fix(deno): Handle reader.closed rejection from releaseLock() in streaming#20187
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andreiborza merged 3 commits intodevelopfrom Apr 10, 2026
Merged
fix(deno): Handle reader.closed rejection from releaseLock() in streaming#20187andreiborza merged 3 commits intodevelopfrom
reader.closed rejection from releaseLock() in streaming#20187andreiborza merged 3 commits intodevelopfrom
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…treaming Replace `reader.closed.finally(() => onDone())` with `reader.closed.then(() => onDone(), () => onDone())` in `monitorStream`. Per the WHATWG Streams spec, `reader.releaseLock()` rejects `reader.closed` when the promise is still pending. `.finally()` propagates that rejection as an unhandled promise rejection, while `.then(f, f)` suppresses it by handling both the fulfilled and rejected cases. Closes: #20177
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s1gr1d
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Seems like a good approach - looks good 👍
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Cursor Bugbot has reviewed your changes and found 1 potential issue.
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| e.preventDefault(); | ||
| unhandledRejection = e; | ||
| }; | ||
| globalThis.addEventListener('unhandledrejection', handler); |
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Unhandled rejection listener registered after triggering action
Low Severity
The unhandledrejection event listener is registered on line 46, after reader.releaseLock() on line 39 which is the action that would trigger the rejection. If the fix were ever reverted to .finally(), the unhandled rejection event could fire before the listener is attached, causing the assertEquals(unhandledRejection, undefined, ...) assertion to pass incorrectly — hiding the regression the test is meant to catch. The listener needs to be set up before reader.releaseLock() to reliably detect unhandled rejections. Also, the test uses setTimeout(resolve, 50) which is a sleep-in-test pattern; a more deterministic signal would be preferable.
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This PR replaces
reader.closed.finally(() => onDone())withreader.closed.then(() => onDone(), () => onDone())inmonitorStream.Per the WHATWG Streams spec,
reader.releaseLock()rejectsreader.closedwhen the promise is still pending..finally()propagates that rejection as an unhandled promise rejection, while.then(f, f)suppresses it by handling both the fulfilled and rejected cases.I was not able to reproduce the error directly on my deno version but this should prevent the issue.
Closes: #20177