Header names from scope not lowercased in datastructures.Headers constructor

[viccie30]

datastructures.Headers lowercases header names if constructed from a mapping of strings

starlette/starlette/datastructures.py

Line 505 in ad7ff08

self._list = [(key.lower().encode("latin-1"), value.encode("latin-1")) for key, value in headers.items()]

but not if constructed from an ASGI scope

starlette/starlette/datastructures.py

Line 512 in ad7ff08

self._list = scope["headers"] = list(scope["headers"])

According to the ASGI specification "header names should be lowercased, but it is not required".

I ran into this because I was testing some middleware by directly calling it instead of through a ASGI server. I spent more than an hour trying to figure out why headers["Authorization"] would throw an error when there definitely was an Authorization header in scope. I would suggest also lowercasing header names if Headers is constructed from a scope dictionary.

[Kludex]

I can see why it would be frustrating, but I can also see why the behavior is the way it is: scope["headers"] would be the same as passing the raw, which doesn't need to do the lower casing.

Also, both TestClient and httpx.AsyncClient (ASGI) do the lower casing of headers...

It's also the first time I see this complaint. I'd say the current behavior is fine.