[Python] Skip attributes that raise during stable code identifier lambda search

sdks/python/apache_beam/internal/code_object_pickler.py

@@ -176,7 +176,13 @@ def _search_module_or_class(
   rest = qual_name_parts[1:]
   if first_part == '<lambda>':
     for name in dir(node):
-      value = getattr(node, name)
+      try:
+        value = getattr(node, name)
+      except Exception:  # pylint: disable=broad-except
+        # Unrelated attributes (e.g. descriptors that only work on instances,
+        # or lazy module attributes with missing dependencies) can raise when
+        # read. They can't be the lambda we are looking for, so skip them.
+        continue
       if (hasattr(callable, '__code__') and
           isinstance(value, type(callable)) and
           value.__code__ == callable.__code__):

sdks/python/apache_beam/internal/code_object_pickler_test.py

@@ -111,6 +111,19 @@ def process(self):
     return lambda: 1
 
 
+class _InstanceOnlyDescriptor:
+  def __get__(self, instance, owner=None):
+    if instance is None:
+      raise TypeError("only valid on instances")
+    return 1
+
+
+class ClassWithLambdaAndRaisingAttribute:
+  # Sorts before `fn` in dir(), so it is read first during the lambda search.
+  a_setting = _InstanceOnlyDescriptor()
+  fn = lambda self, x: x + 1
+
+
 class ClassWithNestedClass:
   class InnerClass:
     def process(self):
@@ -247,6 +260,16 @@ def test_invalid_lambda_with_hash_path_raises_exception(self):
           "apache_beam.internal.test_data.module_3."
           "my_function.__code__.co_consts[<lambda>, ('',), 1234567890]")
 
+  def test_lambda_search_skips_attributes_that_raise(self):
+    fn = ClassWithLambdaAndRaisingAttribute.fn
+    path = code_object_pickler.get_code_object_identifier(fn)
+    self.assertEqual(
+        path,
+        "apache_beam.internal.code_object_pickler_test."
+        "ClassWithLambdaAndRaisingAttribute.fn.__code__")
+    self.assertEqual(
+        code_object_pickler.get_code_from_identifier(path), fn.__code__)
+
   def test_adding_local_variable_in_class_preserves_object(self):
     self.assertEqual(
         code_object_pickler.get_code_from_identifier(