Feature request: don't cache specified gems and/or clear whole bundler cache

[igneus]

Using setup-ruby with bundler-cache: true I now have in the cache a gem with native extensions, which are "broken" (successfully compiled, but against a set of C libraries other than I need). It seems to be impossible to replace contents of the cache. Even if Gemfile.lock changes, gems already present in the cache are reused and only missing ones installed, which is usually extremely useful, but not when you desperately need to rebuild the broken gem.

Would it be possible to add a new option, accepting a list of gems and excluding them from caching? E. g.

# ...
- uses: ruby/setup-ruby@v1
  with:
    ruby-version: 3.0.0
    bundler-cache: true
    #bundler-cache-exclude: # the new option I dream about
    #  - mysql2
    #  - nokogiri

    # EDIT: turns out that only simple string values are supported as action inputs
    bundler-cache-exclude: mysql2 nokogiri

For gems which are not self-contained, but depend on the build environment (like all gems with native extensions) this would occasionally be very useful.

If not, would it be possible to provide at least some mechanism for clearing the whole cache?

[igneus]

I've been trying to implement the bundler-cache-exclude option by deleting the gems in question from vendor/bundle after it is restored from cache, but my knowledge of Node.js is not up to the task. I can't make the code execute in correct order.

feature branch https://github.com/igneus/setup-ruby/tree/bundler-cache-exclude
test project https://github.com/igneus/ga-setup-ruby-test/actions

[eregon]

Why are the native extensions not working? (what's the error/output?) That's the real issue to solve.
The cache is meant to per platform (OS) and OS version, and that should be enough.
Are you using self-hosted runners or GitHub-hosted runners?

The cache is meant to work for native extensions too.

[eregon]

We could add a mechanism to manually change the version of the cache, but I don't think it would help you, the situation would just repeat again.

[igneus]

Why are the native extensions not working?

In the particular case I'm dealing with the mysql2 gem in cache is built with MySQL bindings, but it turned out we really need it to be built against MariaDB instead. Similar situations can happen with all those gems which can be compiled with various dependencies, based on what is available on the build system.

We could add a mechanism to manually change the version of the cache, but I don't think it would help you, the situation would just repeat again.

When I directly manage the cache, I usually solve misfortunes like this by making a meaningless modification to the cache key (e.g. adding some hardcoded string to the hash). Adding support for this would be another possible workaround.

[eregon]

Similar situations can happen with all those gems which can be compiled with various dependencies, based on what is available on the build system.

I see, that makes sense then.
If it was flags passed to Bundler to install gems we could maybe hash them, but if it's automatic detection no much chance.

Adding support for this would be another possible workaround.

Let's add that, it might be useful to diagnose issues and for that case.

Would you be interested to make a PR for it?
I'm thinking we should have a new input like cache-version (or cache-key-extra) which defaults to 0 and the user could specify 2 or so for it. It doesn't need to be a version, any string would do, but that's probably the easiest to present it.

[eregon]

Released as https://github.com/ruby/setup-ruby/releases/tag/v1.71.0