GraphQLError: keep extensions always present

Replicates graphql/graphql-js@b1ce2c3

Author: Cito

src/graphql/error/graphql_error.py

@@ -161,12 +161,10 @@ def __init__(
                 self.__cause__ = original_error.__cause__
             elif original_error.__context__:
                 self.__context__ = original_error.__context__
-            if not extensions:
-                try:
-                    # noinspection PyUnresolvedReferences
-                    extensions = original_error.extensions  # type: ignore
-                except AttributeError:
-                    pass
+            if extensions is None:
+                original_extensions = getattr(original_error, "extensions", None)
+                if isinstance(original_extensions, dict):
+                    extensions = original_extensions
         self.extensions = extensions or {}
         if not self.__traceback__:
             self.__traceback__ = exc_info()[2]

tests/error/test_graphql_error.py

@@ -39,10 +39,13 @@ def is_a_class_and_is_a_subclass_of_exception():
         assert isinstance(GraphQLError("str"), Exception)
         assert isinstance(GraphQLError("str"), GraphQLError)
 
-    def has_a_name_message_and_stack_trace():
+    def has_a_name_message_extensions_and_stack_trace():
         e = GraphQLError("msg")
         assert e.__class__.__name__ == "GraphQLError"
         assert e.message == "msg"
+        assert e.extensions == {}
+        assert e.__traceback__ is None
+        assert str(e) == "msg"
 
     def uses_the_stack_of_an_original_error():
         try: