Adds the structural alternative to "wait for a downstream symptom and
bisect to find the bad dispatch": catch illegal transitions at the
dispatch boundary instead of letting them silently no-op.
In release mode (default — no env var set):
- Illegal events are dropped silently
- A `log.debug` line is emitted with the state and event type
- dispatch returns []
- state is unchanged
- This is what production runs
In strict mode (BOORU_VIEWER_STRICT_STATE=1):
- Illegal events raise InvalidTransition(state, event)
- The exception carries both fields for the diagnostic
- This is for development and the test suite — it makes
programmer errors loud and immediate instead of silently
cascading into a downstream symptom
The legality map (`_LEGAL_EVENTS_BY_STATE`) is per-state. Most events
(NavigateRequested / Mute / Volume / LoopMode / Fullscreen / window
events / Close / ContentArrived) are globally legal in any non-Closing
state. State-specific events are listed per state. Closing has an
empty legal set; the dispatch entry already drops everything from
Closing before the legality check runs.
The map distinguishes "legal-but-no-op" from "structurally invalid":
- VideoEofReached in LoadingVideo: LEGAL. The state machine
intentionally accepts and drops this event. It's the EOF race
fix — the event arriving in LoadingVideo is the race scenario,
and dropping is the structural cure. Strict mode does NOT raise.
- VideoEofReached in SeekingVideo: LEGAL. Same reasoning — eof
during a seek is stale.
- VideoEofReached in AwaitingContent / DisplayingImage: ILLEGAL.
No video is loaded; an eof event arriving here is a real bug
in either mpv or the adapter. Strict mode raises.
The strict-mode read happens per-dispatch (`os.environ.get`), not
cached at module load, so monkeypatch.setenv in tests works
correctly. The cost is microseconds per dispatch — negligible.
Tests passing after this commit (65 total → 65 pass):
Newly added (3):
- test_strict_mode_raises_invalid_transition
- test_strict_mode_does_not_raise_for_legal_events
- test_strict_mode_legal_but_no_op_does_not_raise
Plus the existing 62 still pass — the legality check is non-
invasive in release mode (existing tests run without
BOORU_VIEWER_STRICT_STATE set, so they see release-mode behavior).
Phase A (16 tests in tests/core/) still green.
The state machine logic is now COMPLETE. Every state, every event,
every effect is implemented with both happy-path transitions and
illegal-transition handling. The remaining commits (12-16) carve
the implementation into the planned file layout (effects.py split,
hyprland.py extraction) and rewire the Qt adapter.
Test cases for commit 12 (effects split):
- Re-import after the file split still works
- All 65 tests still pass after `from .effects import ...` change
pax
3ade3a71c1