RELEASE

This release adds configurable exception handlers that map Python exceptions to typed GraphQL union results.

Most applications do not need to adopt this directly. It is primarily useful for integrations and framework-level helpers: for example, catching validation exceptions from a library such as Pydantic and exposing them as an explicit GraphQL error type, without requiring every resolver to catch and convert those exceptions manually.

Handlers are passed to strawberry.Schema (and strawberry.federation.Schema):

import strawberry
from strawberry.types.field import StrawberryField


class ValidationProblem(Exception):
    pass


@strawberry.type
class ValidationError:
    message: str


class ValidationErrorHandler(
    strawberry.ExceptionHandler[ValidationProblem, ValidationError]
):
    def handle(
        self,
        exception: ValidationProblem,
        *,
        field: StrawberryField,
        info: strawberry.Info,
    ) -> ValidationError:
        return ValidationError(message=str(exception))


schema = strawberry.Schema(
    query=Query,
    mutation=Mutation,
    exception_handlers=[ValidationErrorHandler()],
)

Handlers can alternatively declare exception_type and error_type class attributes instead of type parameters, which also covers types that are only known at runtime. Declaring both a type parameter and a conflicting attribute for the same slot raises an error at schema creation.

Strawberry only converts the exception when the field return type includes the handler's GraphQL error type. Other fields continue to raise normal GraphQL errors, so applications can opt in one field at a time. Exceptions raised by the resolver, during argument conversion, or by field extensions are all covered.

Exception handlers apply to query and mutation fields. Subscriptions are not covered: exceptions raised while establishing a subscription are not converted into union results.