Prevent infinite recursion for unspeakable chars

source/speech/manager.py

@@ -333,7 +333,7 @@ def ensureEndUtterance(seq: SpeechSequence):
 			else:
 				lastOutSeq = outSeqs[-1] if outSeqs else None
 			lastCommand = lastOutSeq[-1] if lastOutSeq else None
-			if not lastCommand or isinstance(lastCommand, (EndUtteranceCommand, ConfigProfileTriggerCommand)):
+			if lastCommand is None or isinstance(lastCommand, (EndUtteranceCommand, ConfigProfileTriggerCommand)):
 				# It doesn't make sense to start with or repeat EndUtteranceCommands.
 				# We also don't want an EndUtteranceCommand immediately after a ConfigProfileTriggerCommand.
 				return
@@ -458,13 +458,18 @@ def _buildNextUtterance(self):
 		# apply any parameters changed before the preemption.
 		params = self._curPriQueue.paramTracker.getChanged()
 		utterance.extend(params)
-		for seq in self._curPriQueue.pendingSequences:
+		lastSequenceIndexAddedToUtterance = None
+		for seqIndex, seq in enumerate(self._curPriQueue.pendingSequences):
 			if isinstance(seq[0], EndUtteranceCommand):
 				# The utterance ends here.
 				break
 			utterance.extend(seq)
+			lastSequenceIndexAddedToUtterance = seqIndex
 		# if any items are cancelled, cancel the whole utterance.
 		if utterance and not self._checkForCancellations(utterance):
+			log.error(f"Checking for cancellations failed, cancelling sequence: {utterance}")
+			# Avoid infinite recursion by removing the problematic sequences:
+			del self._curPriQueue.pendingSequences[:lastSequenceIndexAddedToUtterance + 1]
 			return self._buildNextUtterance()
 		return utterance
 
@@ -542,7 +547,7 @@ def _getMostRecentlyCancelledUtterance(self) -> Optional[_IndexT]:
 		)
 		for index in cancelledIndexes:
 			if (
-				not latestCancelledUtteranceIndex
+				latestCancelledUtteranceIndex is None
 				or self._isIndexABeforeIndexB(latestCancelledUtteranceIndex, index)
 			):
 				latestCancelledUtteranceIndex = index

tests/unit/test_speechManager/__init__.py

@@ -1139,12 +1139,15 @@ def setUp(self):
 		config.conf['featureFlag']['cancelExpiredFocusSpeech'] = 1  # yes
 
 
-class Test_pr11651(unittest.TestCase):
+class RegressionTests(unittest.TestCase):
+	"""Tests to prevent regressions after issues are fixed.
+	"""
 
 	def test_redundantSequenceAfterEndUtterance(self):
 		"""
 		Tests that redundant param change and index commands are not emitted as an extra utterance
 		when the preceeding utterance contained param change commands and an EndUtterance command.
+		See PR #11651
 		E.g. speaking a character.
 		"""
 		smi = SpeechManagerInteractions(self)
@@ -1168,3 +1171,28 @@ def test_redundantSequenceAfterEndUtterance(self):
 			smi.indexReached(1)
 			smi.doneSpeaking()
 			smi.pumpAll()
+
+	def test_nonSpokenCharacter(self):
+		"""Test for fix to GH#11752 - NVDA Freeze with unicode value U+000B
+		Actually, the speech manager receives an empty string for the character U+000B. NVDA
+		does not have a mapping for this character.
+		It is questionable whether we should send anything to the synth when there is no content, however
+		what constitutes 'content' is currently not easy to define.
+		"""
+		smi = SpeechManagerInteractions(self)
+
+		speechSequence = [
+			CharacterModeCommand(True),
+			'',
+			smi.create_EndUtteranceCommand(expectedToBecomeIndex=1)
+		]
+		with smi.expectation():
+			seqIndexes = smi.speak(speechSequence)
+			smi.expect_synthSpeak(seqIndexes)
+
+
+class RegressionTests_withCancellableSpeechEnabled(RegressionTests):
+	"""Note, while cancellable speech is configurable test with and without it enabled."""
+	def setUp(self):
+		super().setUp()
+		config.conf['featureFlag']['cancelExpiredFocusSpeech'] = 1  # yes