build cache / tsbuildinfo not used, but why?

[simllll]

TypeScript Version: 4.0.5 / also tested it with 4.1

Search Terms: build cache, incremental build, tsbuildinfo, timestamps

Issue

I'm using github actions for our tests, and would like to make use of the build cache to shorten runtime of the actions. But typescirpt is not using the buildcache. I tried already debugging:

• ensuring timestamps are identical from first job to 2nd job
• ensuring tsbuildcache is cached and all output files are too, and cache is restored correclty

What (else) is a factor to consider the build cache to be valid for tsc to re use it? Is there any possibility to debug why it's not using the cache? On our dev workstations everything is working perfectly.

Expected behavior: Typescript should use the buildcache

Actual behavior: It's not using the buildcache

[simllll]

I found some sort of answer, by using "--verbose" flag typescript outputs the reason why it's not using the cache.

[simllll]

Just in any case someone else is running into this too. I fixed my issue by using https://github.com/MestreLion/git-tools git-restore-mtime toolkit

      - name: Restore mtime for git checkout
        run: sudo apt install git-restore-mtime && sudo curl -o /usr/lib/git-core/git-restore-mtime https://raw.githubusercontent.com/MestreLion/git-tools/v2020.09/git-restore-mtime && git restore-mtime

this allow github actions to utilize typescripts caching strategy!

[simllll]

I've anyone stumpled upon this: see https://github.com/actions/cache/issues/459 for a possible solution