Pip --proxy does not work for package dependencies if -r requirements.txt file is passed

[scorpi023]

Description

Running pip install -r requirements.txt --proxy http://company_proxy:port does not work when multiple packages are listed and if any of the package itself has a dependency of another package.
I do see there is a similar issue open here - #9691 but I cannot confirm if the root cause is the same.

1. [ ]

Expected behavior

Running pip install -r requirements.txt --proxy http://company_proxy:port should work for all packages in the requirements.txt file even if the package has a dependency on another one.

pip version

24.2

Python version

3.12.7

OS

Windows 11 26100

How to Reproduce

1. Make sure you are behind a proxy.
2. Write a file with multiple packages listed in requirements.txt with at least one package having a dependency like winevt.
3. Run pip install -r requirements.txt --proxy http://company_proxy:port
4. Packages without dependencies will install and the ones that need dependencies will fail with timeout with the following error - subprocess-exited-with-error.
   pip subprocess to install build dependencies did not run successfully.

Output

No response

Code of Conduct

• I agree to follow the PSF Code of Conduct.

[notatallshaw]

Thanks for reporting, I can confirm the same, it's actually a duplicate of this issue: #6018

The workaround is to set the environmental variables HTTP_PROXY / HTTPS_PROXY or PIP_PROXY