build_client_schema: add dev check for invalid introspection argument

Replicates graphql/graphql-js@91d673f

Author: Cito

README.md

@@ -13,7 +13,7 @@ a query language for APIs created by Facebook.
 [![Code Style](https://img.shields.io/badge/code%20style-black-000000.svg)](https://github.com/ambv/black)
 
 The current version 1.0.5 of GraphQL-core-next is up-to-date with GraphQL.js version
-14.3.1. All parts of the API are covered by an extensive test suite of currently 1822
+14.3.1. All parts of the API are covered by an extensive test suite of currently 1823
 unit tests.
 
 

graphql/utilities/build_client_schema.py

@@ -51,6 +51,15 @@ def build_client_schema(
     This function expects a complete introspection result. Don't forget to check the
     "errors" field of a server response before calling this function.
     """
+    if not isinstance(introspection, dict) or not isinstance(
+        introspection.get("__schema"), dict
+    ):
+        raise TypeError(
+            "Invalid or incomplete introspection result. Ensure that you"
+            " are passing the 'data' attribute of an introspection response"
+            " and no 'errors' were returned alongside: " + inspect(introspection)
+        )
+
     # Get the schema from the introspection result.
     schema_introspection = introspection["__schema"]
 

tests/utilities/test_build_client_schema.py

@@ -487,6 +487,27 @@ def describe_throws_when_given_invalid_introspection():
             """
         )
 
+        def throws_when_introspection_is_missing_schema_property():
+            with raises(TypeError) as exc_info:
+                # noinspection PyTypeChecker
+                build_client_schema(None)  # type: ignore
+
+            assert str(exc_info.value) == (
+                "Invalid or incomplete introspection result. Ensure that you"
+                " are passing the 'data' attribute of an introspection response"
+                " and no 'errors' were returned alongside: None"
+            )
+
+            with raises(TypeError) as exc_info:
+                # noinspection PyTypeChecker
+                build_client_schema({})  # type: ignore
+
+            assert str(exc_info.value) == (
+                "Invalid or incomplete introspection result. Ensure that you"
+                " are passing the 'data' attribute of an introspection response"
+                " and no 'errors' were returned alongside: {}"
+            )
+
         def throws_when_referenced_unknown_type():
             introspection = introspection_from_schema(dummy_schema)