serializers.JSONField() openapi definition should include additionalProperties: true

[johnnymetz]

Background

Looks like my_field = serializers.JSONField() currently generates the following openapi spec:

my_field:
  type: object

It should generate the following spec (or at least provide an option to generate it):

my_field:
  type: object
  additionalProperties: true

The reason being that the latter is considered a "free-form" object, which can have any key-value pairs (see here).

The former is generally considered an empty object, see here: openapi-ts/openapi-typescript#1004 (comment)

Implementation Notes

• Looks like this can be implemented in AutoSchema.map_field() here:

  django-rest-framework/rest_framework/schemas/openapi.py

  Line 368 in 041b88f

  def map_field(self, field):

Probably just need to include the following snippet inside that method:

if isinstance(field, serializers.JSONField):
    return {
        'type': 'object',
        'additionalProperties': 'true'
    }

[auvipy]

you can send an improvement request or you can also try drf-spectacular as default schema generator