downloads of github releases aren't cached

Environment

• pip version: 20.2
• Python version: 3.6.10
• OS: macOS

Description

Downloads of github release packages are not cached.

Expected behavior

Subsequent downloads read from the local cache, instead of downloading again.

How to Reproduce

$ python3 -m venv --clear /tmp/venv
$ /tmp/venv/bin/pip install --upgrade pip
Collecting pip
  Using cached https://files.pythonhosted.org/packages/36/74/38c2410d688ac7b48afa07d413674afc1f903c1c1f854de51dc8eb2367a5/pip-20.2-py2.py3-none-any.whl
Installing collected packages: pip
  Found existing installation: pip 18.1
    Uninstalling pip-18.1:
      Successfully uninstalled pip-18.1
Successfully installed pip-20.2

$ /tmp/venv/bin/pip install https://github.com/tekumara/spark/releases/download/v2.4.5-cloud/pyspark-2.4.5.tar.gz

Collecting https://github.com/tekumara/spark/releases/download/v2.4.5-cloud/pyspark-2.4.5.tar.gz
  Downloading https://github.com/tekumara/spark/releases/download/v2.4.5-cloud/pyspark-2.4.5.tar.gz (268.3 MB)
     |███████▌                        | 63.1 MB 4.5 MB/s eta 0:00:46

When the above is repeated, pyspark-2.4.5.tar.gz is downloaded again, rather than used from the cache.

[tekumara]

So if I use a named urlspec, pip will use the cached version rather than downloading it again:

$ pip install 'pyspark @ https://github.com/tekumara/spark/releases/download/v2.4.5-cloud/pyspark-2.4.5.tar.gz'
Processing /Users/tekumara/Library/Caches/pip/wheels/4d/8c/99/636fbcc2942d25483272d77c0654cd921907ff73717f7b5627/pyspark-2.4.5-py2.py3-none-any.whl
Collecting py4j==0.10.7
  Using cached py4j-0.10.7-py2.py3-none-any.whl (197 kB)
Installing collected packages: py4j, pyspark

This is using pip 20.2.3. Seems like a pretty workable solution.

[uranusjr]

@pfmoore Ah right, I confused this with the wheel cache rules, which does not apply here, of course. HTTP caching should be fine. Sorry.