Uvicorn skipped the first request

[nggit]

In my tests, Uvicorn does not respond to the first valid request, when the second request is bad.

I don't know if this is by design or a bug.

~> printf 'GET / HTTP/1.1\r\nHost: localhost\r\n\r\nGET HTTP/1.1\r\n\r\n' | nc 127.0.0.1 8000
HTTP/1.1 400 Bad Request
date: Mon, 12 May 2025 04:18:27 GMT
server: uvicorn
content-type: text/plain; charset=utf-8
content-length: 30
connection: close

Works as expected with --http h11:

~> printf 'GET / HTTP/1.1\r\nHost: localhost\r\n\r\nGET HTTP/1.1\r\n\r\n' | nc 127.0.0.1 8000
HTTP/1.1 200 OK
date: Mon, 12 May 2025 04:29:50 GMT
server: uvicorn
content-type: text/plain
Transfer-Encoding: chunked

d
Hello, World!
0

HTTP/1.1 400 Bad Request
content-type: text/plain; charset=utf-8
connection: close
Transfer-Encoding: chunked

1e
Invalid HTTP request received.
0

Running uvicorn 0.34.2 with CPython 3.12.9 on Linux and httptools 0.6.4.

# example.py
async def app(scope, receive, send):
    assert scope['type'] == 'http'

    await send({
        'type': 'http.response.start',
        'status': 200,
        'headers': [
            (b'content-type', b'text/plain'),
        ],
    })
    await send({
        'type': 'http.response.body',
        'body': b'Hello, world!',
    })