httpx uses proxy unexpectedly on windows

[amchii]

Checklist

• The bug is reproducible against the latest release and/or master.
• There are no similar issues or pull requests to fix it yet.

Describe the bug

I set a proxy globally on 127.0.0.1:10909 but except for localhost/127.0.0.1(Windows Setting->Network->Proxy ), then I found httpx.get('http://127.0.0.1:8000') will use the proxy(unexpected), but chrome and requests.get('http://127.0.0.1:8000') accessed it directly(expected).

To reproduce

1. Set a proxy globally but except for localhost\127.0.0.1,
2. Exec httpx.get('http://127.0.0.1:8000') .

Expected behavior

httpx.get accesses http://127.0.0.1:8000 without proxy.

Actual behavior

httpx.get accesses http://127.0.0.1:8000 with proxy.

Debugging material

Environment

• OS: Windows 10
• Python version: 3.7.6
• HTTPX version: 0.17.0
• Async environment: no
• HTTP proxy: no
• Custom certificates: no

Additional context

[tomchristie]

We might need a bit of compare-and-contrast between what we do for determining environment proxies on httpx vs. what requests does.

Our case...

httpx/httpx/_utils.py

Line 287 in e05a537

def get_environment_proxies() -> typing.Dict[str, typing.Optional[str]]:

Theirs... https://github.com/psf/requests/blob/589c4547338b592b1fb77c65663d8aa6fbb7e38b/requests/utils.py#L770

[amchii]

They check the registry for the internetSettings and match the proxyOverride https://github.com/psf/requests/blob/8c211a96cdbe9fe320d63d9e1ae15c5c07e179f8/requests/utils.py#L64

[tomchristie]

Okay, so pretty sure we're going to want to escalate this one. Either so that we're documenting that we only use environment variables for our proxy env setup (so that we're more consistent cross-platform) or (more likely?) to add support for windows registry proxy settings.

[amchii]

Thanks!

And macosx: https://github.com/python/cpython/blob/3ba3d513b1e3c63d09cb798b982a9e6c369cea4c/Lib/urllib/request.py#L2638.
requests checks proxy-bypass setting for every certain request url, they can easily do this by calling urllib.request.proxy_pass(host). But httpx use httpx.Client._mounts to save the proxy-pattern when initialization for all request, with this approach, I think it's a little hard to mount the proxy-pass pattern , especially ip like '10.0/16'.

[tomchristie]

Escalated as #1536