Only allow DjangoObjectTypes to DjangoListField

graphene_django/fields.py

@@ -1,13 +1,12 @@
 from functools import partial
 
 from django.db.models.query import QuerySet
-from graphene import NonNull
+from graphql_relay.connection.arrayconnection import connection_from_list_slice
-
 from promise import Promise
 
-from graphene.types import Field, List
+from graphene import NonNull
 from graphene.relay import ConnectionField, PageInfo
-from graphql_relay.connection.arrayconnection import connection_from_list_slice
+from graphene.types import Field, List
 
 from .settings import graphene_settings
 from .utils import maybe_queryset
@@ -15,6 +14,15 @@ from .utils import maybe_queryset
 
 class DjangoListField(Field):
     def __init__(self, _type, *args, **kwargs):
+        from .types import DjangoObjectType
+
+        if isinstance(_type, NonNull):
+            _type = _type.of_type
+
+        assert issubclass(
+            _type, DjangoObjectType
+        ), "DjangoListField only accepts DjangoObjectType types"
+
         # Django would never return a Set of None  vvvvvvv
         super(DjangoListField, self).__init__(List(NonNull(_type)), *args, **kwargs)
 

graphene_django/tests/test_fields.py

@@ -1,5 +1,6 @@
 import pytest
-from graphene import ObjectType, Schema
+
+from graphene import List, NonNull, ObjectType, Schema, String
 
 from ..fields import DjangoListField
 from ..types import DjangoObjectType
@@ -8,6 +9,25 @@ from .models import Reporter as ReporterModel
 
 @pytest.mark.django_db
 class TestDjangoListField:
+    def test_only_django_object_types(self):
+        class TestType(ObjectType):
+            foo = String()
+
+        with pytest.raises(AssertionError):
+            list_field = DjangoListField(TestType)
+
+    def test_non_null_type(self):
+        class Reporter(DjangoObjectType):
+            class Meta:
+                model = ReporterModel
+                fields = ("first_name",)
+
+        list_field = DjangoListField(NonNull(Reporter))
+
+        assert isinstance(list_field.type, List)
+        assert isinstance(list_field.type.of_type, NonNull)
+        assert list_field.type.of_type.of_type is Reporter
+
     def test_get_django_model(self):
         class Reporter(DjangoObjectType):
             class Meta: