Add tests for iterator close semantics of Array.fromAsync - #5095
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The existing fromAsync tests cover that an abrupt mapper completion closes the iterator, but not the surrounding close semantics: - a normal completion (done: true) must not call return() - the close is awaited: the promise from return() settles before the promise returned by Array.fromAsync is rejected - when both the mapper and return() fail, the promise rejects with the mapper's error (AsyncIteratorClose returns the original completion) These distinguish implementations today: quickjs-ng closed exhausted iterators without awaiting, and V8 never settles the returned promise when return() throws or rejects during an abrupt close.
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The existing
Array.fromAsynctests cover that an abrupt mapper completion closes the iterator (mapfn-*-throws-close-*-iterator.js), but not the surrounding close semantics:does-not-close-exhausted-async-iterator.js/does-not-close-exhausted-sync-iterator.js: a normal completion (done: true) must not callreturn(); iteration ends with a return completion, never AsyncIteratorClose.mapfn-throws-close-async-iterator-awaited.js: the close is awaited, so the promise fromreturn()settles before the promise returned byArray.fromAsyncis rejected (AsyncIteratorClose step 5.d).mapfn-throws-close-rejection-not-masked.js: when both the mapper andreturn()fail, the promise rejects with the mapper's error (AsyncIteratorClose step 6 returns the original completion).These distinguish implementations today: quickjs-ng closed exhausted iterators without awaiting the result (fix in quickjs-ng/quickjs#1596, which prompted these tests), and V8 (Node 24.14) never settles the returned promise at all when
return()throws or rejects during an abrupt close, so the last test currently hangs there.