"UUID is not JSON serializable" when generating a schema for a choice field with UUID options.

[phb-teleclinic]

Describe the bug
drf-spectacular crashes when generating a schema for a choice field with UUID options.

To Reproduce

Using drf-spectacular 0.26.4.

Create and API with the following serializer:

import uuid
from rest_framework import serializers

class TestSerializer(serializers.Serializer):
    foo_field = serializers.ChoiceField(
        allow_null=True,
        choices=[
            (uuid.UUID('44ec224e-0d22-48f0-07e2-2fc996160e25'), 'foo'),
            (uuid.UUID('cffceb17-8c0z-434e-9aba-de5f5126d558'), 'bar')
        ]
    )

generating the schema for the API triggers:

    schema = generator.get_schema(request=None, public=True)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    result = hook(result=result, generator=self, request=request, public=public)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/test-venv/lib/python3.11/site-packages/drf_spectacular/hooks.py", line 116, in postprocess_schema_enums
    prop_hash = list_hash(prop_schema['enum'])
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/test-venv/lib/python3.11/site-packages/drf_spectacular/plumbing.py", line 837, in list_hash
    return hashlib.sha256(json.dumps(list(lst), sort_keys=True).encode()).hexdigest()
                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    **kw).encode(obj)
          ^^^^^^^^^^^
    chunks = self.iterencode(o, _one_shot=True)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    return _iterencode(o, 0)
           ^^^^^^^^^^^^^^^^^
    raise TypeError(f'Object of type {o.__class__.__name__} '
TypeError: Object of type UUID is not JSON serializable

Expected behavior
Expected the schema generation to succeed.

Possible fix
Change list_hash to use a JSON encoder that supports UUIDs like DjangoJSONEncoder.

[tfranzel]

Hi @phb-teleclinic,

interesing usage of the choices parameter. I think people usually just drop in the UUID string in that case, but your solution is indeed a bit more robust. I think it is a good idea to employ the same serialization as the framework does.

[tfranzel]

Excellent! Thanks @phb-teleclinic for the PR