uvcorn duplicates ASGI root_path when started with --root-path

[amol-]

If --root-path is used, uvcorn will prefix every request path with it:

https://github.com/encode/uvicorn/blob/master/uvicorn/protocols/http/h11_impl.py#L199-L200

This breaks ASGI web frameworks routing capabilities as a request for /proxy/hello would become /proxy/proxy/hello and thus, even if web frameworks strip the root_path (for example like Starlette does: https://github.com/encode/starlette/blob/342410d250687ec6bba16c20e3d309ae34826802/starlette/_utils.py#L97-L98 ) they would be unable to process the routing correctly.

When --root-path=/proxy is used it should probably be set into the request "scope", but paths should not be prefixed with it to avoid duplicating the prefix.

[Kludex]

When --root-path=/proxy is used it should probably be set into the request "scope" [...]

Where?

[amol-]

Sorry if I wasn't clear. The root_path is already correctly set in the "scope" (at https://github.com/encode/uvicorn/blob/master/uvicorn/protocols/http/h11_impl.py#L212 )

But it's also prefixed to the request path itself ( https://github.com/encode/uvicorn/blob/master/uvicorn/protocols/http/h11_impl.py#L199-L200 )

This causes an unexpected behaviour because the documentation states:

  --root-path TEXT                Set the ASGI 'root_path' for applications submounted below a given URL path.

The behaviour instead seems to be that uvicorn itself mounts the application in a subpath.

I guess a reasonable solution might be to have two separate options for those:

• --root-path which just only sets the root_path
• --mountpoint which actually serves the application in a subpath (both adjusting path and root_path)

[amol-]

PS: I'm happy to contribute a PR if we reach consensus over the behavior

[amol-]

An implementation has been proposed in #2493