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I guess the main prom that there is no standardisation for no_proxy and different libraries / os could work differently

Most of the libraries use stdlib implementation from Lib/urllib/request.py

Request use own implementation which supports CIDR blocks, but only for ipv4:

• requests ignores no_proxy which contains a IPv6 CIDR  psf/requests#6313

import os

os.environ["no_proxy"] = "localhost,127.0.0.1,10.0.0.0/8,172.16.1.*,1:2:3::/64"
os.environ["NO_PROXY"] = "localhost,127.0.0.1,192.168.1.0/16"

# stdlib implementation
from urllib.request import proxy_bypass_environment
# requests implementation
from requests.sessions import should_bypass_proxies

hosts = ("localhost", "127.0.0.1", "127.0.0.2", "10.0.0.0", "192.168.1.32", "172.16.1.2", "[1:2:3::4]")
for host in hosts:
    print(f" {host} ".center(80, '='))
    print(f"stdlib Proxy Bypass Environment: {proxy_bypass_environment(host, None)}")
    print(f"requests Proxy Bypass Environment: {should_bypass_proxies(f"http://{host}", None)}")

================================== localhost ===================================
stdlib Proxy Bypass Environment: True
requests Proxy Bypass Environment: True
================================== 127.0.0.1 ===================================
stdlib Proxy Bypass Environment: True
requests Proxy Bypass Environment: True
================================== 127.0.0.2 ===================================
stdlib Proxy Bypass Environment: False
requests Proxy Bypass Environment: False
=================================== 10.0.0.0 ===================================
stdlib Proxy Bypass Environment: False
requests Proxy Bypass Environment: True
================================= 192.168.1.32 =================================
stdlib Proxy Bypass Environment: False
requests Proxy Bypass Environment: False
================================== 172.16.1.2 ==================================
stdlib Proxy Bypass Environment: False
requests Proxy Bypass Environment: False
================================== [1:2:3::4] ==================================
stdlib Proxy Bypass Environment: False
requests Proxy Bypass Environment: False

I don't know what is supposed to be happen in case if we change library in the future, e.g. from requests to urllib3, or use aiohttp in case if we turn internal code to async implementation (asyncio / anyio / trio)

So probably it is fine for replace httpx by requests, and I'm pretty sure that in past this was called by requests before we temporary remove usage of requests due to licence issue: #15781. However there is should not be a commitment that this behaviour remaining the same in the future, because this part of the code usually can't be changed without monkey patching third-party library / stdlib

@hussein-awala @Taragolis
I've added test code, but since the code might change in the future like #39799 (comment), I'm dissatisfied with dependency on requests library in the test code.
Is it appropriate to set up a temporary proxy app fixture to run in background for writing test?
It seems a bit too much for test

Is it appropriate to set up a temporary proxy app fixture to run in background for writing test?
It seems a bit too much for test

I would not spend a time for writing a test proxy. If there is any changes in the future then this test should be adopted by someone who will made this changes. About new library, it just a potential scenario but maybe it is never happen.

I believe, this is the last httpx use in Airflow core - httpx is used in a few other scripts and API client (and it could be easily replaced by requests as well), so we could get rid of httpx dependency in hatch_build.py.

I believe, this is the last httpx use in Airflow core - httpx is used in a few other scripts and API client (and it could be easily replaced by requests as well), so we could get rid of httpx dependency in hatch_build.py.

On the other hand with -> #40256 it turned out that we have some implicit dependencies on httpx in core, so removing it is not good idea.

Awesome work, congrats on your first merged pull request! You are invited to check our Issue Tracker for additional contributions.