rbenv: use opt bin symlink in rehash script

[steinybot]

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rbenv equivalent to #75715

[carlocab]

Thanks, @steinybot.

Am I understanding this correctly? This change is meant to fix rbenv's hardcoded paths getting invalidated whenever rbenv's version is bumped here in homebrew/core. In particular, it means that it works out the same for a user if they get this update now, or get it at the next version bump. Or am I misunderstanding something here?

[steinybot]

This change is meant to fix rbenv's hardcoded paths getting invalidated whenever rbenv's version is bumped here in homebrew/core.

Yes this is correct.

In particular, it means that it works out the same for a user if they get this update now, or get it at the next version bump.

Yes in practice I think that is correct. The install will not fixing the paths directly, it fixes the rehash script which is what writes the paths. The user still has to run rehash to fix existing ruby installs (or if they install a new ruby version then those will have the correct paths). If this goes as a new revision then that is going to change the path from 1.1.2 to 1.1.2_1 which will break the path so they have to run rehash. If it goes in 1.1.3 then also have to run rehash.

[mislav]

This works, but it feels brittle. If the expression command -v rbenv changes even slightly within rbenv source, this workaround silently breaks.

[carlocab]

There are two potential sources of breakage:

1. The line we want to change stops using $(command -v rbenv).
2. libexec/rbenv-rehash starts using $(command -v rbenv) somewhere else we may not want to change.

Both seem sufficiently unlikely to me, but you'd know more about this than I do, of course. libexec/rbenv-rehash hasn't changed in years, and the relevant line we want to change has been there for even longer.

I'm not sure 2 is such a problem either, as I think I'm comfortable with using opt_bin/"rbenv" everywhere rbenv wants to do command -v rbenv.

1 should not be a problem as long as it doesn't happen simultaneously with 2, as the inreplace will error out when it is unable to do a replacement. We can avoid that by tightening the inreplace with more context from the line we actually want to replace.

[mislav]

Thanks for elaborating. I'm not opposed to this being merged. But I do not feel like the fix is ideal in the long term. The main problem is that Homebrew aggressively prunes old versions of software after upgrades. This breaks not just rbenv, but also ruby gems linked to removed versions of Homebrew software that got updated in the meantime. I have fixed my own Ruby development environment with export HOMEBREW_NO_INSTALL_CLEANUP=true

[steinybot]

Hopefully such a change wouldn't break silently and would be picked up by the test.

[github-actions]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.

[carlocab]

Sorry for the delayed review on this -- I'm thinking we can drop the revision and merge this without bottles so we can apply this change to the next version bump.

Making this change with the revision now means discarding the high_sierra bottle, which seems a bit wasteful to me, since this isn't really meant to do anything until rbenv gets a version bump.

[jonchang]

ping @carlocab, I've resolved the merge conflicts here and dropped the revision line.

[carlocab]

Thanks @jonchang, @steinybot!

[BrewTestBot]

🤖 A scheduled task has triggered a merge.

[mislav]

Thank you @steinybot @jonchang for fixing this and @carlocab for reviewing! ❤️