Check for errors during client.fetch_schema()

gql/client.py

@@ -802,6 +802,15 @@ def fetch_schema(self) -> None:
         Don't use this function and instead set the fetch_schema_from_transport
         attribute to True"""
         execution_result = self.transport.execute(parse(get_introspection_query()))
+
+        if execution_result.errors:
+            raise TransportQueryError(
+                f"Error while fetching schema: {execution_result.errors[0]!s}",
+                errors=execution_result.errors,
+                data=execution_result.data,
+                extensions=execution_result.extensions,
+            )
+
         self.client.introspection = execution_result.data
         self.client.schema = build_client_schema(self.client.introspection)
 
@@ -1175,6 +1184,15 @@ async def fetch_schema(self) -> None:
         execution_result = await self.transport.execute(
             parse(get_introspection_query())
         )
+
+        if execution_result.errors:
+            raise TransportQueryError(
+                f"Error while fetching schema: {execution_result.errors[0]!s}",
+                errors=execution_result.errors,
+                data=execution_result.data,
+                extensions=execution_result.extensions,
+            )
+
         self.client.introspection = execution_result.data
         self.client.schema = build_client_schema(self.client.introspection)
 

tests/test_aiohttp.py

@@ -1190,3 +1190,46 @@ async def handler(request):
         africa = continents[0]
 
         assert africa["code"] == "AF"
+
+
+@pytest.mark.asyncio
+async def test_aiohttp_error_fetching_schema(event_loop, aiohttp_server):
+    from aiohttp import web
+    from gql.transport.aiohttp import AIOHTTPTransport
+
+    error_answer = """
+{
+    "errors": [
+        {
+            "errorType": "UnauthorizedException",
+            "message": "Permission denied"
+        }
+    ]
+}
+"""
+
+    async def handler(request):
+        return web.Response(
+            text=error_answer,
+            content_type="application/json",
+        )
+
+    app = web.Application()
+    app.router.add_route("POST", "/", handler)
+    server = await aiohttp_server(app)
+
+    url = server.make_url("/")
+
+    transport = AIOHTTPTransport(url=url, timeout=10)
+
+    with pytest.raises(TransportQueryError) as exc_info:
+        async with Client(transport=transport, fetch_schema_from_transport=True):
+            pass
+
+    expected_error = (
+        "Error while fetching schema: "
+        "{'errorType': 'UnauthorizedException', 'message': 'Permission denied'}"
+    )
+
+    assert expected_error in str(exc_info.value)
+    assert transport.session is None

tests/test_requests.py

@@ -755,3 +755,52 @@ def test_code():
                     f2.close()
 
     await run_sync_test(event_loop, server, test_code)
+
+
+@pytest.mark.aiohttp
+@pytest.mark.asyncio
+async def test_requests_error_fetching_schema(
+    event_loop, aiohttp_server, run_sync_test
+):
+    from aiohttp import web
+    from gql.transport.requests import RequestsHTTPTransport
+
+    error_answer = """
+{
+    "errors": [
+        {
+            "errorType": "UnauthorizedException",
+            "message": "Permission denied"
+        }
+    ]
+}
+"""
+
+    async def handler(request):
+        return web.Response(
+            text=error_answer,
+            content_type="application/json",
+        )
+
+    app = web.Application()
+    app.router.add_route("POST", "/", handler)
+    server = await aiohttp_server(app)
+
+    url = server.make_url("/")
+
+    def test_code():
+        transport = RequestsHTTPTransport(url=url)
+
+        with pytest.raises(TransportQueryError) as exc_info:
+            with Client(transport=transport, fetch_schema_from_transport=True):
+                pass
+
+        expected_error = (
+            "Error while fetching schema: "
+            "{'errorType': 'UnauthorizedException', 'message': 'Permission denied'}"
+        )
+
+        assert expected_error in str(exc_info.value)
+        assert transport.session is None
+
+    await run_sync_test(event_loop, server, test_code)