Returning an Enum from a SerializerMethod

[johnthagen]

Is it possible to express this:

class Item(Model):
    name = TextField()

@unique
class Color(Enum):
    Red = "red"
    Green = "green"
    Blue = "blue"


class ItemSerializer(ModelSerializer):
    color = SerializerMethodField()

    def get_color(self, instance) -> Color:
        return Color.Red.value

    class Meta:
        model = Item
        fields = "__all__"

We've been able to use Enums directly within Models, using https://github.com/akx/django-enumfields2 and that translates properly into an OpenAPI enum.

Is there a way to expose similar functionality through a SerializerMethod in a way drf-spectacular can process?

[johnthagen]

Interesting, this does seem to somewhat work, even though from looking at the code and they type hints on @extend_schema_field, I didn't see Enum so I was expecting this to not work?

_KnownPythonTypes = typing.Type[typing.Union[
    str, float, bool, bytes, int, dict, UUID, Decimal, datetime, date, time,
    timedelta, IPv4Address, IPv6Address,
]]

I guess I'd like to check that this is intended behavior 😄 .

Edit: This only partially seems to work.

[johnthagen]

So this seems to generate:

    Item:
      type: object
      properties:
        id:
          type: integer
          readOnly: true
        color:
          allOf:
          - $ref: '#/components/schemas/ColorEnum'
          readOnly: true
        name:
          type: string
      required:
      - color
      - id
      - name

... 

    ColorEnum:
      enum:
      - red
      - green
      - blue

But something is not correct because the Swagger UI shows:

And "ENUM_NAME_OVERRIDES" does not seem to work within drf-spectacular.

[johnthagen]

Switching to @extend_schema_field seems to produce the same result.

    @extend_schema_field(Color)
    def get_color(self, instance) -> Any:
        return Color.Red.value

[johnthagen]

I think what's causing the error is the

allOf:

line. My other EnumFields that work properly don't have that wrapping the $ref in the generated OpenAPI spec.

[johnthagen]

@tfranzel If there is a proper way to do this, I'm also happy to add a FAQ entry about it. 😃

[johnthagen]

Okay, not sure why I didn't think of this at first, but using an EnumField does make this work:

from enumfields.drf import EnumField

class Item(Model):
    name = TextField()

@unique
class Color(Enum):
    Red = "red"
    Green = "green"
    Blue = "blue"


class ItemSerializer(ModelSerializer):
    color = SerializerMethodField()

    @extend_schema_field(EnumField(Color))
    def get_color(self, instance) -> str:
        return Color.Red.value

    class Meta:
        model = Item
        fields = "__all__"

If this is indeed the proper way to do this, I'm happy to make an FAQ. Also, I could potentially see someone who doesn't use https://github.com/akx/django-enumfields2 wanting to export a simple Enum from a SerializerMethodField, so perhaps it's still worth a more generic solution within drf-spectacular?

Maybe natively supporting the StrEnum as one of the _KnownPythonTypes?