Unify behavior between asgi and wsgi

[CaselIT]

Currently the implementation of the response class for the wsgi and the asgi differ when handling the data property. Namely the asgi version does not override data with the media value, while the wsgi version overrides the data with the media serialization data.

In the code on master there are currently these todos

falcon/falcon/response.py

Lines 192 to 195 in c3e9187

	# TODO(kgriffs): Remove the side-effect that accessing this
	# property causes (do something similar to what we did on the
	# ASGI side). This will be a breaking change, so caution is
	# advised.

falcon/falcon/response.py

Lines 192 to 195 in c3e9187

	# TODO(kgriffs): Remove the side-effect that accessing this
	# property causes (do something similar to what we did on the
	# ASGI side). This will be a breaking change, so caution is
	# advised.

Should the wsgi response class behave like the asgi, and use the method render_body to get the body in the response?

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[CaselIT]

@vytas7 on gitter pointed out that there are also other differences between wsgi and asgi. Like the Request.get_media and the current draft of the async multipart media handler

This is mainly because an async property is odd, and may trick people that are not used to this.

To try and have an api as uniform as possible between asgi and wsgi, maybe an heuristic could be:

• takes constant time to execute regardless of the request? a property is probably fine in both cases (not async in asgi)
• depends on the request/resposne? a function is probably better, and the asgi would be async

[vytas7]

Anything doing I/O is probably better off as a method.
Async makes it crystal clear by requiring you to await things.

However, even if we adopt this thinking, we'll have to provide WSGI property compatibility aliases for a long time. Serious interface stability is among the main selling points of Falcon, after all.

[CaselIT]

If they are just getters, the alias would be just media = property(get_media)

Maybe the path could be. Alias in v3 (maybe deprecated just in the comments), deprecate in v4, remove v5?

For asgi and multipart, since they are new, the alias would not be there?

[kgriffs]

Maybe the path could be. Alias in v3 (maybe deprecated just in the comments), deprecate in v4, remove v5?

I'd say just alias in v3 but do not deprecated until v4.

For asgi and multipart, since they are new, the alias would not be there?

For ASGI we are trying to make it as similar as possible to WSGI (minus stuff that is deprecated in WSGI for v3), so I think it would still be a good idea to, for example, add a req.media property alias.

[CaselIT]

I can try working on it. I'll start by unifying the request and response classes

[vytas7]

@CaselIT I think you should coordinate this with @kgriffs as we've just merged the PR for ASGI reintroducing the async asgi.Request.media property.
It might be worth getting some feedback from the community first, i.e., whether people want to move away from properties at all wrt WSGI Falcon. On WSGI Falcon it's convenient to do, for instance, just req.media.

One thing that is IMHO clearly worth unifying, is render_body(). I'm not very opinionated on property vs method otherwise.

[CaselIT]

Yes, that was the plan for now I think. Have both, at least in the wsgi version.
Then for v4 it can be decided if only one solution should be kept or not, and apply the appropriate deprecations.

[kgriffs]

Let's start with a PR and breaking change notes in docstrings and towncrier news for updating WSGI per render_body().

Can you enumerate/add a checklist for any other changes you were considering?

[CaselIT]

Here is what I've found:

• Request: bounded_stream vs stream. Not sure any change can be made here since in wsgi are two different values, while asgi are aliased
• BodyPart: I guess all properties should be alias of methods get_X

It's probably not exhaustive