comments:
In `@src/runtime/cli/run_command.rs`:
- Line 2977: Update the resolve_spill call in the script-resolution path to use
paths::platform::Auto instead of paths::platform::Loose, preserving literal
backslashes in POSIX filenames before passing the resolved path to Self::boot.
Add a POSIX test covering a script whose filename contains a literal backslash.
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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/runtime/cli/run_command.rs— Users who runnode ./pkg/with apkg.tsorpkg.mjsfile beside apkg/index.jsdirectory now get the sibling file run instead ofpkg/index.js, which both Node and the base branch run. The trimmed path from resolve_spill at run_command.rs:2977 is passed as the entry to boot at run_command.rs:2990, so the trailing separator no longer steers entry resolution to the directory and Bun's extension probe picks the sibling first. Fix: keepnode ./pkg/resolving to the same file as the base whenever Node would runpkg/index.js, for example resolve the entry from the untrimmed argument and only report the trimmed path inprocess.argv[1], or limit the sibling-extension probe to Node's extensions in the node shim. … [also at: src/runtime/cli/run_command.rs:2982 - Users who runnode ./pkg/through bun's node shim with apkg.ts,pkg.mjsor similar sibling now get that sibling instead ofpkg/index.js, which Node and the base branch run.]Extended reasoning...
…The PR notes call this a known trade-off deferred to #43409; the test at as-node.test.ts:143 certifies the divergence.
The base branch joined a relative argument with join_abs_string_buf::, which preserves a trailing separator, so
node ./pkg/booted with entry/cwd/pkg/and the loader picked the directory index. With this change resolve_spill strips the separator (src/paths/resolve_path.rs:1434-1437), so boot receives/cwd/pkg. Bun's entry resolution triespkg.tsx,pkg.ts,pkg.mjsand other extensions before the directory (see the 'entrypoint file extension picking' tests in as-node.test.ts:34-83), so a siblingpkg.tsorpkg.mjswins. Node's Module._findPath, given path.resolve('./pkg/') = '/cwd/pkg', tries only.js,.json,.nodeand then the directory, so it runspkg/index.jsfor a.tsor.mjssibling. A project withscripts.tsbesidescripts/index.jsinvoked asnode ./scripts/from…Verification: nit — acknowledged in diff: PR description ("Beside
pkg.tsorpkg.mjsit is the sibling, where Node and the released build runpkg/index.js") and the pinned test at test/cli/run/as-node.test.ts:133-142 (test.each(["pkg.js", "pkg.ts"])expects./pkg/-> "sibling"); the stated bound is accurate. Trigger: a project haspkg.ts/pkg.mjs(any extension Bun probes before a… | nit —…
The module loader resolves the entry from the same path that becomes process.argv[1], and a trailing separator selects the directory there. Bun tries `pkg.ts` before the directory `pkg`, so without the separator `node ./pkg/` ran a sibling `pkg.ts`, where Node runs `pkg/index.js`. Keep one trailing separator when the script argument has one. The rest of the path is still normalized. process.argv[1] of a directory argument then differs from Node by that separator, as it did before.
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robobun
changed the title
node shim like path.resolve()node shim
Move the script path step of exec_as_if_node into node_script_entry_path, so the name states why a trailing separator stays. Shorten two comments in resolve_spill. The device path comment now shows the wrong answer of the Windows join by example.
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On the finding about The first revision documented the change of file and recorded it in a test. That was the wrong call. A trailing separator in Of the two fixes you suggested, the first one (resolve from the typed argument, report the trimmed path) needs What this costs, measured:
The two tests "a trailing separator selects the directory" guard the file choice. On Linux they pass on the released build too, so they do not prove the fix there. On Windows they fail on the canary. The PR body is rewritten to match. |
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Updated 11:54 AM PT - Sep 19th, 2026
✅ @robobun, your commit 5e540f01652aa78b8dfd98d7ac8eac5c6eb32fdf passed in 🧪 To try this PR locally: bunx bun-pr 43454That installs a local version of the PR into your bun-43454 --bun |
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Problem
node,process.argv[1]keeps an absolute script argument as typed. Node reportspath.resolve(script). The pnpm launcher runsnode "$basedir/../pkg/cli.mjs", so underbun --bun runthe checkprocess.argv[1] === fileURLToPath(import.meta.url)is false, and a CLI behind it exits 0 and does nothing.node C:/proj/main.mjs, the form Git Bash passes.exec_as_if_node(src/runtime/cli/run_command.rs:2975). It does not normalize an absolute argument. No issue reports this.Fix
exec_as_if_nodepasses every script argument to the newresolve_path::resolve_spill, a join to the cwd that follows Node'spath.resolve. This fixes both cases.node ./pkg/still reports/abs/pkg/where Node reports/abs/pkg. Without it,node ./pkg/runs a siblingpkg.ts, where Node runspkg/index.js.node ./pkg/now runspkg/index.js. The canary dropped a trailing/there (but kept\) and ran a siblingpkg.jsorpkg.ts. On POSIX the file that runs does not change.test/cli/run/as-node.test.ts(released build: 4 of 8 new tests fail on Linux, 8 of 8 on Windows x64), and unit tables insrc/paths/resolve_path.rs. Self-reviewed: 8 concerns raised, 7 addressed. Rejected: a stack on Make the entry point of thenodeshim the main module #43409 (no conflict with it).Background
bun runandbun --bunput anodelink to bun first inPATH. With thatargv[0], bun runsexec_as_if_nodeon the first positional.vm.main.process.argv[1]reads it and the module loader resolves the entry from it, so one string serves both.Looseis the path platform that accepts/and\. On Windows it is the Windows join.Notes
Why the trailing separator stays. An earlier revision of this PR removed it, as
path.resolvedoes. Review showed that this changed which file runs. Bun tries a file with an added extension (.tsx,.ts,.mjs, and more) before a directory, and Node tries only.js,.jsonand.node. Sonode ./build/beside abuild.mjsranbuild.mjs, where Node and the released build runbuild/index.js. To report the trimmed path and still resolve from the typed one,process.argv[1]andvm.mainmust be two strings. #43409 and #35469 each add that (main_for_argv). The trim belongs on top of one of them. This PR does not add a third copy.Which file runs (a directory
pkg/withindex.jsand one sibling file):pkg.js./pkgpkg.jspkg.jspkg.jspkg.jspkg.jspkg.js./pkg/pkg.jspkg/index.jspkg/index.jspkg.jspkg/index.jspkg.ts./pkgpkg/index.jspkg.tspkg.tspkg.tspkg.tspkg.ts./pkg/pkg/index.jspkg/index.jspkg/index.jspkg.tspkg/index.jsOn Linux no row changes, and neither do 15 more rows with an absolute argument (
/abs/pkg,/abs/pkg/,/abs/pkg///,/abs/./pkg/,/abs/sub/../pkg/, each besidepkg.js,pkg.tsandpkg.mjs). On Windows the two./pkg/rows change. Thepkg.tsrow moves to Node's choice and thepkg.jsrow moves away from it. The Windows canary is not consistent with itself here: for the same directory it keeps a trailing\(.\pkg\, and every absolute form) and drops a trailing/on a relative argument. With this PR every form with a trailing separator selects the directory, on both platforms. The Linux rows were measured by hand. The Windows rows are the two tests "a trailing separator selects the directory", which fail on the canary and pass on this branch.The launcher, measured on Linux x64. The fixture has
node_modules/pkg/cli.mjswith the main check, theshlauncher that cmd-shim writes (pnpm uses it on every platform, npm on Windows) innode_modules/.bin/pkg, and"scripts": {"go": "pkg"}.bun runalso installs the shim without--bunwhen nonodeis inPATH, for example in theoven/bunimage.Comparison with Node v26.3.0 on Linux x64 (cwd is
/tmp/nodedot, 18 forms). The released build (1.4.3-canary.1+367d939d9) differs from Node on the 10 forms marked*. This PR differs on the 5 marked+, each only by the trailing/.Comparison with Node v26.3.0 on Windows x64. This ran on a Windows Server 2019 machine with a native debug build of this branch, 25 argument forms, exact string match. 22 of them run in Node. The canary differs from Node on 13 of the 22. This PR differs on 7: the 6 forms with a trailing separator (only by that
\), and 1 by the case of the drive letter. Examples:C:/workspace/scratch/argv2/plain.jsC:\workspace\scratch\argv2\plain.jsC:\workspace\scratch\argv2\.\sub\..\plain.jsC:\workspace\scratch\argv2\plain.js/workspace/scratch/argv2/plain.jsC:\workspace\scratch\argv2\plain.js//localhost/C$/workspace/scratch/argv2/plain.js\\localhost\C$\workspace\scratch\argv2\plain.jsC:/workspace/scratch/argv2/proj/C:\workspace\scratch\argv2\projC:\workspace\scratch\argv2\proj\Drive letter case. For
c:/x/main.mjsNode reportsc:\x\main.mjsforprocess.argv[1]and forfileURLToPath(import.meta.url). Bun's Windows join writes an uppercase drive letter, so this PR reportsC:\x\main.mjs. Bun'simport.meta.urlhas the uppercase letter too, so the main check is true. To keep the typedc:would makeprocess.argv[1](c:\...) differ from bun's own module path (C:\...), and the main check would be false again for every caller with a lowercase drive. Node's exact string needs bun's module URLs to keep the drive case, which is outside this PR.A
\\.\device path. The Windows join finds no volume in it and would answerC:\C:\foo\main.jsfor\\.\C:\foo\main.js.resolve_spillreturns such a path as given, which is what the released build does. Node, the canary and this PR all fail to run a\\.\C:\...or\\?\C:\...script.resolve_spillis the fullpath.resolve. It removes the trailing separator. Its unit tables run the POSIX and the Windows join on every platform, and each row is the output ofpath.posix.resolveorpath.win32.resolve. The two rows that differ from Node (drive case, device path) are in their own test. Only the call site inexec_as_if_nodeputs the separator back. #35469'sabsolutize_for_argvdoes the same join and strip, and can callresolve_spill.Not changed. A drive-relative argument (
C:plain.js) resolves against the cwd here and against the per-drive cwd (=C:) in Node.c:plain.jswith a cwd onC:is not found, before and after.require.main === module,Bun.mainandimport.meta.maindo not change.Looseis kept. On POSIX it also accepts\as a separator, sonode scripts\build.jsfrom apackage.jsonscript continues to work.platform::Autowould not keep a literal\either:normalize_string_buf_tsendsPosixandLooseto the same normalizer. Bun does not load a path with a literal\on POSIX, before or after this PR. Measured for an absolute argument with the\in the file name (/tmp/bsdir/a\b.js) and in a directory (/tmp/bsdir/we\ird/b.js), asnodeand as plainbun: Node runs both, bun runs neither, because it changes\to/below the CLI. What this PR changes there is the error text. For the file name form the message now names the normalized path and not the typed one. For the directory formENOENT readingbecomesModule not found, with the same path. A relative argument already went throughLooseon main.Why the spill variant of the join. An absolute argument did not go through a join before.
join_abs_string_bufinto a path buffer aborts on an argument longer than the buffer (the released build does that for a long relative argument).join_abs_string_spillhas no length limit, and--cwduses it too. #43067 edits the same call. The one that merges second gets a small conflict here.Related open pull requests. #35469 and #43347 change
process.argv[1]for a symlinked entry on the plainbun <file>path. Both leave thenodeshim as it is. #43409 makes the entry of the shim the main module and keeps the value ofprocess.argv[1].Other edge cases checked by hand on the Linux debug build.
node /andnode //printModule not found '/'. A long argument with a trailing separator does not abort. An absolute argument works from a deleted cwd./abs/link/../file.js, wherelinkis a symlink to a directory elsewhere, runs/abs/file.jsas Node does.Verification.
On Linux, 4 of the 8 new tests pass on the released build too: the two
/separator tests (a Windows-only failure) and the two "a trailing separator selects the directory" tests, which guard the file choice and do not prove the fix. Also green on the Linux debug build:bun-run.test.ts,bun-run-bunfig.test.ts,run-eval.test.ts.process-args.test.jshas one test,args exclude run, that exceeds its 5 s timeout on the ASAN debug build in this container. It starts 100 processes and does not use thenodeshim. Thebun_pathsunit tests do not link on Windows (MSVC keeps unresolvedbun_coreexternals), with or without this change. The 8 new tests run one after another, because they use this file's synchronousfakeNodeRunhelper.test/CLAUDE.mdprefers concurrent tests. This keeps the file's style and avoids a second spawn helper beside the async one that #43409 adds. The tests can move to that helper when it lands.[human-review] gate passed · iteration 1 · 3 files touched
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