pip download --no-deps should not attempt to load metadata

[SpecLad]

What's the problem this feature will solve?

Consider this:

$ pip download --no-deps psycopg2 --no-binary psycopg2
Collecting psycopg2
  Using cached psycopg2-2.9.3.tar.gz (380 kB)
  Preparing metadata (setup.py) ... error
  error: subprocess-exited-with-error

  × python setup.py egg_info did not run successfully.
  │ exit code: 1
  ╰─> [23 lines of output]
      running egg_info
      creating /tmp/pip-pip-egg-info-zff26g_c/psycopg2.egg-info
      writing /tmp/pip-pip-egg-info-zff26g_c/psycopg2.egg-info/PKG-INFO
      writing dependency_links to /tmp/pip-pip-egg-info-zff26g_c/psycopg2.egg-info/dependency_links.txt
      writing top-level names to /tmp/pip-pip-egg-info-zff26g_c/psycopg2.egg-info/top_level.txt
      writing manifest file '/tmp/pip-pip-egg-info-zff26g_c/psycopg2.egg-info/SOURCES.txt'

      Error: pg_config executable not found.

      [... snipped irrelevant details ...]

  note: This error originates from a subprocess, and is likely not a problem with pip.
error: metadata-generation-failed

× Encountered error while generating package metadata.
╰─> See above for output.

note: This is an issue with the package mentioned above, not pip.
hint: See above for details.

The requested distribution was downloaded, but, since pip failed to read its metadata, the command was aborted and the distribution was not saved. This failure seems unnecessary. Since --no-deps was specified, pip shouldn't have needed to fetch the metadata in the first place.

Describe the solution you'd like

pip download --no-deps should not attempt to read distribution metadata.

Alternative Solutions

I don't know of any tool other than pip that downloads distributions by name. If there is one that doesn't have this problem, that would probably satisfy me.

Additional context

The current behavior can be reproduced with pip 22.0.4.

Code of Conduct

• I agree to follow the PSF Code of Conduct.

[uranusjr]

duplicate of #1884