[rush-daemon] Fix summary writer racing early coalesced results (main is red)

[Sean Larkin (TheLarkInn)]

Summary

main fails 3 @rushstack/rush-daemon tests with StdioSummarizer: The summary cannot be prepared until after close() is called. Two PRs that merged close together conflict at runtime, though not textually. This PR fixes that interaction, and both features keep working.

Fixed tests:

• PhasedRequestBatching: "publishes an early failure result while the batch continues for other clients"
• PhasedRequestBatching: "derives shared and disjoint failure results from each client subset"
• DaemonRequestWirePhased: "merges two connections into one shared iteration with subset-specific results"

Root cause (#6068 × #6092)

• [rush-daemon] Print the native operation summary and duration line on the daemon path #6068 added writePhasedRequestSummary. For a failed operation, it prints the native summary, which reads the failure tail from record.stdioSummarizer.getReport(). That call throws if the summarizer is still open.
• [rush-daemon] Publish coalesced phased results as soon as each client's own selection completes #6092 added the early per-client result path. PhasedRequestEventSink.onOperationCompleted calls #finishSettledEntry, which calls #produceResultAsync. That function writes the summary synchronously before its first await.
• onOperationCompleted is triggered from OperationExecutionRecord.finalizeOperation(). At every call site, rush-lib closes stdioSummarizer and problemCollector synchronously right after finalizeOperation() returns. So the early path wrote the summary while the failed operation's summarizer was still open.

Fix

#finishSettledEntry now publishes the early result through #produceEarlyResultAsync. That function yields one microtask (await Promise.resolve()) before calling #produceResultAsync. By then the notifying record has closed its summarizer, so the summary contains the full failure tail.

Ordering and per-client correctness don't change:

• entry.finishPromise and the unsubscribe are still set synchronously. Other participants' #needsIteration checks and the batch's #finishEntryAsync (??=) still see the early result as claimed.
• Once unsubscribed, the entry's sink can't receive events from other operations during the yield.
• #produceResultAsync still flushes the sink before writing the result.

rush-lib is not changed.

Tests

• The 3 tests above pass, and their assertions are unchanged.
• New regression test in PhasedRequestSummary.test.ts: "writes the failure summary before an early result while the coalesced batch continues". Client A's selection fails early while client C's operation is held. The test asserts:
  • A's result arrives while the graph is still executing.
  • A's output has the FAILURE banner, the --[ FAILURE: … ]-- section containing the failed operation's output, the duration line, and Operations failed.
  • The result is A's last write.
  • C then succeeds with its own summary.
• Without the fix, the regression test fails.

Linux validation (WSL Ubuntu-24.04, fresh clone of current main @ 7a0348d)

• Before (pristine main): heft test in rush-daemon gave 422 passed, 3 failed (the 3 above).
• After: rush build --to @rushstack/rush-daemon --to @rushstack/rush-cli-client (includes lint) passed, then rush test --only @rushstack/rush-daemon --only @rushstack/rush-cli-client:
  • rush-daemon: 426/426 passed
  • rush-cli-client: 275/275 passed

Optional follow-ups

• In rush-lib, consider closing stdioSummarizer/problemCollector before finalizeOperation() notifies observers. Any onOperationCompleted observer could then read a finished report synchronously.

This came out of the automated rushd Linux analysis (Rushd Hive, bugs 15 and 38). It unblocks #6065, #6066 and #6069.

[Copilot]

Copilot review overview

🟢 Approval recommended

The focused deferral correctly follows synchronous finalization ordering and has targeted regression coverage.

Review effort: Balanced
Findings: None

What changed in this PR

Fixes a race where early coalesced results generated failure summaries before operation output summarizers closed.

Changes:

• Defers early result generation by one microtask.
• Adds regression coverage for complete early failure summaries.
• Records a patch change for @rushstack/rush-daemon.

File	Description
libraries/​rush-daemon/​src/​PhasedRequestRouter.ts	Defers early summary generation until finalization completes.
libraries/​rush-daemon/​src/​test/​PhasedRequestSummary.test.ts	Tests early failure summary completeness and ordering.
common/​changes/​@rushstack/​rush-daemon/​fix-main-summary-race_2026-09-24-21-45.json	Adds the patch changelog entry.

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