[Feature] - Support Pydantic 2 and remove support for Pydantic V1

[cgearing]

This PR updates Flask-Pydantic-Spec to only support Pydantic V2. After this PR is merged, only Pydantic V2 will be supported by Flask-Pydantic-Spec.

As part of this upgrade, we have decided to fully target OpenAPI 3.1 as the output of the library. As such, there are a few changes to keep in mind.

1. It's not valid in OpenAPI 3.1 for a path to not return some kind of response, and if it does, it should be a successful response. As such, Flask-Pydantic-Spec will now raise an error if there is no response defined for a view.
2. [ and ] is not allowed in the name of the schema, so we will replace these character with _.
3. Expands testing to also run against Python 3.12
4. Updates Flake8 dependency to latest

[FrankTub]

This would be really awesome! Running into the issue that I can't use this package without downgrading Pydantic to <2

[FrankTub]

@robyoung , is it realistic to expect this to be merged any time soon and result in a new version?

[robyoung]

Sorry, this totally dropped off my radar.

[FrankTub]

@robyoung , any idea when this will be available on pypi?

[FrankTub]

@robyoung , what is needed for this PR to be merged and deployed to pypi?

[FrankTub]

I tried to run this locally with a forked repo of this change but this results in an error:

[FrankTub]

Reverting it to self.OPENAPI_VERSION: str = "3.0.3" resolves the issue for me.

[eyalruby]

Please merge

[DonaldNgai]

@cgearing Could you please merge this?

@FrankTub @robyoung , anyway to push this if @cgearing doesn't respond?

[kedvall]

Hello, when trying to test this branch I found a couple of issues.

1. When sending a request that causes a validation error, Flask crashes.

Steps to reproduce...

Add the following dummy route to examples/flask_demo.py:

@app.route('/api/test-error', methods=['POST'])
@api.validate(body=Data, resp=Response('HTTP_200'))
def test_error():
    return "PASS"

Call the route without passing a Data object in the request body:
http POST localhost:8000/api/test-error

Resulting exception:

 * Serving Flask app 'flask_demo'
 * Debug mode: off
WARNING: This is a development server. Do not use it in a production deployment. Use a production WSGI server instead.
 * Running on http://127.0.0.1:8000
Press CTRL+C to quit
[2025-02-18 17:36:50,449] ERROR in app: Exception on /api/test-error [POST]
Traceback (most recent call last):
  File "/Users/kedvall/dev/flask-pydantic-spec/.venv/lib/python3.10/site-packages/flask/app.py", line 1511, in wsgi_app
    response = self.full_dispatch_request()
  File "/Users/kedvall/dev/flask-pydantic-spec/.venv/lib/python3.10/site-packages/flask/app.py", line 919, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/Users/kedvall/dev/flask-pydantic-spec/.venv/lib/python3.10/site-packages/flask/app.py", line 917, in full_dispatch_request
    rv = self.dispatch_request()
  File "/Users/kedvall/dev/flask-pydantic-spec/.venv/lib/python3.10/site-packages/flask/app.py", line 902, in dispatch_request
    return self.ensure_sync(self.view_functions[rule.endpoint])(**view_args)  # type: ignore[no-any-return]
  File "/Users/kedvall/dev/flask-pydantic-spec/flask_pydantic_spec/spec.py", line 129, in sync_validate
    return self.backend.validate(
  File "/Users/kedvall/dev/flask-pydantic-spec/flask_pydantic_spec/flask_backend.py", line 200, in validate
    before(request, response, req_validation_error, None)
  File "/Users/kedvall/dev/flask-pydantic-spec/flask_pydantic_spec/utils.py", line 186, in default_before_handler
    "spectree_model": req_validation_error.model.__name__,
AttributeError: 'pydantic_core._pydantic_core.ValidationError' object has no attribute 'model'
127.0.0.1 - - [18/Feb/2025 17:36:50] "POST /api/test-error HTTP/1.1" 500 -

I think this can be fixed via changing .model to .__class__ in default_before_handler and default_after_handler. This should give ValidationError and fixes the exception:

def default_before_handler(
    req: Request, resp: Response, req_validation_error: Any, instance: BaseModel
) -> None:
    """
    default handler called before the endpoint function after the request validation

    :param req: request provided by the web framework
    :param resp: response generated by Flask_Pydantic_Spec that will be returned
        if the validation error is not None
    :param req_validation_error: request validation error
    :param instance: class instance if the endpoint function is a class method
    """
    if req_validation_error:
        logger.info(
            "Validation Error",
            extra={
                "spectree_model": req_validation_error.__class__.__name__,        # .model --> .__class__
                "spectree_validation": req_validation_error.errors(),
            },
        )


def default_after_handler(
    req: Request, resp: Response, resp_validation_error: Any, instance: BaseModel
) -> None:
    """
    default handler called after the response validation

    :param req: request provided by the web framework
    :param resp: response from the endpoint function (if there is no validation error)
        or response validation error
    :param resp_validation_error: response validation error
    :param instance: class instance if the endpoint function is a class method
    """
    if resp_validation_error:
        logger.info(
            "500 Response Validation Error",
            extra={
                "spectree_model": resp_validation_error.__class__.__name__,      # .model --> .__class__
                "spectree_validation": resp_validation_error.errors(),
            },
        )

2. The model config key schema_extra has been renamed to json_schema_extra and should be updated in examples/flask_demo.py:

class Data(BaseModel):
    uid: str
    limit: int = 5
    vip: bool

    class Config:
        json_schema_extra = {                            # schema_extra --> json_schema_extra
            'example': {
                'uid': 'very_important_user',
                'limit': 10,
                'vip': True,
            }
        }