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fix: don't drop stdin bytes when client-loss sender is gone - #1941
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The stdin arm of bridge_one raced cs.write_all against client_lost.wait_for in a single tokio::select!. write_all is not cancel-safe: when the client-loss sender is dropped, wait_for resolves Err immediately, and if select! polled that branch first the write future was dropped mid-flight, losing the bytes it had already accepted. Pin the write future and loop the select until it completes. A dropped sender now only disables the client-loss branch; the write always runs to completion, so every stdin byte reaches the child. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Navigate logical layers of code changes, visualize relationships, and explore their blast radius. 📝 WalkthroughWalkthroughThe child-stdin write loop now pins each write and polls it until completion. A signaled disconnect still marks the SSH write path as failed, while a dropped watch sender disables that branch. Write errors still close the child’s stdin. ChangesChild stdin write handling
Priority: ⬇️ Low Estimated code review effort: 2 (Simple) | ~10 minutes Change: Bug fix Suggested reviewers: Merge Risk: 🟡 Moderate · up to Exec commands that write output while receiving input can hang. Keep output draining while a stdin write is pending before merging. 🚥 Pre-merge checks | ✅ 5✅ Passed checks (5 passed)
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Actionable comments posted: 1
- 🪄 Fix CodeRabbit comments on this PR
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Inline comments:
Review comments at @crates/minimald/src/exec.rs:
- Around line 1179-1184: In the exec loop, keep pending child-stdin bytes and
their write offset in the outer select loop instead of awaiting write_all in the
stdin-read branch. This lets stdout and stderr reads continue while the
child-stdin write is pending; preserve partial-write progress and ensure a
genuine client-loss signal still reaches the child-kill path.
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crates/minimald/src/exec.rs
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Approved at 33b9b5d. This is the fix specified in gominimal/inbox#860. The pinned write_all with a looping select means a dropped client-loss sender only disables that branch and never cancels a write, and a real disconnect still breaks out and kills the child. CI is green apart from macOS e2e, which is waiting on the runner backlog. CodeRabbit's head-of-line blocking finding predates this PR and is tracked in gominimal/inbox#866.
✅ Action performedComments resolved and changes approved. |
Summary
Fixes a data-loss race in
minimald's exec bridge (crates/minimald/src/exec.rs).The stdin arm of
bridge_oneracedcs.write_allagainstclient_lost.wait_forin a singletokio::select!.write_allis not cancel-safe: when the client-loss sender is dropped,wait_forresolvesErrimmediately, and ifselect!polled that branch first the write future was dropped mid-flight — losing the stdin bytes it had already accepted.Fix
Pin the
write_allfuture and loop theselect!until the write completes. A dropped sender now only disables the client-loss branch (client_watch_open = false); the write always runs to completion, so every stdin byte reaches the child. A genuine client-loss signal still breaks out and kills the child as before.Verification
cargo fmt --all --check— cleancargo clippy --workspace --locked— clean (only pre-existing warnings)cargo build --workspace --locked— cleancargo test --workspace --locked -p minimald --lib— allminimaldtests pass, including the 10exec::tests::bridge_*testsexec::tests::bridge_round_trips_stdio_and_propagates_exit_code(the regression test, which uses a dropped-senderclient_lost()) passes repeatedlyNote: the full
--workspacetest run shows 2 pre-existing failures incrates/checkouts(checkout_of_branch_from_a_stale_manager_does_not_collide,offline_checkout_of_branch_from_a_legacy_cache_uses_the_local_ref), unrelated to this change.Routing-Key: inbox-route/I_kwDOSUhdos8AAAABU4bT2A
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