[Bug] Dependency injection fails when multiple routes share the same name about sanic-ext

[ahopkins]

1. url_for is the only place the core project uses it. However, we've been moving towards pushing naming in Apps and Blueprints for several years now. In last LTS (for example) strict enforcement is enabled for app and blueprint naming. This is part of that shift.
2. It uses handler because that's fairly descriptive for what it is. AFAIK it does not use two similarly named functions in the same example. If it does we should fix that.
3. Yes, it works, which is why we have not broken that and do not have a current plan to. I'd like to strictly enforce, but there has not yet been a need to push that. Other python tools like flake8 will yell at you for this.
4. What Flask does is fairly irrelevant and would not sway my opinion in either direction.
5. There is not currently a unique naming requirement. I would like to enforce that, but we are several release cycles away from being able to do that.

With that all said, we probably should add the warning to 21.3 and aim for enforcement by the end of the year.

[ahopkins]

This is discouraged for sure. It probably should be a warning by the core project.

[xmcp]

I surveyed the Sanic docs for a while before posting this issue, and I wonder whether duplicate route names are really discouraged.

Here are some findings:

• The API doc for Sanic.route says that the name is an Optional[str] as a "user defined route name for url_for". It suggests that a unique name is optional and only needed by url_for.
• The Sanic user guide itself heavily uses handler as the function name, which is not unique.
• It actually works perfectly fine if handler names are not unique.

By comparison, Flask said in its API doc that endpoint names should not duplicate, and it raises AssertionError: View function mapping is overwriting an existing endpoint function: handler before server startup if the developer really violates this.

So if you are sure that handler names must be unique in Sanic, I would suggest a warning both in the user guide and in the Sanic code.