Support IAccessible2 labelled-by relation

source/IAccessibleHandler/types.py

@@ -29,3 +29,4 @@ class RelationType(str, enum.Enum):
 	CONTROLLER_FOR = "controllerFor"
 	ERROR = "error"
 	ERROR_FOR = "errorFor"
+	LABELLED_BY = "labelledBy"

source/NVDAObjects/IAccessible/__init__.py

@@ -1163,12 +1163,19 @@ def isPointInObject(self, x, y):
 		return True
 
 	def _get_labeledBy(self):
+		label = self._getIA2RelationFirstTarget(IAccessibleHandler.RelationType.LABELLED_BY)
+		if label:
+			return label
+
 		try:
-			(pacc, accChild) = IAccessibleHandler.accNavigate(
+			ret = IAccessibleHandler.accNavigate(
 				self.IAccessibleObject,
 				self.IAccessibleChildID,
 				IAccessibleHandler.NAVRELATION_LABELLED_BY,
 			)
+			if not ret:
+				return None
+			(pacc, accChild) = ret
 			obj = IAccessible(IAccessibleObject=pacc, IAccessibleChildID=accChild)
 			return obj
 		except COMError:

user_docs/en/changes.md

@@ -70,6 +70,7 @@ Specifically, MathML inside of span and other elements that have the attribute `
 * Opening the NVDA Python Console will no longer fail in case an error occurs while retrieving snapshot variables. (#17391, @CyrilleB79)
 * In Notepad and other UIA documents on Windows 11, if the last line is empty, the `braille next line command` will move the cursor to the last line.
 In any document, if the cursor is on the last line, it will be moved to the end when using this command. (#17251, @nvdaes)
+* In NVDA's Python console, retrieving the "labeledBy" property now works for objects in applications implementing the "labelled-by" IAccessible2 relation and no longer triggers an error. (#17436, @michaelweghorn)
 
 ### Changes for Developers