Generated fields type resolution

strawberry_django/fields/base.py

@@ -3,6 +3,7 @@
 import functools
 from typing import TYPE_CHECKING, Any, Optional, TypeVar, cast
 
+import django
 from django.db.models import ForeignKey
 from strawberry import LazyType, relay
 from strawberry.annotation import StrawberryAnnotation
@@ -37,6 +38,11 @@
 
 _QS = TypeVar("_QS", bound="models.QuerySet")
 
+if django.VERSION >= (5, 0):
+    from django.db.models import GeneratedField  # type: ignore
+else:
+    GeneratedField = None
+
 
 class StrawberryDjangoFieldBase(StrawberryField):
     def __init__(
@@ -201,8 +207,15 @@ def resolve_type(
                 ),
                 self.origin_django_type,
             )
+
+            is_generated_field = GeneratedField is not None and isinstance(
+                model_field, GeneratedField
+            )
+            field_to_check = (
+                model_field.output_field if is_generated_field else model_field  # type: ignore
+            )
             if is_optional(
-                model_field,
+                field_to_check,
                 self.origin_django_type.is_input,
                 self.origin_django_type.is_partial,
             ):

strawberry_django/fields/types.py

@@ -18,6 +18,7 @@
     Union,
 )
 
+import django
 import strawberry
 from django.core.exceptions import FieldDoesNotExist, ImproperlyConfigured
 from django.db.models import Field, Model, fields
@@ -38,6 +39,12 @@
     IntegerChoicesField = None
     TextChoicesField = None
 
+if django.VERSION >= (5, 0):
+    from django.db.models import GeneratedField  # type: ignore
+else:
+    GeneratedField = None
+
+
 if TYPE_CHECKING:
     from strawberry_django.type import StrawberryDjangoDefinition
 
@@ -469,6 +476,10 @@ def resolve_model_field_type(
                 ),
             )
             model_field._strawberry_enum = field_type  # type: ignore
+    # Generated fields
+    elif GeneratedField is not None and isinstance(model_field, GeneratedField):
+        model_field_type = type(model_field.output_field)  # type: ignore
+        field_type = field_type_map.get(model_field_type, NotImplemented)
     # Every other Field possibility
     else:
         force_global_id = settings["MAP_AUTO_ID_AS_GLOBAL_ID"]

tests/fields/test_types.py

@@ -2,8 +2,9 @@
 import decimal
 import enum
 import uuid
-from typing import Dict, List, Tuple, Union, cast
+from typing import Any, Dict, List, Optional, Tuple, Union, cast
 
+import django
 import pytest
 import strawberry
 from django.conf import settings
@@ -21,6 +22,12 @@
 
 import strawberry_django
 from strawberry_django.fields.field import StrawberryDjangoField
+from strawberry_django.type import _process_type  # noqa: PLC2701
+
+if django.VERSION >= (5, 0):
+    from django.db.models import GeneratedField  # type: ignore
+else:
+    GeneratedField = None
 
 
 class FieldTypesModel(models.Model):
@@ -46,6 +53,24 @@ class FieldTypesModel(models.Model):
     url = models.URLField()
     uuid = models.UUIDField()
     json = models.JSONField()
+    generated_decimal = (
+        GeneratedField(
+            expression=models.F("decimal") * 2,
+            db_persist=True,
+            output_field=models.DecimalField(),
+        )
+        if GeneratedField is not None
+        else None
+    )
+    generated_nullable_decimal = (
+        GeneratedField(
+            expression=models.F("decimal") * 2,
+            db_persist=True,
+            output_field=models.DecimalField(null=True, blank=True),
+        )
+        if GeneratedField is not None
+        else None
+    )
     foreign_key = models.ForeignKey(
         "FieldTypesModel",
         blank=True,
@@ -91,8 +116,7 @@ class Type:
         uuid: auto
         json: auto
 
-    object_definition = get_object_definition(Type, strict=True)
-    assert [(f.name, f.type) for f in object_definition.fields] == [
+    expected_types: list[tuple[str, Any]] = [
         ("id", strawberry.ID),
         ("boolean", bool),
         ("char", str),
@@ -118,6 +142,17 @@ class Type:
         ("json", JSON),
     ]
 
+    if django.VERSION >= (5, 0):
+        Type.__annotations__["generated_decimal"] = auto
+        expected_types.append(("generated_decimal", decimal.Decimal))
+
+        Type.__annotations__["generated_nullable_decimal"] = auto
+        expected_types.append(("generated_nullable_decimal", Optional[decimal.Decimal]))
+
+    type_to_test = _process_type(Type, model=FieldTypesModel)
+    object_definition = get_object_definition(type_to_test, strict=True)
+    assert [(f.name, f.type) for f in object_definition.fields] == expected_types
+
 
 def test_subset_of_fields():
     @strawberry_django.type(FieldTypesModel)