[Bug] @validate decorator doesn't work for Class-Based Views #2483

[adamcohenhillel]

Describe the bug
While using the @validate decorator on a class-based view, I get the following exception:

[...]python/site-packages/sanic_ext/extras/validation/decorator.py", line 39, in decorated_function
    data=request.json,
AttributeError: 'SomeResource' object has no attribute 'json'

And this is how my Class Based view look like:

class SomeResource(HTTPMethodView):
    @validate(json=ResourceSchema)
    async def post(self, request):
        pass

Additional Notes
Diving quickly into the code of the decorator, it seems like we are not handling the class case of the views, where the first argument of the method is the class instance and not the request instance (like in the function-based view):

async def decorated_function(request: Request, *args, **kwargs):

I think a solution for that can be to use the kwargs rather than the position, but I am not too familiar with the codebase just yet, so there might be a more suitable solution for this repo.

[ahopkins]

Thanks, for jumping on this.