Generated schema is not compatible with jsonschema's referencing

[stefanofusai]

I've currently implemented schema validation of API responses in my tests using python-jsonschema's RefResolver. Everything works perfectly!

from typing import Any

import openapi_schema_validator
from drf_spectacular.settings import spectacular_settings
from jsonschema import RefResolver
from openapi_schema_validator import OAS31Validator


@cache
def _get_schema(
    api_version: str = "v4",  # See: https://drf-spectacular.readthedocs.io/en/latest/faq.html#i-get-an-empty-schema-or-endpoints-are-missing
) -> dict[str, Any]:
    generator_class = spectacular_settings.DEFAULT_GENERATOR_CLASS
    generator = generator_class(api_version=api_version)
    return generator.get_schema(request=None, public=True)


def validate_schema(
    instance: dict[str, Any],
    *,
	version: str,
    path: str,
    method: str,
    response: str,
    content: str = "application/json",
) -> None:
    schema = _get_schema(version)

    try:
        _methods = schema["paths"][path]

    except KeyError:  # pragma: no cover (should never happen)
        msg = f"Path {path} not found in schema"
        raise ValueError(msg) from None

    try:
        _responses = _methods[method]

    except KeyError:  # pragma: no cover (should never happen)
        msg = f"Method {method} not found in schema"
        raise ValueError(msg) from None

    try:
        _content = _responses["responses"][response]["content"]

    except KeyError:  # pragma: no cover (should never happen)
        msg = f"Response {response} not found in schema"
        raise ValueError(msg) from None

    try:
        _schema = _content[content]["schema"]

    except KeyError:  # pragma: no cover (should never happen)
        msg = f"Content {content} not found in schema"
        raise ValueError(msg) from None

    # TODO: migrate to referencing lib
    openapi_schema_validator.validate(
        instance=instance,
        schema=_schema,
        cls=OAS31Validator,
        resolver=RefResolver.from_schema(schema),
    )

I use it as such:

validate_schema(response.json(), version=version, path=reverse("foo:bar"), method="get", response="200")

As described here, I'm now looking to migrate to the referencing library with code that looks like this:

resource = Resource.from_contents(schema, default_specification=DRAFT202012)
registry = Registry().with_resource("", resource)
openapi_schema_validator.validate(instance, _schema, registry=registry)

But I'm getting the following error: jsonschema.exceptions._WrappedReferencingError: PointerToNowhere: '/components/schemas/Foo' does not exist within {'$ref': '#/components/schemas/Foo'}

After asking for help in python-openapi (here) and python-jsonschema (here) it seems to me like it may be an issue with the generated schema and it's structure (which is generated by drf-spectacular)

Unfortunately I'm not an expert on this topic, so could you point me in the right direction and figure out where the issue may be?
Thank you!