views: apply decorators once

[ppanero]

The correct use case would be:

• The method/view gets decorated once
• The decorator is called each time the function is invoked

The current behaviour:

• The method/view is decorated each time a function (get, post, etc.) is invoked. This happens because it is being decorated in the dispatch_request.

The ideal would be to decorate each method once, to avoid having the same chain of decorators in every module (e.g. content negotiation happens always, request loading also...)

EDIT
Goal of this issue is to refactor BaseView to use decorators to hold the common decorators. This will:

• decorate in one place the common decorators
• decorate once when as_view is called

EDIT
As per comment below, we can't use decorators. The remaining issue is "decorating once". IMHO this is a nice to have, but not necessary now: the performance cost of this should be felt before. I suggest we delay this using my release management powers ⚡ 😉

[fenekku]

@ppanero I think this is solved. We decorate in one place (the BaseView) with decorators that apply to all Resource methods and more spericifc method-related decorators can be added on each method separately.

Did you have something else in mind?

[ppanero]

@fenekku The issue still applies, the main problem is that the decoration happens inside the dispatch_request. Which means that we are decorating on each request rather than once (at start time of the web app).

However, if the function invokation is moved to the __init__ the decorator is not applied to each method but to each class, and therefore not work.

So it is half done:

• ✅ Decorate only in one place
• ❌ Decorate at start time

[fenekku]

Ok, then we should use the decorators class variable from https://github.com/pallets/flask/blob/024f0d384cf5bb65c76ac59f8ddce464b2dc2ca1/src/flask/views.py#L56 . Will amend the issue to this.

[ppanero]

@fenekku when using that variable is the second point I was mentioning. Decorators are applied per class, and then not used in every function (get, post, etc). This would need some more research on the inner guts of flask/werkzeug I guess.

[fenekku]

Decorators are applied per class, and then not used in every function (get, post, etc).

I don't think I understand something here... With View's decorators the decorators are applied per class and used for get, post, ... When are they not used?

If the issue is about decorators only for some methods and not others, then that is already possible by putting a decorator on some methods and not others. In some cases, we could give extra support such as the 2nd option here: #59 .

[ppanero]

Theoretically what you say is right. However, when Alex and I tested it, this:

I don't think I understand something here... With View's decorators the decorators are applied per class and used for get, post, ... When are they not used?

Did not work. That is why I say it requires more research. Maybe we did something wrong, or maybe it is not working as intended.

[fenekku]

Strange, 🤔 I will check it out this week.

[fenekku]

This is what is preventing us from using the built-in decorators:

https://github.com/pallets/flask/blob/master/src/flask/app.py#L1852

return self.view_functions[rule.endpoint](**req.view_args)

because self is not passed in for MethodView decorators and we need it, we will do without it.