Extend ModelSerializer autogenerated fields

Describe the bug

It is not possible to extend fields which were autogenerated by a ModelSerializer. Defining a custom serializerfield and extending it results in loosing the Info provided by the model field.

To Reproduce

Suppose the following model:

class Word(SolidBaseProfile):
    name = models.CharField(max_length=200, verbose_name=_("Titel"))

    graphic = models.TextField(
        max_length=500,
        null=True,
        blank=True,
        verbose_name=_("Graphie"),
    )

Furthermore let’s say we introduce a new “type” of string called “mdstring” to let our forntend know, that it has to render the contents as markdown formatted text.

If you define the following field + serializer

@extend_schema_field({"type": "mdstring"})
class MDStringField(serializers.CharField):
    pass

class WordSerializer(serializers.ModelSerializer):
    graphic = MDStringField()

    class Meta:
        model = Word
        fields = "__all__"

The resulting Schema becomes:

    Word:
      type: object
      properties:
        id:
          type: integer
          readOnly: true
        graphic:
          type: mdstring
        name:
          type: string
          title: Titel
          maxLength: 200

Expected behavior

Since i’m not sure if this is a pure drf-spectacular Problem i’m just stating what i would like to achive.

The schema i would like to see is:

    Word:
      type: object
      properties:
        id:
          type: integer
          readOnly: true
        graphic:
          type: mdstring
          nullable: true
          title: Graphie
          maxLength: 500
        name:
          type: string
          title: Titel
          maxLength: 200

[chgad]

I tested this and it works. You just have to set it up once I use this kind of thing myself for yaml string and even added validation to the fields.

Ooooooh that’s how the FieldExtensions ar supposed to work! Well that explains a lot now. And if I think about it: It’s somewhat similar to my suggestion above.

Thank you very much for your time and effort.

Consider this issue closed.

[tfranzel]

awesome!