Blueprints not handling errors on 21.9.0

[aericson]

Describe the bug
Error handler on the blueprint is no longer working with 21.9.0. Worked fine on 21.6.2

Code snippet
I've created a reproducible simplified version on the repo here: https://github.com/aericson/sanic-blueprint-error-demo
You should be able to see the error on the Github Action here: https://github.com/aericson/sanic-blueprint-error-demo/actions/runs/1295855511

server:

##### blueprint
bp = Blueprint(__name__)


@bp.exception(Exception)
async def oops(request, exception):
    return text("OOops")
####### server
 def init_app():
    app = Sanic("MyHelloWorldApp")

    @app.get("/")
    async def hello_world(request):
        raise Exception("this is an exception")

    app.blueprint(bp)

    return app

Expected behavior
Expected a request to / to respond with the return of the error handler. Returned 500 instead.

Environment (please complete the following information):

• OS: Any
• Version 21.9.0

[prryplatypus]

Your example is not supposed to work the way you intend it to. Blueprint exception handlers are only supposed to handle exceptions that happen within their own scope. In your example, you're attaching an error handler to the blueprint, but your route is being attached to the app instance directly, not the blueprint.

The fact that it used to work was an unintended side-effect/bug which was fixed here: #2246

[aericson]

Your example is not supposed to work the way you intend it to. Blueprint exception handlers are only supposed to handle exceptions that happen within their own scope. In your example, you're attaching an error handler to the blueprint, but your route is being attached to the app instance directly, not the blueprint.

The fact that it used to work was an unintended side-effect/bug which was fixed here: #2246

I see, thanks for the quick reply @prryplatypus!

We are currently just using blueprints for error handling. I guess our options would then be to either drop blueprints and attach handlers to the app or move the routing to the blueprints entirely.

A bit unfortunately but at least it's clear where our problem is at now. Thank you!