Move exception handling logic to Route

[adriangb]

Fixes #493, partially resolves #1692 (comment), resolves #1649 (comment)

By moving handling of exceptions to the Route level we can use the same Request/WebSocket object for the endpoint and exception handlers.

See #2020 for some more background

[Kludex]

I'm positive towards this PR. Is any other member that wants to check it? @encode/maintainers

[adriangb]

@tomchristie it would be great to get your eyes on this since no one has really changed this part of the codebase since you originally wrote it

[Kludex]

Are you strong about this code structure?

Do you mind if we maintain the exceptions.py and create a _<some_good_name_at_root_level>? I feel like importing wrap_app_handling_exceptions from middleware/exceptions is not very logic. 🤔

@encode/maintainers If someone is against this idea, or has any concerns regarding this, or want more context, anything... Please let us know. Otherwise, I'll get this merged end of next week.

[adriangb]

this does not solve the problem when someone wants to access request.body in other middleware. This issue is still there, isn't it? This solution (#1519) is more straightforward as fixes the issue everywhere.

#1692 also resolves it in a way that compliments this PR, and without breaking other things.

[adriangb]

Folks, it would be great to get some more input/review here.

[Kludex]

The last bits here:

What's our plan regarding the ExceptionMiddleware? Are we going to remove it at some point?

Also, should we update the documentation: https://www.starlette.io/exceptions/#errors-and-handled-exceptions ?

[Kludex]

Do you mind if we change the structure of the files around (I can change it)?

I'd prefer to not remove the file exceptions.py, and just create a top level _exception_handler.py.

[adriangb]

Sure go for it

[Kludex]

@adriangb I didn't change the documentation, but I think we should do something there for 1.0.

Also, I applied this commit: 3fb1118 (#2026). If you didn't like it, let me know, so I can revert it. 👍