Fix SCXML parallel transition domains - #26
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This pull request corrects the SCXML transition-domain resolution by ensuring that the least common compound ancestor (find_lcca) is a compound state. This change resolves the remaining failures in the more-parallel SCXML conformance suite, allowing all 54 configured SCXML test cases to pass. The documentation, changelog, and test suites have been updated to reflect this milestone. I have no additional feedback to provide.
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| """Return the least common compound ancestor for SCXML transition domains.""" | ||
| for anc in get_proper_ancestors(state_list[0], state2=None): | ||
| if all(is_descendent(s, state2=anc) for s in state_list[1:]): | ||
| if is_compound_state(anc) and all( |
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When the machine root is itself type: "parallel", this filter skips that root parallel ancestor, so find_lcca returns None for an external transition declared on a region that targets a descendant such as a.on.RESET -> #a1. The entry-set code then uses ancestor=None and re-enters the machine root, causing root entry actions to run again on every regional reset; through the public Machine.transition path there is no matching root exit because configurations are reconstructed from state.value without the root node. Before this change the root parallel node was the transition domain, so this root-level side effect did not occur.
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Summary
more-parallelfailuresmore-parallelcases into the required SCXML CI subsetRoot Cause
find_lcca()accepted any common ancestor, including a parallel state. For external transitions sourced inside one parallel region, that made the parallel parent the transition domain. The algorithm exited sibling regions but did not re-enter the parallel parent, so those siblings disappeared from the resulting configuration.SCXML requires the least common compound ancestor. Restricting the domain candidate restores parallel entry fan-out and also gives conflict resolution the correct exit sets.
Behavioral Impact
External transitions inside a parallel state may now correctly exit and re-enter the enclosing parallel branch. Affected sibling regions return to their initial states and their exit/entry actions run once. Competing transitions continue to resolve by source depth and document order.
There are no public API or type changes.
Machine(config, ...), snapshot immutability, handler adaptation, and the safe SCXML condition subset are unchanged.Validation
poetry run python -m pytest tests/ --ignore=tests/test_scxml.py— 392 passedpoetry run python -m pytest tests/test_parallel.py tests/test_scxml.py -q— 63 passedpoetry run mypy src/xstate/poetry run ruff format --check src/ tests/poetry run ruff check src/ tests/git diff --checkConformance Scope
The configured SCXML subset is now green, including all enabled
more-parallelcases. This PR does not claim broad W3C datamodel or executable-content conformance; disabled assignment-oriented cases and general JavaScript evaluation remain out of scope.