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.

[roniemartinez]

We are getting the same error using GeneratedField.

TypeError: DecimalField.__init__() missing 2 required positional arguments: 'max_digits' and 'decimal_places'

[aan1173]

I meet the similar error using 'GeneratedField' with 'DecimalField' TypeError: DecimalField.__init__() missing 2 required positional arguments: 'max_digits' and 'decimal_places'

class Product(models.Model):
    name = models.CharField(max_length=255)
    price = models.DecimalField(max_digits=5, decimal_places=2)
    number = models.IntegerField()
    description = models.TextField()
    release_date = models.DateField()
    manufacturer = models.ForeignKey(Manufacturer, on_delete=models.CASCADE)
    ERROR_in_swaggerUI = models.GeneratedField(
        expression=F("price") * F("number"),
        output_field=models.DecimalField(max_digits=15, decimal_places=2),
        db_persist=True,
    )
    OK_in_swaggerUI = models.GeneratedField(
        expression=F("price") * F("number"),
        output_field=models.FloatField(),
        db_persist=True,
    )

Everything is ok if we comment out the "ERROR_in_swaggerUI" above

[tfranzel]

Sry this kinda fell of the waggon. I did indeed tried to parse this field for some time, but I turned out to be weirdly complicated.

I will make another attempt at this, but if it does not work out, at least we should fall back to a str default and not raise any exceptions until we can figure out a better solution.