Multiple Choice fields don't generate the proper schema

[SafaAlfulaij]

FilterSet

class ObjectsFilterSet(FilterSet):
    type = MultipleChoiceFilter(
        field_name='type',
        label='Type of object',
        choices=(
            ('A', 'A'),
            ('B', 'B'),
            ('C', 'C')
        ),
    )

Current result

      - name: type
        required: false
        in: query
        description: Type of object
        schema:
          type: string
          enum:
            - A
            - B
            - C

Expected result

      - name: type
        required: false
        in: query
        description: Type of object
        schema:
          type: array
          items:
            type: string
            enum:
            - A
            - B
            - C

Proposed solution

Fix https://github.com/carltongibson/django-filter/blob/master/django_filters/rest_framework/backends.py#L168:

            if field.extra and 'choices' in field.extra:
                parameter['schema']['enum'] = [c[0] for c in field.extra['choices']]

            if isinstance(field, (MultipleChoiceFilter, ModelMultipleChoiceFilter)):
                parameter['schema'] = {
                    'type': 'array',
                    'items': parameter['schema']
                }

[elonzh]

fixed in https://github.com/tfranzel/drf-spectacular/blob/0f3e8f134a3214271fabc2b81283123d7bdf6c48/drf_spectacular/contrib/django_filters.py#L130

[carltongibson]

Moving to #1432