fix: Return null on empty files/images

Fix #453

strawberry_django/fields/field.py

@@ -18,6 +18,7 @@
 from asgiref.sync import sync_to_async
 from django.core.exceptions import ObjectDoesNotExist
 from django.db import models
+from django.db.models.fields.files import FileDescriptor
 from django.db.models.fields.related import (
     ForwardManyToOneDescriptor,
     ReverseManyToOneDescriptor,
@@ -202,7 +203,14 @@ def get_result(
                     # Reversed OneToOne will raise ObjectDoesNotExist when
                     # trying to access it if the relation doesn't exist.
                     except_as_none=(ObjectDoesNotExist,) if self.is_optional else None,
+                    empty_file_descriptor_as_null=True,
                 )
+            else:
+                # FileField/ImageField will always return a FileDescriptor, even when the
+                # field is "null". If it is falsy (i.e. doesn't have a file) we should
+                # return `None` instead.
+                if isinstance(attr, FileDescriptor) and not result:
+                    result = None
 
         if is_awaitable:
 

strawberry_django/resolvers.py

@@ -7,6 +7,7 @@
 
 from asgiref.sync import sync_to_async
 from django.db import models
+from django.db.models.fields.files import FileDescriptor
 from django.db.models.manager import BaseManager
 from strawberry.utils.inspect import in_async_context
 from typing_extensions import ParamSpec
@@ -127,6 +128,7 @@ def django_getattr(
     *,
     qs_hook: Callable[[models.QuerySet[_M]], Any] = default_qs_hook,
     except_as_none: tuple[type[Exception], ...] | None = None,
+    empty_file_descriptor_as_null: bool = False,
 ) -> AwaitableOrValue[Any]: ...
 
 
@@ -138,6 +140,7 @@ def django_getattr(
     *,
     qs_hook: Callable[[models.QuerySet[_M]], Any] = default_qs_hook,
     except_as_none: tuple[type[Exception], ...] | None = None,
+    empty_file_descriptor_as_null: bool = False,
 ) -> AwaitableOrValue[Any]: ...
 
 
@@ -148,10 +151,29 @@ def django_getattr(
     *,
     qs_hook: Callable[[models.QuerySet[_M]], Any] = default_qs_hook,
     except_as_none: tuple[type[Exception], ...] | None = None,
+    empty_file_descriptor_as_null: bool = False,
 ):
-    args = (default,) if default is not _SENTINEL else ()
-    return django_resolver(getattr, qs_hook=qs_hook, except_as_none=except_as_none)(
+    return django_resolver(
+        _django_getattr,
+        qs_hook=qs_hook,
+        except_as_none=except_as_none,
+    )(
         obj,
         name,
-        *args,
+        default,
+        empty_file_descriptor_as_null=empty_file_descriptor_as_null,
     )
+
+
+def _django_getattr(
+    obj: Any,
+    name: str,
+    default: Any = _SENTINEL,
+    *,
+    empty_file_descriptor_as_null: bool = False,
+):
+    args = (default,) if default is not _SENTINEL else ()
+    result = getattr(obj, name, *args)
+    if empty_file_descriptor_as_null and isinstance(result, FileDescriptor):
+        result = None
+    return result

tests/test_queries.py

@@ -1,9 +1,13 @@
+import io
 import textwrap
 from typing import List, Optional, cast
 
 import pytest
 import strawberry
+from asgiref.sync import sync_to_async
+from django.core.files.uploadedfile import SimpleUploadedFile
 from graphql import GraphQLError
+from PIL import Image
 from strawberry import auto
 
 import strawberry_django
@@ -31,6 +35,13 @@ class Group:
     users: List[User]
 
 
+@strawberry_django.type(models.Fruit)
+class Fruit:
+    id: auto
+    name: auto
+    picture: auto
+
+
 @strawberry_django.type(models.Fruit)
 class BerryFruit:
     id: auto
@@ -62,6 +73,7 @@ class Query:
     users: List[User] = strawberry_django.field()
     group: Group = strawberry_django.field()
     groups: List[Group] = strawberry_django.field()
+    fruit: Fruit = strawberry_django.field()
     berries: List[BerryFruit] = strawberry_django.field()
     bananas: List[BananaFruit] = strawberry_django.field()
 
@@ -155,6 +167,67 @@ async def test_model_properties(query, fruits):
     ]
 
 
+async def test_query_file_field(query):
+    img_f = io.BytesIO()
+    img = Image.new(mode="RGB", size=(1, 1), color="red")
+    img.save(img_f, format="jpeg")
+    upload = SimpleUploadedFile("strawberry-picture.png", img_f.getvalue())
+    fruit = await sync_to_async(models.Fruit.objects.create)(
+        name="Strawberry",
+        picture=upload,
+    )
+
+    result = await query(
+        """\
+        query Fruit ($pk: ID!) {
+         fruit (pk: $pk) {
+           id
+           name
+           picture {
+             name
+           }
+         }
+        }
+        """,
+        {"pk": fruit.pk},
+    )
+
+    assert not result.errors
+    assert result.data is not None
+    assert result.data["fruit"] == {
+        "id": str(fruit.pk),
+        "name": "Strawberry",
+        "picture": {"name": ".tmp_upload/strawberry-picture.png"},
+    }
+
+
+async def test_query_file_field_when_null(query):
+    fruit = await sync_to_async(models.Fruit.objects.create)(name="Strawberry")
+
+    result = await query(
+        """\
+        query Fruit ($pk: ID!) {
+         fruit (pk: $pk) {
+           id
+           name
+           picture {
+             name
+           }
+         }
+        }
+        """,
+        {"pk": fruit.pk},
+    )
+
+    assert not result.errors
+    assert result.data is not None
+    assert result.data["fruit"] == {
+        "id": str(fruit.pk),
+        "name": "Strawberry",
+        "picture": None,
+    }
+
+
 def test_field_name():
     """Make sure that field_name overriding is not ignored."""