GitHub Actions CI keeps hitting and missing the edm package cache

[rahulporuri]

I'm not sure why the GitHub Actions CI isn't able to use the cache on any platform. See for example jobs on the PR https://github.com/enthought/enable/pull/599

• Linux + PyQt5 https://github.com/enthought/enable/runs/1937004829
• Mac OS + PyQt5- https://github.com/enthought/enable/pull/599/checks?check_run_id=1937005006
• Windows + PyQt5 https://github.com/enthought/enable/pull/599/checks?check_run_id=1937005141

On all three platforms, messages of the form below can be seen in the Cache EDM Packages step of the jobs.

Cache not found for input keys: macOS-pyqt5-ad8fc51d531ddbde3c34c7c037cc0b3105c6d1a1dd735c4cf83f06ea624cf4ed

[jwiggins]

This section of the docs has what I believe is the answer.

To fix this, I think we need to create an action which runs on the master branch after PRs are merged. If the hash-key has changed, do the normal CI run which builds the cache for that key, otherwise do nothing. Then all PRs branched from master where a cache exists will get the benefits of said cache.

Yes, this seems a bit overly complicated.

Note that this run has some jobs which hit a warm cache.