fix(execution): assume no async iterables in execute_sync

src/graphql/execution/execute.py

@@ -465,6 +465,14 @@ def assume_not_awaitable(_value: Any) -> TypeGuard[Awaitable]:
     return False
 
 
+def assume_not_async_iterable(_value: Any) -> TypeGuard[AsyncIterable]:
+    """Replacement for is_async_iterable if everything is assumed to be synchronous.
+
+    :meta private:
+    """
+    return False
+
+
 def execute_sync(
     schema: GraphQLSchema,
     document: DocumentNode,
@@ -549,6 +557,7 @@ def execute_sync(
         if callable(check_sync)
         else (None if check_sync else assume_not_awaitable)
     )
+    is_async_iterable = assume_not_async_iterable if not check_sync else None
 
     result = experimental_execute_incrementally(
         schema,
@@ -565,6 +574,7 @@ def execute_sync(
         middleware,
         executor_class,
         is_awaitable,
+        is_async_iterable,
         hide_suggestions=hide_suggestions,
         abort_signal=abort_signal,
         hooks=hooks,

tests/execution/test_sync.py

@@ -4,7 +4,13 @@
 from graphql.execution import execute, execute_sync
 from graphql.language import parse
 from graphql.pyutils import is_awaitable
-from graphql.type import GraphQLField, GraphQLObjectType, GraphQLSchema, GraphQLString
+from graphql.type import (
+    GraphQLField,
+    GraphQLList,
+    GraphQLObjectType,
+    GraphQLSchema,
+    GraphQLString,
+)
 from graphql.validation import validate
 
 from ..fixtures import cleanup
@@ -36,6 +42,29 @@ async def _resolve_async(root_value, _info):
         ),
     )
 
+    list_schema = GraphQLSchema(
+        GraphQLObjectType(
+            "Query",
+            {
+                "listField": GraphQLField(
+                    GraphQLList(GraphQLString), resolve=_resolve_sync
+                )
+            },
+        )
+    )
+
+    class _SyncAndAsyncIterable:
+        """An iterable that is also an async iterable, like a Django QuerySet."""
+
+        def __iter__(self):
+            return iter(["sync"])
+
+        def __aiter__(self):
+            return self
+
+        async def __anext__(self):  # pragma: no cover
+            raise StopAsyncIteration
+
     def does_not_return_an_awaitable_for_initial_errors():
         doc = "fragment Example on Query { syncField }"
         assert execute(schema, parse(doc), "rootValue") == (
@@ -156,6 +185,47 @@ async def throws_if_encountering_async_iterable_execution_without_check_sync():
             del exc_info
             cleanup()
 
+        def iterates_sync_and_async_iterables_synchronously_without_check_sync():
+            doc = "query Example { listField }"
+            result = execute_sync(
+                list_schema, document=parse(doc), root_value=_SyncAndAsyncIterable()
+            )
+            assert result == ({"listField": ["sync"]}, None)
+
+        async def throws_if_encountering_sync_and_async_iterable_with_check_sync():
+            doc = "query Example { listField }"
+            with pytest.raises(RuntimeError) as exc_info:
+                execute_sync(
+                    list_schema,
+                    document=parse(doc),
+                    root_value=_SyncAndAsyncIterable(),
+                    check_sync=True,
+                )
+            msg = str(exc_info.value)
+            assert msg == "GraphQL execution failed to complete synchronously."
+            del exc_info
+            cleanup()
+
+        def reports_async_iterables_as_errors_without_check_sync():
+            async def _async_iterable():
+                yield "async"  # pragma: no cover
+
+            doc = "query Example { listField }"
+            result = execute_sync(
+                list_schema, document=parse(doc), root_value=_async_iterable()
+            )
+            assert result == (
+                {"listField": None},
+                [
+                    {
+                        "message": "Expected Iterable, but did not find one"
+                        " for field 'Query.listField'.",
+                        "locations": [(1, 17)],
+                        "path": ["listField"],
+                    }
+                ],
+            )
+
     def describe_graphql_sync():
         def reports_errors_raised_during_schema_validation():
             bad_schema = GraphQLSchema()