AttributeError: 'method' object has no attribute '__blueprintname__'

Describe the bug

I am trying to structure my code following best practices, keeping everything contained within a class to avoid any global objects. When I attempt to contain my blueprints within the class object, I get the error in the title.

Code snippet

Minimal reproduction of the issue:

from sanic import Blueprint, Sanic


class Router(Sanic):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, name="Example", **kwargs)

        self._add_routes()

    def _add_routes(self):
        v1 = Blueprint("v1", version=1)
        v1.add_route(self._handle_v1_foo, "/foo")
        self.blueprint(v1)

        v2 = Blueprint("v2", version=2)
        v2.add_route(self._handle_v2_foo, "/foo")
        self.blueprint(v2)

    def _handle_v1_foo(self, request):
        pass

    def _handle_v2_foo(self, request):
        pass


app = Router()

Expected behavior

No error.

Actual behavior

Traceback (most recent call last):
  File "/private/tmp/tmp.ZKa5SvCjpA/main.py", line 26, in <module>
    app = Router()
  File "/private/tmp/tmp.ZKa5SvCjpA/main.py", line 8, in __init__
    self._add_routes()
  File "/private/tmp/tmp.ZKa5SvCjpA/main.py", line 13, in _add_routes
    self.blueprint(v1)
  File "/tmp/virtualenv/lib/python3.10/site-packages/sanic/app.py", line 527, in blueprint
    blueprint.register(self, options)
  File "/tmp/virtualenv/lib/python3.10/site-packages/sanic/blueprints.py", line 309, in register
    future.handler.__blueprintname__ = self.name
AttributeError: 'method' object has no attribute '__blueprintname__'

[ahopkins]

As for the question… I would not call that a bug. You are using Sanic and Blueprints in a way that was not anticipated. Unfortunately instance methods (TMK) cannot have properties assigned to them the way that functions can. This is why you see that message. Albeit it is somewhat of a “hack” to assign properties to a function, it is part of the under-the-hood magic that enables proper naming of handlers. So it might be possible to allow for instance methods to be used like this, but it would require some changes.

[ahopkins]

Actually… TBH, the more I look at it, I think this is deprecated code anyway. We probably can remove that assignment completely since it is no longer in use or needed.