Fix AssertionError when a queued engine command is cancelled before starting - #1206
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Mukller wants to merge 2 commits into
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Fix AssertionError when a queued engine command is cancelled before starting#1206Mukller wants to merge 2 commits into
Mukller wants to merge 2 commits into
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Protocol.communicate() replaces a still-pending next_command by calling set_finished() on it. If that command had never left the NEW state (its awaiting task was cancelled before the previous command finished), the assertion in set_finished() raised AssertionError: CommandState.NEW, crashing the engine task (niklasf#1116). Allow CommandState.NEW in set_finished(): nothing was sent to the engine while the command was queued, so there is no active phase to unwind - surface the usual EngineError on its result instead. Also guard finished.set_result(), since communicate() cancels the finished future right before calling set_finished().
Python 3.14 removed implicit event-loop creation, so constructing BaseCommand outside a running loop raised RuntimeError.
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Root cause
In
Protocol.communicate(), a still-pendingnext_commandis replaced by cancelling its futures and callingset_finished()on it. If the awaiting task was cancelled before that queued command ever becameACTIVE(two position updates arriving in quick succession, exactly as in #1116), the command is still in stateCommandState.NEWand the assertion inset_finished()raises:Nothing has been sent to the engine while a command sits in the queue, so there is no active phase to unwind — finishing it cleanly is safe.
Changes
BaseCommand.set_finished()now acceptsCommandState.NEW(queued-but-never-started commands) alongsideACTIVE/CANCELLING. A pending result still gets the usualEngineError("engine command finished before returning result"); an already-cancelled result stays cancelled.finished.set_result()with a done-check:communicate()cancels thefinishedfuture immediately before callingset_finished(), so on this path the future can already be cancelled — the previous unconditionalset_result(None)would have raisedInvalidStateErrornext.EngineTestCase: cancelled-while-queued (the AssertionError is thrown if async analysis is cancelled too soon #1116 scenario) and replaced-while-pending (EngineError surfaced on result).Fixes #1116
Testing
python -m pytest test.py::EngineTestCase→ 27 passed, 11 skipped (binary-gated), including the two new regression tests