I remember avoiding this because of some quirks. But can't recall why exactly.. I'll try to look into this.

OK, on other repos the cache wasn't working correctly with the old cache action, and setup-python worked first time (I think it's aiohttp-demos which takes about 10 mins extra without caching).

@Dreamsorcerer

OK, on other repos the cache wasn't working correctly with the old cache action

One common mistake is making checkout prior to invoking cache. Check for that first.

I remember avoiding this because of some quirks. But can't recall why exactly.. I'll try to look into this.

I tried to recall what were the corner cases. And I found two:

1. Skipping caching for release CI/CD invocations — this allows to catch weird cases that don't come up in PRs because they use older versions of packages, for example: https://github.com/cherrypy/cheroot/blob/0fd16f0/.github/workflows/ci-cd.yml#L246-L247
2. Skipping caching for unstable/nightly/dev Python jobs, especially in the period when CPython transitions between alpha/beta/rc. This is because older package versions may be picked up by pip earlier and the, they'd break when GitHub updates their CPython alpha build but the cached packages aren't updated. Example: https://github.com/cherrypy/cheroot/blob/0fd16f0/.github/workflows/ci-cd.yml#L717-L775.

FTR, the caching works as it is configured today: https://github.com/aio-libs/aiohttp/actions/runs/7688751163/job/20950541567#step:5:25.

It doesn't implement those stable ABI-conditional hacks, though. Would be nice to have them here too.

CodSpeed Performance Report

Merging #7442 will not alter performance

_{Comparing Dreamsorcerer-patch-2 (ad21bc0) with master (5a1c3be)}

Summary

✅ 14 untouched benchmarks

Test (3.13, Y, ubuntu, false)
setup-python-Linux-x64-22.04-Ubuntu-python-3.13.0-pip-16df3627115a202aec77821077e7df01ad7900a81e1096da766b5297341a202b

Test (3.13, ubuntu, false)
setup-python-Linux-x64-22.04-Ubuntu-python-3.13.0-pip-16df3627115a202aec77821077e7df01ad7900a81e1096da766b5297341a202b

no-extensions isn't considered in the cache key

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.67%. Comparing base (5a1c3be) to head (ad21bc0).
Report is 1 commits behind head on master.

✅ All tests successful. No failed tests found.

@@            Coverage Diff             @@
##           master    #7442      +/-   ##
==========================================
+ Coverage   98.65%   98.67%   +0.01%     
==========================================
  Files         117      117              
  Lines       35893    35893              
  Branches     4260     4260              
==========================================
+ Hits        35410    35417       +7     
+ Misses        324      320       -4     
+ Partials      159      156       -3     

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no-extensions isn't considered in the cache key

Is that important, though? Wouldn't the deps be mostly the same in both cases?

@Dreamsorcerer I finally have the preferred solution to show: aio-libs/frozenlist#622. Let's replicate it instead.