Allow app-dir parameter on the run() function

[Kludex]

Closes #1126

[Kludex]

@HansBrende You recommended the solution, so feel free to review as well. 🙏

[HansBrende]

LGTM!

[Kludex]

@euri10 ping

[euri10]

I think this looks good, the only small thing that may make it better is adding a test, I realize original PR that introduced the feature doesn't have one either so we're naked here and this will hit when working again on coverage anyway.
So approved, but feel free to add tests ;)

[Kludex]

I will add, thanks. ✌️

[Kludex]

How would you test this?

I started with this thought:

def test_app_dir(tmp_path: Path, caplog: pytest.LogCaptureFixture) -> None:
    app_dir = tmp_path / "dir" / "app_dir"
    app_file = app_dir / "main.py"
    app_dir.mkdir(parents=True)
    app_file.touch()
    app_file.write_text(
        dedent(
            """
            async def app(scope, receive, send):
                ...
            """
        )
    )
    run("main:app", app_dir=str(app_dir))

But the server will run, and we don't want that. We use run_server in similar cases.

After that I thought: "we'll, let's mock the server.run. But if I do that, we'll not test that we reached the import_string successfully...

Ideas?

[humrochagf]

Hi!

You can try to use the way I did for the cli tools https://github.com/encode/uvicorn/blob/master/tests/test_cli.py#L69-L78
Mock just the Config.bind_socket and Server.run to prevent the actual server from running and also from locking the socket.

Then you can check sys.path to validate the app_dir path was added to it

[Kludex]

I'm going to add the test suggested by @humrochagf (thanks).

But that's not fully what I want. I want to be able to know that app was imported. But to do that, I'll have to complicate things.