fix: foreign key nullable and custom resolver (#1446)

* fix: nullable one to one relation

* fix: makefile

Author: superlevure

Diff for: Makefile

@@ -10,7 +10,7 @@ dev-setup:
 
 .PHONY: tests ## Run unit tests
 tests:
-	py.test graphene_django --cov=graphene_django -vv
+	PYTHONPATH=. py.test graphene_django --cov=graphene_django -vv
 
 .PHONY: format ## Format code
 format:

Diff for: graphene_django/converter.py

@@ -302,12 +302,15 @@ def custom_resolver(root, info, **args):
                     reversed_field_name = root.__class__._meta.get_field(
                         field_name
                     ).remote_field.name
-                    return _type.get_queryset(
-                        _type._meta.model.objects.filter(
-                            **{reversed_field_name: root.pk}
-                        ),
-                        info,
-                    ).get()
+                    try:
+                        return _type.get_queryset(
+                            _type._meta.model.objects.filter(
+                                **{reversed_field_name: root.pk}
+                            ),
+                            info,
+                        ).get()
+                    except _type._meta.model.DoesNotExist:
+                        return None
 
                 return custom_resolver
 

Diff for: graphene_django/tests/models.py

@@ -19,7 +19,11 @@ class Pet(models.Model):
 class FilmDetails(models.Model):
     location = models.CharField(max_length=30)
     film = models.OneToOneField(
-        "Film", on_delete=models.CASCADE, related_name="details"
+        "Film",
+        on_delete=models.CASCADE,
+        related_name="details",
+        null=True,
+        blank=True,
     )
 
 

Diff for: graphene_django/tests/test_query.py

@@ -2062,3 +2062,74 @@ def resolve_person(self, info, name):
     assert result.data["person"] == {
         "pets": [{"name": "Jane's dog"}],
     }
+
+
+def test_should_query_nullable_one_to_one_relation_with_custom_resolver():
+    class FilmType(DjangoObjectType):
+        class Meta:
+            model = Film
+
+        @classmethod
+        def get_queryset(cls, queryset, info):
+            return queryset
+
+    class FilmDetailsType(DjangoObjectType):
+        class Meta:
+            model = FilmDetails
+
+        @classmethod
+        def get_queryset(cls, queryset, info):
+            return queryset
+
+    class Query(graphene.ObjectType):
+        film = graphene.Field(FilmType, genre=graphene.String(required=True))
+        film_details = graphene.Field(
+            FilmDetailsType, location=graphene.String(required=True)
+        )
+
+        def resolve_film(self, info, genre):
+            return Film.objects.filter(genre=genre).first()
+
+        def resolve_film_details(self, info, location):
+            return FilmDetails.objects.filter(location=location).first()
+
+    schema = graphene.Schema(query=Query)
+
+    Film.objects.create(genre="do")
+    FilmDetails.objects.create(location="London")
+
+    query_film = """
+        query getFilm($genre: String!) {
+            film(genre: $genre) {
+                genre
+                details {
+                    location
+                }
+            }
+        }
+    """
+
+    query_film_details = """
+        query getFilmDetails($location: String!) {
+            filmDetails(location: $location) {
+                location
+                film {
+                    genre
+                }
+            }
+        }
+    """
+
+    result = schema.execute(query_film, variables={"genre": "do"})
+    assert not result.errors
+    assert result.data["film"] == {
+        "genre": "DO",
+        "details": None,
+    }
+
+    result = schema.execute(query_film_details, variables={"location": "London"})
+    assert not result.errors
+    assert result.data["filmDetails"] == {
+        "location": "London",
+        "film": None,
+    }