🐛 Handle EPIPE on stdin in POSIX process implementation

[taras]

Summary

• Add childProcess.stdin error handler in POSIX createPosixProcess to suppress EPIPE errors when writing to stdin after child exit
• Non-EPIPE stdin errors are routed through processResult.resolve(Err(err)) — the same error propagation path used by trapError
• Add regression test that explicitly writes to stdin after child exit to verify no uncaught exception
• Bump @effectionx/process to 0.7.4

Root cause

The Windows implementation (win32.ts:130-137) already suppressed EPIPE on childProcess.stdin, but the POSIX implementation had no error handler at all. Any EPIPE from a write-after-exit became an uncaught exception.

Behavioral contract after fix

• EPIPE on stdin (write-after-exit during teardown or normal lifecycle race): silently ignored
• Non-EPIPE stdin errors: surfaced as operation errors via join()/expect()
• stdin.send() remains fire-and-forget (void return)

Test plan

• New test: stdin EPIPE handling > does not crash when writing to stdin after child exits
• New fixture: read-one-line.js — reads one line from stdin, confirms via stdout, exits
• Test explicitly exercises post-exit stdin.send() call
• All existing tests continue to pass (3 pre-existing failures on main are unrelated — stderr matching with Node's ExperimentalWarning)

Summary by CodeRabbit

• Chores

  • Bumped package version to 0.7.4.

• Bug Fixes

  • Improved handling of stdin errors when writing to already-exited child processes to prevent unexpected crashes and improve stability.

• Tests

  • Added tests covering stdin-after-exit scenarios to ensure robustness of the fix.

[coderabbitai]

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📝 Walkthrough

Walkthrough

Updated package version and added deterministic stdin "error" handlers on POSIX and Windows paths that suppress EPIPE (logging a warning) and surface other stdin errors by resolving the process result. Added a test and fixture that verify writing to stdin after child exit is handled without crashing.

Changes

Cohort / File(s)	Summary
Version Bump process/package.json	Bumped package version from 0.7.3 to 0.7.4.
Stdin Error Handling (POSIX) process/src/exec/posix.ts	Added a named stdinErrorHandler that suppresses EPIPE (logs a warning) and resolves non-EPIPE errors with Err(err); handler is removed in finally via .off().
Stdin Error Handling (Windows) process/src/exec/win32.ts	Refactored inline stdin error callback into stdinErrorHandler; suppresses EPIPE (logs a warning) and resolves non-EPIPE errors with Err(err); handler is removed in finally via .off().
Tests & Fixtures process/test/exec.test.ts, process/test/fixtures/read-one-line.js	Added stdin EPIPE handling test that writes to stdin after child exit and confirms no uncaught failure; added read-one-line.js fixture that reads one line then exits with code 0.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Suggested reviewers

• cowboyd

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Important

Pre-merge checks failed

Please resolve all errors before merging. Addressing warnings is optional.

❌ Failed checks (1 error, 1 warning)

Check name	Status	Explanation	Resolution
Policy Compliance	❌ Error	The process/package.json keywords array contains non-approved keywords (effection, effectionx, spawn, exec, child-process) violating the strict Package.json Metadata Policy.	Remove non-approved keywords from process/package.json and use only approved categories: testing, io, process, streams, concurrency, reactivity, interop, platform.
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the main change: handling EPIPE errors on stdin in the POSIX process implementation.
Description check	✅ Passed	The pull request description comprehensively covers motivation, approach, root cause analysis, behavioral contract, and test plan aligned with the template sections.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/process-posix-epipe

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[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@effectionx/process@198

commit: 4c05cca

[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@process/src/exec/stdin.ts`:
- Line 5: Duplicate tuple alias ProcessResultValue is defined in multiple exec
modules; extract it into a single shared module (e.g., create an api module) and
export it for reuse. Create/process/src/exec/api.ts with an exported type
ProcessResultValue = [number?, string?]; then remove the local alias from
stdin.ts, posix.ts, and win32.ts and replace with an import of
ProcessResultValue from that shared api module (or re-export from an index if
preferred) so all exec implementations reference the same type definition.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

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Run ID: 0cafae46-d53b-409c-b673-a29e8fb4b93d

📥 Commits

Reviewing files that changed from the base of the PR and between 4468d7d and fbbcee5.

📒 Files selected for processing (3)

• process/src/exec/posix.ts
• process/src/exec/stdin.ts
• process/src/exec/win32.ts

[joshamaju]

What if we also show a warning in dev mode?

[jbolda]

Mentioned in discord but for posterity:

Is there a case where we wouldn't want to no-op outside of shutdown? I suspect it is pretty safe to ignore in shutdown. I can't think of a truly useful situation, but gut says that it might be worth somehow allowing the user to deal with the errors outside of shutdown. A possible example may be that a process that starts, looks for user input, then runs "read only" to completion?

[cowboyd]

Why are we trying to write to stdin after it has been closed? In other words, shouldn't we be detecting stdin close when it happens?