Use Strawberry exception handlers for Django errors

RELEASE.md

@@ -0,0 +1,9 @@
+---
+release type: minor
+---
+
+Add `DjangoExceptionHandler`, a schema-level Strawberry exception handler for
+converting Django `ValidationError`, `PermissionDenied`, and `ObjectDoesNotExist`
+exceptions into `OperationInfo` results. Combined with `handle_django_errors=True`,
+it also handles exceptions raised during input conversion or by sync and async field
+extensions.

docs/guide/error-handling.md

@@ -187,6 +187,34 @@ def some_mutation(self, data: str) -> Result:
     pass
 ```
 
+## Handling Errors Outside the Resolver
+
+`handle_django_errors=True` handles exceptions raised by the mutation resolver and
+adds `OperationInfo` to its return union. To handle the same Django exceptions from
+the rest of Strawberry's field execution pipeline, register
+`DjangoExceptionHandler` on the schema:
+
+```python title="schema.py"
+import strawberry
+import strawberry_django
+
+from .mutations import Mutation
+from .queries import Query
+
+
+schema = strawberry.Schema(
+    query=Query,
+    mutation=Mutation,
+    exception_handlers=[strawberry_django.DjangoExceptionHandler()],
+)
+```
+
+The schema-level handler also converts supported exceptions raised while building
+input objects or running field extensions, including async extensions. It is only
+selected for fields whose return union contains `OperationInfo`, so unrelated fields
+continue to return normal GraphQL errors. Using `handle_django_errors=True` adds that
+union member automatically.
+
 ## Custom Error Handling
 
 ### Custom Exception Classes

pyproject.toml

@@ -29,7 +29,7 @@ classifiers = [
   "Framework :: Django :: 6.0",
 ]
 requires-python = ">=3.10,<4.0"
-dependencies = ["django>=5.2", "asgiref>=3.8", "strawberry-graphql>=0.310.1"]
+dependencies = ["django>=5.2", "asgiref>=3.8", "strawberry-graphql>=0.321.0"]
 
 [project.urls]
 homepage = "https://strawberry.rocks/docs/django"

strawberry_django/__init__.py

@@ -2,6 +2,7 @@
 from typing import TYPE_CHECKING, Any
 
 from . import auth, federation, filters, mutations, ordering, pagination, relay
+from .exception_handlers import DjangoExceptionHandler
 from .fields.field import connection, field, node, offset_paginated
 from .fields.filter_order import filter_field, order_field
 from .fields.filter_types import (
@@ -40,6 +41,7 @@
     "ComparisonFilterLookup",
     "DateFilterLookup",
     "DatetimeFilterLookup",
+    "DjangoExceptionHandler",
     "DjangoFileType",
     "DjangoImageType",
     "DjangoModelType",

strawberry_django/exception_handlers.py

@@ -0,0 +1,84 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING, TypeAlias
+
+import strawberry
+from django.core.exceptions import (
+    NON_FIELD_ERRORS,
+    ObjectDoesNotExist,
+    PermissionDenied,
+    ValidationError,
+)
+from strawberry.utils.str_converters import to_camel_case
+
+from strawberry_django.fields.types import OperationInfo, OperationMessage
+
+if TYPE_CHECKING:
+    from collections.abc import Iterator
+
+    from strawberry.types import Info
+    from strawberry.types.field import StrawberryField
+
+DjangoError: TypeAlias = ValidationError | PermissionDenied | ObjectDoesNotExist
+
+
+def _get_validation_error_message(error: ValidationError) -> str:
+    if not error.message:
+        return "Unknown error"
+
+    return error.message % error.params if error.params else error.message
+
+
+def _get_validation_errors(error: DjangoError) -> Iterator[OperationMessage]:
+    if isinstance(error, PermissionDenied):
+        kind = OperationMessage.Kind.PERMISSION
+    elif isinstance(error, ValidationError):
+        kind = OperationMessage.Kind.VALIDATION
+    else:
+        kind = OperationMessage.Kind.ERROR
+
+    if isinstance(error, ValidationError) and hasattr(error, "error_dict"):
+        for field, field_errors in (error.error_dict or {}).items():
+            for field_error in field_errors:
+                yield OperationMessage(
+                    kind=kind,
+                    field=(to_camel_case(field) if field != NON_FIELD_ERRORS else None),
+                    message=_get_validation_error_message(field_error),
+                    code=getattr(field_error, "code", None),
+                )
+    elif isinstance(error, ValidationError) and hasattr(error, "error_list"):
+        for list_error in error.error_list or []:
+            yield OperationMessage(
+                kind=kind,
+                message=_get_validation_error_message(list_error),
+                code=getattr(error, "code", None),
+            )
+    else:
+        message = getattr(error, "msg", None)
+        if message is None:
+            message = str(error)
+
+        yield OperationMessage(
+            kind=kind,
+            message=message,
+            code=getattr(error, "code", None),
+        )
+
+
+def _operation_info_from_exception(error: DjangoError) -> OperationInfo:
+    return OperationInfo(messages=list(_get_validation_errors(error)))
+
+
+class DjangoExceptionHandler(
+    strawberry.ExceptionHandler[DjangoError, OperationInfo],
+):
+    """Convert expected Django exceptions into ``OperationInfo`` results."""
+
+    def handle(
+        self,
+        exception: DjangoError,
+        *,
+        field: StrawberryField,
+        info: Info,
+    ) -> OperationInfo:
+        return _operation_info_from_exception(exception)

strawberry_django/mutations/fields.py

@@ -5,7 +5,6 @@
 
 import strawberry
 from django.core.exceptions import (
-    NON_FIELD_ERRORS,
     ObjectDoesNotExist,
     PermissionDenied,
     ValidationError,
@@ -17,11 +16,12 @@
 from strawberry.utils.str_converters import capitalize_first, to_camel_case
 
 from strawberry_django.arguments import argument
+from strawberry_django.exception_handlers import _operation_info_from_exception
 from strawberry_django.fields.field import (
     StrawberryDjangoFieldBase,
     StrawberryDjangoFieldFilters,
 )
-from strawberry_django.fields.types import OperationInfo, OperationMessage
+from strawberry_django.fields.types import OperationInfo
 from strawberry_django.optimizer import DjangoOptimizerExtension, optimize
 from strawberry_django.permissions import filter_with_perms, get_with_perms
 from strawberry_django.resolvers import django_resolver
@@ -49,62 +49,6 @@
 _T = TypeVar("_T", bound="models.Model | list[models.Model]")
 
 
-def _get_validaton_error_message(error: ValidationError):
-    if not error.message:
-        return "Unknown error"
-
-    return error.message % error.params if error.params else error.message
-
-
-def _get_validation_errors(error: Exception):
-    if isinstance(error, PermissionDenied):
-        kind = OperationMessage.Kind.PERMISSION
-    elif isinstance(error, ValidationError):
-        kind = OperationMessage.Kind.VALIDATION
-    elif isinstance(error, ObjectDoesNotExist):
-        kind = OperationMessage.Kind.ERROR
-    else:
-        kind = OperationMessage.Kind.ERROR
-
-    if isinstance(error, ValidationError) and hasattr(error, "error_dict"):
-        # convert field errors
-        for field, field_errors in (error.error_dict or {}).items():
-            for e in field_errors:
-                yield OperationMessage(
-                    kind=kind,
-                    field=to_camel_case(field) if field != NON_FIELD_ERRORS else None,
-                    message=_get_validaton_error_message(e),
-                    code=getattr(e, "code", None),
-                )
-    elif isinstance(error, ValidationError) and hasattr(error, "error_list"):
-        # convert non-field errors
-        for e in error.error_list or []:
-            yield OperationMessage(
-                kind=kind,
-                message=_get_validaton_error_message(e),
-                code=getattr(error, "code", None),
-            )
-    else:
-        msg = getattr(error, "msg", None)
-        if msg is None:
-            msg = str(error)
-
-        yield OperationMessage(
-            kind=kind,
-            message=msg,
-            code=getattr(error, "code", None),
-        )
-
-
-def _handle_exception(error: Exception):
-    if isinstance(error, (ValidationError, PermissionDenied, ObjectDoesNotExist)):
-        return OperationInfo(
-            messages=list(_get_validation_errors(error)),
-        )
-
-    raise error
-
-
 class DjangoMutationBase(StrawberryDjangoFieldBase):
     def __init__(
         self,
@@ -166,19 +110,18 @@ def get_result(
         if not self.handle_errors:
             return self.resolver(source, info, args, kwargs)
 
-        # TODO: Any other exception types that we should capture here?
         try:
             resolved = self.resolver(source, info, args, kwargs)
-        except Exception as e:  # noqa: BLE001
-            return _handle_exception(e)
+        except (ValidationError, PermissionDenied, ObjectDoesNotExist) as error:
+            return _operation_info_from_exception(error)
 
         if inspect.isawaitable(resolved):
 
             async def async_resolver():
                 try:
                     return await resolved
-                except Exception as e:  # noqa: BLE001
-                    return _handle_exception(e)
+                except (ValidationError, PermissionDenied, ObjectDoesNotExist) as error:
+                    return _operation_info_from_exception(error)
 
             return async_resolver()
 

tests/conftest.py

@@ -198,7 +198,7 @@ class Query:
         tags: list[types.Tag] = strawberry_django.field()
 
     if request.param == "optimizer_enabled":
-        extensions = [DjangoOptimizerExtension()]
+        extensions = [DjangoOptimizerExtension]
     elif request.param == "optimizer_disabled":
         extensions = []
     else:

tests/extensions/test_validation_cache.py

@@ -20,7 +20,7 @@ def hello(self) -> str:
         def ping(self) -> str:
             return "pong"
 
-    schema = strawberry.Schema(query=Query, extensions=[DjangoValidationCache()])
+    schema = strawberry.Schema(query=Query, extensions=[DjangoValidationCache])
 
     query = "query { hello }"
 

tests/federation/test_resolve_reference.py

@@ -191,7 +191,7 @@ def hello(self) -> str:
     schema = FederationSchema(
         query=Query,
         types=[FruitType],
-        extensions=[RecordingOptimizerExtension()],
+        extensions=[RecordingOptimizerExtension],
     )
 
     fruit = models.Fruit.objects.create(name="optimized-fruit")

tests/federation/test_schema.py

@@ -682,7 +682,7 @@ def hello(self) -> str:
     schema = FederationSchema(
         query=Query,
         types=[FruitType],
-        extensions=[DjangoOptimizerExtension()],
+        extensions=[DjangoOptimizerExtension],
     )
 
     fruit = models.Fruit.objects.create(name="optimized")
@@ -732,7 +732,7 @@ def hello(self) -> str:
     schema = FederationSchema(
         query=Query,
         types=[FruitType, ColorType],
-        extensions=[DjangoOptimizerExtension()],
+        extensions=[DjangoOptimizerExtension],
     )
 
     color = models.Color.objects.create(name="yellow")

tests/relay/test_cursor_pagination.py

@@ -92,7 +92,7 @@ def projects_with_resolver() -> list[ProjectType]:
         return cast("list[ProjectType]", Project.objects.all().order_by("-pk"))
 
 
-schema = strawberry.Schema(query=Query, extensions=[DjangoOptimizerExtension()])
+schema = strawberry.Schema(query=Query, extensions=[DjangoOptimizerExtension])
 
 
 @pytest.fixture
@@ -1447,7 +1447,7 @@ class FruitQuery:
         fruits: DjangoCursorConnection[FruitGQL] = strawberry_django.connection()
 
     fruit_schema = strawberry.Schema(
-        query=FruitQuery, extensions=[DjangoOptimizerExtension()]
+        query=FruitQuery, extensions=[DjangoOptimizerExtension]
     )
 
     ft1 = models.FruitType.objects.create(name="tropical")
@@ -1520,7 +1520,7 @@ class FruitQuery:
         fruits: DjangoCursorConnection[FruitGQL] = strawberry_django.connection()
 
     fruit_schema = strawberry.Schema(
-        query=FruitQuery, extensions=[DjangoOptimizerExtension()]
+        query=FruitQuery, extensions=[DjangoOptimizerExtension]
     )
 
     ft1 = models.FruitType.objects.create(name="tropical")

tests/test_custom_connection.py

@@ -147,7 +147,9 @@ class StandardQuery:
     standard_schema = strawberry.Schema(
         query=StandardQuery,
         extensions=[
-            DjangoOptimizerExtension(enable_only_optimization=enable_only_optimization)
+            lambda: DjangoOptimizerExtension(
+                enable_only_optimization=enable_only_optimization,
+            ),
         ],
     )
 
@@ -243,7 +245,9 @@ def test_fragment_with_custom_connection_no_n1(enable_only_optimization: bool):
     schema = strawberry.Schema(
         query=Query,
         extensions=[
-            DjangoOptimizerExtension(enable_only_optimization=enable_only_optimization)
+            lambda: DjangoOptimizerExtension(
+                enable_only_optimization=enable_only_optimization,
+            ),
         ],
     )