Fix KeyError when errors is not iterable (#359)

Author: leszekhanusz

gql/client.py

@@ -34,6 +34,7 @@
 from .utilities import build_client_schema
 from .utilities import parse_result as parse_result_fn
 from .utilities import serialize_variable_values
+from .utils import str_first_element
 
 """
 Load the appropriate instance of the Literal type
@@ -152,7 +153,8 @@ def _build_schema_from_introspection(self, execution_result: ExecutionResult):
         if execution_result.errors:
             raise TransportQueryError(
                 (
-                    f"Error while fetching schema: {execution_result.errors[0]!s}\n"
+                    "Error while fetching schema: "
+                    f"{str_first_element(execution_result.errors)}\n"
                     "If you don't need the schema, you can try with: "
                     '"fetch_schema_from_transport=False"'
                 ),
@@ -858,7 +860,7 @@ def execute(
         # Raise an error if an error is returned in the ExecutionResult object
         if result.errors:
             raise TransportQueryError(
-                str(result.errors[0]),
+                str_first_element(result.errors),
                 errors=result.errors,
                 data=result.data,
                 extensions=result.extensions,
@@ -1066,7 +1068,7 @@ async def subscribe(
                 # Raise an error if an error is returned in the ExecutionResult object
                 if result.errors:
                     raise TransportQueryError(
-                        str(result.errors[0]),
+                        str_first_element(result.errors),
                         errors=result.errors,
                         data=result.data,
                         extensions=result.extensions,
@@ -1229,7 +1231,7 @@ async def execute(
         # Raise an error if an error is returned in the ExecutionResult object
         if result.errors:
             raise TransportQueryError(
-                str(result.errors[0]),
+                str_first_element(result.errors),
                 errors=result.errors,
                 data=result.data,
                 extensions=result.extensions,

gql/utils.py

@@ -1,6 +1,6 @@
 """Utilities to manipulate several python objects."""
 
-from typing import Any, Dict, Tuple, Type
+from typing import Any, Dict, List, Tuple, Type
 
 
 # From this response in Stackoverflow
@@ -47,3 +47,12 @@ def recurse_extract(path, obj):
     nulled_variables = recurse_extract("variables", variables)
 
     return nulled_variables, files
+
+
+def str_first_element(errors: List) -> str:
+    try:
+        first_error = errors[0]
+    except (KeyError, TypeError):
+        first_error = errors
+
+    return str(first_error)

tests/test_aiohttp.py

@@ -199,18 +199,21 @@ async def handler(request):
         assert "500, message='Internal Server Error'" in str(exc_info.value)
 
 
-query1_server_error_answer = '{"errors": ["Error 1", "Error 2"]}'
+transport_query_error_responses = [
+    '{"errors": ["Error 1", "Error 2"]}',
+    '{"errors": {"error_1": "Something"}}',
+    '{"errors": 5}',
+]
 
 
 @pytest.mark.asyncio
-async def test_aiohttp_error_code(event_loop, aiohttp_server):
+@pytest.mark.parametrize("query_error", transport_query_error_responses)
+async def test_aiohttp_error_code(event_loop, aiohttp_server, query_error):
     from aiohttp import web
     from gql.transport.aiohttp import AIOHTTPTransport
 
     async def handler(request):
-        return web.Response(
-            text=query1_server_error_answer, content_type="application/json"
-        )
+        return web.Response(text=query_error, content_type="application/json")
 
     app = web.Application()
     app.router.add_route("POST", "/", handler)