fix(generators): reject pending promises to prevent runtime deadlock #115
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… deadlock When using Observable runtime v6.0.0+, generators with undefined initial values would deadlock when their upstream dependencies changed. The runtime waits for the old generator to settle before starting the new one, but the pending promise would never resolve. The fix converts observe() from an async function* to a manual async iterator, allowing return() to immediately reject pending promises without waiting for them to settle first. Adds unit test for promise rejection and integration test reproducing the deadlock scenario with Generators.input and the Observable runtime.
tomlarkworthy
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tomlarkworthy
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mbostock
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Nice, thank you! 👍 This looks about right to me! I’ll probably make some style changes. I agree we need to opt-out of the async generator function so that we can reject the pending promise when the generator is return’ed or throw’ed.
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mbostock
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I fixed up Generators.queue, too.
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When using Observable runtime v6.0.0+, generators with undefined initial values would deadlock when their upstream dependencies changed. The runtime waits for the old generator to settle before starting the new one, but the pending promise would never resolve.
The fix converts observe() from an async function* to a manual async iterator, allowing return() to immediately reject pending promises without waiting for them to settle first.
port of observablehq/stdlib#399, addresses issue raised here observablehq/runtime#376