Header values with leading/trailing whitespaces in HTTP/2 mode causes request failure instead of 400 Bad Request #348

MRE:

test.py

from bareasgi import Application, HttpRequest, HttpResponse, text_writer
app = Application()

@app.on_http_request({'GET'}, '/')
async def example_handler(request: HttpRequest) -> HttpResponse:
    print(request.scope['headers'])
    return HttpResponse(
        200,
        [(b'content-type', b'text/plain')],
        text_writer('Hello world')
    )

hypercorn --certfile cert.pem --keyfile key.pem --bind 0.0.0.0:8443 --insecure-bind 0.0.0.0:8080 test:app

In HTTP/2 HTTPS mode, if a header value with leading/trailing whitespace is supplied, the connection is terminated abnormally. (For example, Postman gives HTTP/2 Protocol Error: Session closed with an error., and C# gives The response ended prematurely while waiting for the next frame from the server. (ResponseEnded))

While not continuing the process the request is correct, the way this is done is not conformant to RFC 9113, which states that in this case a 400 Bad Request should be returned to the client:

When a request message violates one of these requirements, an implementation SHOULD generate a 400 (Bad Request) status code (see Section 15.5.1 of [HTTP]), unless a more suitable status code is defined or the status code cannot be sent (e.g., because the error occurs in a trailer field).

We have identified the issue to be on hyperhorn side, as replacing bareasgi to fastapi does not resolve the issue, and setting up a similar HTTP/2 server on other technology (e.g Node.JS) will not replicate this issue.