node_modules caching in GitHub Actions often fails

[peterbe]

I noticed something strange. A lot of times, when .github/workflows/pr-test.yml runs it's unable to benefit from caching the whole ./node_modules directory between caches. That's strange. I would expect the cache to be constantly busted when the yarn.lock changes on all those Dependabot upgrades of @mdn/yari. But that was not the case.

You often see this:

By hopeful intuition and skimming a lot of the threads in this issue: actions/toolkit#658
It seems that it's failing because the cache key is not unique between workflows. E.g. pr-test.yml and pr-check_redirects.yml share the same cache key.

[peterbe]

Ah! Much better!