[SashaMIT]

Goal

trackPanic searched each stderr read on its own. A header that started in one read and finished in the next was forwarded as ordinary output, and the handler never ran. The skipped TestPanicWrap_panicBoundary is that case: the child writes pan, then ic: oh crap.

Changeset

Changed

trackPanic keeps a tail shorter than fatal error: and joins it to the next read before treating the text as ordinary output. On end of input that tail is written out. A read error ends the scan.

Tests

TestTrackPanic_splitHeader writes before pan and then ic: split through a pipe. On the old reader the panic text was empty and the boundary helper exited 2. After the join the handler sees panic: split, the prefix before is forwarded, and the boundary helper prints wrapped: 14.

go test -count=1 . passed.

Discussion

The held tail is one byte shorter than the longest header, so a split panic: or fatal error: is still visible. Ordinary output waits for the next read, or for the stream to end.

Review

• Reviewed the test cases added for completeness and possible points for discussion
• A changelog entry was added for the goal of this pull request
• Check the scope of the changeset - is everything in the diff required for the pull request?
• This pull request is ready for:
  • Final review