Make detection of not supported languages more robust

source/synthDriverHandler.py

@@ -344,15 +344,21 @@ def languageIsSupported(self, lang: str | None) -> bool:
 		"""
 		if lang is None:
 			return True
+		normalizedLang = languageHandler.normalizeLanguage(lang)
+		if normalizedLang is None:
+			return False
+		rootLang = normalizedLang.split("_")[0]
+		normalizedAvailableLangs: set[str] = set()
 		for availableLang in self.availableLanguages:
-			if availableLang is not None and (
-				lang == languageHandler.normalizeLanguage(availableLang)
-				or lang == languageHandler.normalizeLanguage(availableLang).split("_")[0]
-			):
-				return True
-		rootLang = languageHandler.normalizeLanguage(lang).split("_")[0]
-		fallbackLang = f"{rootLang}-{rootLang}"
-		if fallbackLang in self.availableLanguages:
+			if availableLang is None:
+				continue
+			normalizedAvailableLang = languageHandler.normalizeLanguage(availableLang)
+			if normalizedAvailableLang is None:
+				continue
+			normalizedAvailableLangs.add(normalizedAvailableLang)
+		if normalizedLang in normalizedAvailableLangs:
+			return True
+		if any(rootLang == availableLang.split("_")[0] for availableLang in normalizedAvailableLangs):
 			return True
 		return False
 

tests/unit/test_synthDriverHandler.py

@@ -132,3 +132,39 @@ def test_synthChangedExtensionPoint(self):
 			**expectedKwargs,
 		):
 			synthDriverHandler.setSynth("auto")
+
+
+class TestLanguageIsSupported(unittest.TestCase):
+	def setUp(self) -> None:
+		self._synth = MockSynth(FAKE_DEFAULT_SYNTH_NAME)
+		self._synth.availableLanguages = set()
+
+	def tearDown(self) -> None:
+		del self._synth
+
+	def _languageIsSupported(self, lang: str | None) -> bool:
+		return synthDriverHandler.SynthDriver.languageIsSupported(self._synth, lang)
+
+	def test_noneLanguageIsSupported(self):
+		self._synth.availableLanguages = {"en_US"}
+		self.assertTrue(self._languageIsSupported(None))
+
+	def test_normalizedExactLanguageMatch(self):
+		self._synth.availableLanguages = {"en_US"}
+		self.assertTrue(self._languageIsSupported("en-us"))
+
+	def test_rootLanguageMatch(self):
+		self._synth.availableLanguages = {"en_GB"}
+		self.assertTrue(self._languageIsSupported("en"))
+
+	def test_unsupportedLanguage(self):
+		self._synth.availableLanguages = {"en_US"}
+		self.assertFalse(self._languageIsSupported("fr"))
+
+	def test_metaAndNoneAvailableLanguagesIgnored(self):
+		self._synth.availableLanguages = {None, "x-western", "en_US"}
+		self.assertTrue(self._languageIsSupported("en"))
+
+	def test_metaInputLanguageNotSupported(self):
+		self._synth.availableLanguages = {"en_US"}
+		self.assertFalse(self._languageIsSupported("x-western"))

user_docs/en/changes.md

@@ -56,7 +56,7 @@ The setting is disabled by default. (#20013, @LeonarddeR)
 
 ### Bug Fixes
 
-* Fixed an error when a synthesizer doesn't have available languages, and NVDA tries to report if a language is supported. (#20080, @nvdaes)
+* Fixed an error that could occur when NVDA checked whether a language is supported for a synthesizer with invalid languages. (#20080, @nvdaes)
 * NVDA will attempt to recover more quickly from freezes in some applications, especially those written in Java. (#14396, @thgcode)
 * In Firefox browse mode, the accessible name of form controls (such as checkboxes and radio buttons) is now correctly announced when the control has an `aria-label` and an associated `<label>` element that contains only `aria-hidden` content. (#19409, @bramd)
 * The "Toggles on and off if the screen layout is preserved while rendering the document content" item in the "Browse mode" category of the Input Gestures dialog now behaves correctly. (#18378)