Python: Fix header conversion to byte-pair on scope building

[morgan9e]

headers: These are byte strings of the exact byte sequences sent by the client/to be sent by the server. While modern HTTP standards say that headers should be ASCII, older ones did not and allowed a wider range of characters. Frameworks/applications should decode headers as they deem appropriate.
(https://asgi.readthedocs.io/en/latest/specs/www.html#wsgi-compatibility)

Workerd uses Pyodide JSProxy object when passing fetch(request, env) to Python, but JSProxy objects translates into string, not byte-string.

In order to match ASGI specification, it needs to be translated into byte-pair when building scopes.

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[morgan9e]

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[hoodmane]

Code change makes sense. Ideally we ought to add a test.

[hoodmane]

In lieu of adding a test, can we add a comment here with an example that cares about this being bytes so that we can add a test ourselves later?

[morgan9e]

It assumes FastAPI so that would be a main concern, but its for ASGI spec though so should I add for FastAPI or just asserting for spec?

Like, anything for

@app.get("/example")
  async def example(request: Request):
    request.headers.get("content-type") # this will error if header is not bytes.

perhaps?

[morgan9e]

Also is there way to test this locally? I want to build miniflare with master workerd, but building workers-sdk doesnt works..

[hoodmane]

You can build workerd by itself and then set an environment variable to tell wrangler to use your custom build. @dom96 are there good instructions somewhere that we can point contributors to?

I guess I should check it out and test it myself...

[dom96]

May be easier to build and run workerd locally. These are probably the best instructions we have for doing this: https://github.com/cloudflare/workerd?tab=readme-ov-file#configuring-workerd.

We also have some sample Python worker configs in the repo already, for example https://github.com/cloudflare/workerd/tree/main/samples/pyodide-fastapi

[morgan9e]

Oh, so I can use workerd directly! Thanks, now I can test few things.