Reusing caches from Merge Queue checks?

[siketyan]

I am using actions/cache in a Merge Queue enabled repository. The Merge Queue checks work instead of checks by push trigger.

Usually actions/cache reuses caches from main branch when running on a topic branch or pull request merge (refs/pull/<number>/merge). However, caches are not reused from Merge Queue checks (gh-readonly-queue/main/<ref>). It would be great if I can assume the gh-readonly-queue/main/* is a global scope; any other topic branches can reuse from caches from the refs.

Is there any workaround or something for this?

[tsvetomir]

Are you sure you have a populated cache in your main branch?

I was having a similar issue, but it turned out that I've never added a cache entry from the main branch. Once this was sorted, the cache was accessible to the action in the merge queue.

[jdelStrother]

I believe the problem @siketyan & I are are experiencing is different - the merge queue can re-use a cache from the main branch, but it then saves a cache on the gh-readonly-queue/main/foo branch, which is effectively useless. Any work done to generate that cache can't be re-used by the main branch or a new gh-readonly-queue/main/bar branch, so they have to do it all over again.

[siketyan]

@jdelStrother Indeed that's the problem I am experiencing. We need to run the workflow both on merge queue trigger and push trigger just for caching, or we can't get any cache on each run.

[siketyan]

AFAIK every commit in a merge queue must be linear, and safe to skip checks after they passed the CI and got merged. We can also run it again on the main branch for cache, wasting computing resources and our money.

It will be great if we can share the cache at least among runs on the queue. As we don't need to run push trigger on the main branch anymore if merge queue is enforced, I actually want to use the cache on pull requests that is populated on the merge queue for the base branch.

[jdelStrother]

Yeah. I'm wondering if I need to replace some of our actions/cache usage with actions/{upload,download}-artifact to get around this