Can't extract type from GeneratedField

[ckarli]

Describe the bug
Types can't be extracted from newly added GeneratedField. Field must be added explicitly to the serializer with the correct type as defined in the "output_field". Otherwise it gives the error below.

backend-1 | Traceback (most recent call last):
backend-1 | File "/usr/local/lib/python3.12/site-packages/django/contrib/staticfiles/handlers.py", line 80, in call
backend-1 | return self.application(environ, start_response)
backend-1 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
backend-1 | File "/usr/local/lib/python3.12/site-packages/sentry_sdk/integrations/django/init.py", line 165, in sentry_patched_wsgi_handler
backend-1 | return SentryWsgiMiddleware(bound_old_app, use_x_forwarded_for)(
backend-1 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
backend-1 | File "/usr/local/lib/python3.12/site-packages/sentry_sdk/integrations/wsgi.py", line 115, in call
backend-1 | reraise(*_capture_exception(hub))
backend-1 | File "/usr/local/lib/python3.12/site-packages/sentry_sdk/_compat.py", line 127, in reraise
backend-1 | raise value
backend-1 | File "/usr/local/lib/python3.12/site-packages/sentry_sdk/integrations/wsgi.py", line 108, in call
backend-1 | rv = self.app(
backend-1 | ^^^^^^^^^
backend-1 | File "/usr/local/lib/python3.12/site-packages/django/core/handlers/wsgi.py", line 124, in call
backend-1 | response = self.get_response(request)
backend-1 | ^^^^^^^^^^^^^^^^^^^^^^^^^^
backend-1 | File "/usr/local/lib/python3.12/site-packages/sentry_sdk/integrations/django/init.py", line 460, in sentry_patched_get_response
backend-1 | rv = old_get_response(self, request)
backend-1 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
backend-1 | File "/usr/local/lib/python3.12/site-packages/django/core/handlers/base.py", line 140, in get_response
backend-1 | response = self._middleware_chain(request)
backend-1 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
backend-1 | File "/usr/local/lib/python3.12/site-packages/django/core/handlers/exception.py", line 57, in inner
backend-1 | response = response_for_exception(request, exc)
backend-1 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
backend-1 | File "/usr/local/lib/python3.12/site-packages/django/core/handlers/exception.py", line 140, in response_for_exception
backend-1 | response = handle_uncaught_exception(
backend-1 | ^^^^^^^^^^^^^^^^^^^^^^^^^^
backend-1 | File "/usr/local/lib/python3.12/site-packages/django/core/handlers/exception.py", line 181, in handle_uncaught_exception
backend-1 | return debug.technical_500_response(request, *exc_info)
backend-1 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
backend-1 | File "/usr/local/lib/python3.12/site-packages/django_extensions/management/technical_response.py", line 40, in null_technical_500_response
backend-1 | raise exc_value.with_traceback(tb)
backend-1 | File "/usr/local/lib/python3.12/site-packages/django/core/handlers/exception.py", line 55, in inner
backend-1 | response = get_response(request)
backend-1 | ^^^^^^^^^^^^^^^^^^^^^
backend-1 | File "/usr/local/lib/python3.12/site-packages/django/core/handlers/base.py", line 197, in _get_response
backend-1 | response = wrapped_callback(request, *callback_args, **callback_kwargs)
backend-1 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
backend-1 | File "/usr/local/lib/python3.12/site-packages/sentry_sdk/integrations/django/views.py", line 84, in sentry_wrapped_callback
backend-1 | return callback(request, *args, **kwargs)
backend-1 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
backend-1 | File "/usr/local/lib/python3.12/site-packages/django/views/decorators/csrf.py", line 65, in _view_wrapper
backend-1 | return view_func(request, *args, **kwargs)
backend-1 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
backend-1 | File "/usr/local/lib/python3.12/site-packages/django/views/generic/base.py", line 104, in view
backend-1 | return self.dispatch(request, *args, **kwargs)
backend-1 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
backend-1 | File "/usr/local/lib/python3.12/site-packages/rest_framework/views.py", line 509, in dispatch
backend-1 | response = self.handle_exception(exc)
backend-1 | ^^^^^^^^^^^^^^^^^^^^^^^^^^
backend-1 | File "/usr/local/lib/python3.12/site-packages/rest_framework/views.py", line 469, in handle_exception
backend-1 | self.raise_uncaught_exception(exc)
backend-1 | File "/usr/local/lib/python3.12/site-packages/rest_framework/views.py", line 480, in raise_uncaught_exception
backend-1 | raise exc
backend-1 | File "/usr/local/lib/python3.12/site-packages/rest_framework/views.py", line 506, in dispatch
backend-1 | response = handler(request, *args, **kwargs)
backend-1 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
backend-1 | File "/usr/local/lib/python3.12/site-packages/drf_spectacular/views.py", line 84, in get
backend-1 | return self._get_schema_response(request)
backend-1 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
backend-1 | File "/usr/local/lib/python3.12/site-packages/drf_spectacular/views.py", line 92, in _get_schema_response
backend-1 | data=generator.get_schema(request=request, public=self.serve_public),
backend-1 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
backend-1 | File "/usr/local/lib/python3.12/site-packages/drf_spectacular/generators.py", line 281, in get_schema
backend-1 | paths=self.parse(request, public),
backend-1 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
backend-1 | File "/usr/local/lib/python3.12/site-packages/drf_spectacular/generators.py", line 252, in parse
backend-1 | operation = view.schema.get_operation(
backend-1 | ^^^^^^^^^^^^^^^^^^^^^^^^^^
backend-1 | File "/usr/local/lib/python3.12/site-packages/drf_spectacular/openapi.py", line 99, in get_operation
backend-1 | request_body = self._get_request_body()
backend-1 | ^^^^^^^^^^^^^^^^^^^^^^^^
backend-1 | File "/usr/local/lib/python3.12/site-packages/drf_spectacular/openapi.py", line 1295, in _get_request_body
backend-1 | schema, partial_request_body_required = self._get_request_for_media_type(serializer, direction)
backend-1 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
backend-1 | File "/usr/local/lib/python3.12/site-packages/drf_spectacular/openapi.py", line 1327, in _get_request_for_media_type
backend-1 | component = self.resolve_serializer(serializer, direction)
backend-1 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
backend-1 | File "/usr/local/lib/python3.12/site-packages/drf_spectacular/openapi.py", line 1605, in resolve_serializer
backend-1 | component.schema = self._map_serializer(serializer, direction, bypass_extensions)
backend-1 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
backend-1 | File "/usr/local/lib/python3.12/site-packages/drf_spectacular/openapi.py", line 927, in _map_serializer
backend-1 | schema = self._map_basic_serializer(serializer, direction)
backend-1 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
backend-1 | File "/usr/local/lib/python3.12/site-packages/drf_spectacular/openapi.py", line 1026, in _map_basic_serializer
backend-1 | schema = self._map_serializer_field(field, direction)
backend-1 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
backend-1 | File "/usr/local/lib/python3.12/site-packages/drf_spectacular/openapi.py", line 904, in _map_serializer_field
backend-1 | schema = self._map_model_field(field.model_field, direction)
backend-1 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
backend-1 | File "/usr/local/lib/python3.12/site-packages/drf_spectacular/openapi.py", line 612, in _map_model_field
backend-1 | return self._map_serializer_field(field_cls(), direction)
backend-1 | ^^^^^^^^^^^^^^^^^^^^^^^
backend-1 | TypeError: DecimalField.init() missing 2 required positional arguments: 'max_digits' and 'decimal_places'

To Reproduce

class Invoice(models.Model):
    #...omitting amount_from and xrate_from fields
    amount= models.GeneratedField(
        expression=F("amount_from") * F("xrate_from"),
        output_field=models.DecimalField(max_digits=19, decimal_places=4),
        db_persist=True,
    )

Use GeneratedField in a model, and use this model in a ModelSerializer's fields parameter.

class InvoiceSerializer(serializers.ModelSerializer):

class Meta:
    model = Invoice
    fields = ("amount",)

Expected behavior
Field type must be inferred from output_field

[tfranzel]

Interesting. I was not aware of that new field type. Will have to investigate on how to handle the field. Seems like output_field is pretty much the only option for extraction.