fix(runtime): a stdin listener keeps the event loop alive without perry-stdlib (#9416); pin the write path #9421 blames - #9439
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…ry-stdlib (PerryTS#9416) A program whose only pending work is a `process.stdin` read exited in ~20 ms with the pipe still open, instead of waiting for input the way Node does for a ref'd stdin handle. Root cause. `process.stdin` reached as an OBJECT — an alias (`const s = process.stdin`), a parameter, or a field — files its listener in perry-runtime's own stdin registries and starts perry-runtime's own fd-0 reader. PerryTS#9399 taught *perry-stdlib's* `js_stdlib_has_active_handles` about those lists. But a program whose only stdlib-flavoured work IS that listener links RUNTIME-ONLY, and then the symbol the generated event loop calls is perry-runtime's `js_stdlib_has_active_handles` trampoline, whose `STDLIB_HAS_ACTIVE_FN` is null — so the stdlib arm that knows about the registries is never reached. Tracing the trampoline shows the listener present (`data=1 end=1 started=true`) and `stdin_listeners_keep_loop_alive() == true` on the very first liveness check and on all sixteen of them, while the trampoline returns 0 every time: registration happened before the check, and the answer was simply never consulted. (The literal `process.stdin.on(...)` spelling is unaffected — codegen lowers it to a readline extern, which pulls perry-stdlib in and reports through `js_readline_has_active`.) The nondeterminism in the report follows from the same fact. The generated loop spins a fixed handful of iterations before it quits — a bare `console.log("hi")` program takes 17 — so whether the bytes land inside that window is a race, which is why the failure reads as 40–60 % with input already buffered and is deterministic once the write is delayed. Fix: the trampoline consults `stdin_listeners_keep_loop_alive()` itself, alongside the other runtime-owned reactors. The registry, the reader and the predicate are all perry-runtime's, so the check belongs there. It is not a pin: the predicate is false with no listeners, false once stdin is detached (`pause`/`unref`/`destroy`), and false again after EOF plus the terminal `'end'`/`'close'` dispatch. The gap fixture drives seven roles in re-spawned children over a real pipe, with the payload written 120 ms in so that "the loop stayed alive" is what is measured. On a compiler built from unfixed `origin/main` four of them lose their entire output (aliased data, stdin-as-parameter, end-only, stdin plus one timer); the last two roles are negative controls that must still exit promptly while the parent holds the pipe open, so a fix that merely pinned the loop open would fail them.
…erryTS#9421) PerryTS#9421 reports a claude-code transcript coming out 1 line where Node writes 5, and attributes it to the session writer's async `insertQueueOperation` → `flush` path: "work enqueued asynchronously and flushed before exit is lost; sync writes land". This fixture is that attribution's test, and it does not hold. Fifteen probes, including this fixture's faithful transliteration of the bundle's own `SessionWriter` — `scheduleDrain()` guarded by `flushTimer`, a `setTimeout(FLUSH_INTERVAL_MS = 100)` that awaits `drainWriteQueue()`, a drain that batches the queue and `await`s `fs.promises.appendFile`, and the direct `appendFileSync` "last-prompt" record the report says is the only survivor — are byte-identical between perry and node 26.5.1, on unfixed `main` as well as after PerryTS#9416. So is `fs.promises.appendFile` fire-and-forget, the callback form, `createWriteStream`, an awaited chain, and a queue fed across nextTick / microtask / timer turns. What DOES reproduce 1-vs-5 is leaving before the 100 ms drain timer fires — and that costs both engines the same four records, which the `writer-exit-early` role pins. The signature therefore says the run ended early, not that a flush was dropped, and the divergence is upstream of the writer. PerryTS#9407's handoff notes the likely upstream: on the unauthenticated path perry's claude-code fails with `Cannot read properties of undefined (reading 'def')` / `terminal_reason: model_error` where node reports `Not logged in` / `authentication_failed` / `terminal_reason: completed`. Tests only; no engine change.
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Included review availability: Your plan provides up to 8 included reviews per hour; 4 remain after this review. 📝 WalkthroughWalkthroughThe change updates runtime-only stdin liveness checks and adds tests for stdin lifecycle behavior. It also adds an asynchronous output fixture that exercises queued writes, stream output, process termination, and transcript scenarios. ChangesStdin loop liveness
Async output flush fixture
Estimated code review effort: 3 (Moderate) | ~25 minutes Merge Risk: ⚪ Minimal · up to The PR adds a localized stdin event-loop liveness fix and regression coverage, while the related output-flush change is parity-tested without changing engine behavior. No actionable merge-blocking risk remains beyond normal checks. Sequence Diagram(s)sequenceDiagram
participant ParentDriver
participant ChildProcess
participant StdinPipe
participant EventLoop
ParentDriver->>ChildProcess: spawn stdin role
ChildProcess->>EventLoop: register process.stdin listener
EventLoop->>EventLoop: check js_stdlib_has_active_handles()
ParentDriver->>StdinPipe: write delayed payload or close pipe
StdinPipe-->>ChildProcess: deliver data or EOF
ChildProcess-->>ParentDriver: report output and exit code
🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
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In `@changelog.d/9421-async-output-flush.md`:
- Around line 3-4: Rewrite the changelog entry as one coherent release note
describing the added parity fixture for the async queue-and-flush write path and
its shipped behavior. Remove the incomplete wording, duplicated issue reference,
and internal attribution discussion.
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| - `test_gap_9421_async_output_flush` pins the async queue-and-flush write path | ||
| #9421 attributes the truncated claude-code transcript to (#9421). It drives |
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Rewrite the malformed changelog entry.
Lines 3-4 form an incomplete sentence and repeat #9421. Describe the added parity fixture as one coherent release-note entry. Remove the internal attribution discussion.
Based on learnings: changelog fragments must describe the final shipped behavior as one coherent release-note entry.
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In `@changelog.d/9421-async-output-flush.md` around lines 3 - 4, Rewrite the
changelog entry as one coherent release note describing the added parity fixture
for the async queue-and-flush write path and its shipped behavior. Remove the
incomplete wording, duplicated issue reference, and internal attribution
discussion.
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One fix and one falsified premise, kept separate.
#9416 — stdin-only programs exit before the read (fixed)
The failing shape is
process.stdinreached as an object —const s = process.stdin, a parameter, a field — not the literalprocess.stdin.on(...)spelling.The literal spelling lowers to perry-stdlib's readline extern, which pulls perry-stdlib into the link and reports through
js_readline_has_active: correct in 10/10 runs. The object spelling files its listener in perry-runtime's own stdin registries and links runtime-only — and thejs_stdlib_has_active_handlessymbol the generated loop calls is then perry-runtime's trampoline incrates/perry-runtime/src/lib.rs, whoseSTDLIB_HAS_ACTIVE_FNis null.#9407 wired
stdin_listeners_keep_loop_alive()into perry-stdlib's copy of that function only, so on a runtime-only link the predicate is unreachable.Which hypothesis this is
The issue proposed two candidates: liveness evaluated before registration, or registration never refs the handle. Env-gated tracing in the trampoline settles it — on a failing run, all 16 liveness checks print:
The listener is present and
started=trueat the first check, so "evaluated too early" is falsified.stdin_keep=trueon every check while the trampoline returns 0 — it is the second and more dangerous case: every handle in that runtime-local registry has the same hole under a runtime-only link.The reported 40–60% flakiness is explained
The generated loop always spins a fixed handful of iterations before quitting — a bare
console.log("hi")takes 17 header checks — so whether the bytes land inside that window is a race. With input already buffered it is a coin flip; with the write delayed 120 ms it fails deterministically, the child exiting in 21–56 ms with the pipe still open.Correcting the issue's suggested direction
#9416 proposes a codegen-side fix ("whether to enter the loop at all"). That is wrong: the loop is entered and its header does call the right symbol — the symbol answers wrongly. The fix is one runtime-side check, placed next to the other runtime-owned reactors (child_process, pty, dgram, ipc, signal). It also repairs
timer.rs::other_event_sources_keep_loop_alive, which consults the same symbol for unref'd timers.Verification
test-files/test_gap_9416_stdin_only_loop_liveness.tsdrives 7 roles in re-spawned children over a real pipe. On a compiler built from unfixedorigin/main, four roles lose their entire output:After the fix it is byte-identical to node 26.5.1. The last two roles (
no-listener,paused) are negative controls: the parent holds the pipe open forever and they must still exit promptly, so a fix that merely pinned the loop open fails them.Unit test
stdin_object_listener_keeps_the_loop_alive_without_stdlib, sabotage-verified — neutering the newifgivesleft: 0, right: 1.#9421 — transcript 1 line vs 5: the async-flush premise does not survive testing
No engine change. 15 probes, ending with a faithful transliteration of the bundle's own
SessionWriter(read out ofcli_2.1.112.js):scheduleDrain()guarded byflushTimer,setTimeout(FLUSH_INTERVAL_MS = 100),await drainWriteQueue(), batchedawait fs.promises.appendFile, alongside the directappendFileSync"last-prompt" record the issue says is the only survivor. Byte-identical between perry and node, before and after — as arefs.promises.appendFilefire-and-forget, the callback form,createWriteStream, an awaited chain, a queue fed across nextTick/microtask/timer turns, the stdout write loop, interleaved log/error, write-then-process.exit(), and 200 KB through a pipe.What does reproduce 1-vs-5 is exiting before the 100 ms drain timer fires — and that costs both engines the same four records. So the signature says the run ended early, not that a flush was dropped: the divergence is upstream of the writer. The likely upstream is #9417 (on the unauthenticated path perry fails with
reading 'def'/model_errorwhere node reportsNot logged in/authentication_failed/completed) — a different, earlier error path both enqueues fewer records and shortens the run below 100 ms. That is a pointer, not a proof: the cc bundle was not run here.test_gap_9421_async_output_flush.tsis committed as a parity-pinning regression test, not a gap test — it passes on unfixed main, and its passing is the evidence. The commit message and changelog both say so. #9402's SIGPIPE fix does not interact.Suites
cargo test -p perry-runtime --lib -- --test-threads=1: 2927 passed, 0 failed, 4 ignored.Parity is a targeted slice, not the full suite — the box was at load 130–145 with six other agents building and the volume hit 100%, making the full 1438-fixture run ~20 h. Filters
stdin, process, exit, timer, timeout, interval, event= 38 unique tests, both toolchains:Exactly one outcome changed:
test_gap_9416_stdin_only_loop_livenessparity_fail → pass. The 5 compile-fails are identical on both sides, a harness artifact ofPERRY_SKIP_BUILD=1. All 8 fixtures touchingprocess.stdinare inside this slice. The full suite still wants a run on a quiet host.Summary by CodeRabbit
Bug Fixes
process.stdininput now remain active until input arrives or the stream is properly closed.Tests