Using rubocop with -a option.

[skywinder]

I try to use rubocop with -a (--auto-correct) option to fix all minor issues automatically.

I try to put in the .overcommit.yml file strings like

PreCommit:
  RuboCop:
    enabled: true
    command: ['rubocop', '-a'] 
    #or this:
    #command: ['bundle', 'exec', 'rubocop', '-a'] 
    on_warn: fail # Treat all warnings as failures

But it's not apply fixes to files before commit.

So, questions is:
How to run rubocop -a before pre-commit checks automatically? Is there any option for it in overcommit project?

[jawshooah]

You'll have to write a custom hook to accomplish this, since the built-in RuboCop hook is intended simply to report errors, not to alter files before commit.

[skywinder]

@jawshooah yes, but i send another parameter to rubocop command (as you can see in example above), that run with -a --auto-correct option should also fix warnings. What I missed?

[jawshooah]

The core problem is that any changes rubocop --auto-correct makes are never staged. Overcommit sets up the hook environment by stashing all changes but keeping the index, runs the hooks, then restores the environment by doing a hard reset and re-applying the stash.

Actually, I'm not sure that you could even accomplish what you want with a custom hook at all, since restoring the environment wipes out any changes made during the hook run. @sds, can you think of a way around this?

[sds]

@skywinder Overcommit is not intended to run hooks that modify any files or add/remove files from the git index. It's not really an intended use case due to technical details of how we implement the pre-commit hook saving and restoring of the working tree.

It also keeps the tool open to supporting cool features in future like running hooks in parallel (#144) — the moment you start to encourage hooks to modify files you provide more ways for a user to shoot themselves in the foot since you have multiple actors (hooks) modifying a shared resource (the git index).

My recommendation is your custom hook should simply print out the command that should be run to auto correct the offenses if it finds any. Hope that helps.

[skywinder]

@sds thanks for clarifying! It's definitely makes sense!

[janwerkhoven]

Sorry that's not helpful at all. The rubocop --auto-correct command is one of the most useful of them all. Nobody wants to dive in and indent, remove spaces and refactor syntax manually. Rubocop does this excellently FOR YOU. Overcommit should allow such commands.

[jawshooah]

@janwerkhoven What @sds explained above is that preserving file modifications during hook runs would require a significant overhaul of Overcommit's internals, and it just isn't worth it to support this one use-case. Especially when you can accomplish the same thing by just running rubocop --auto-correct yourself when Overcommit notifies you of errors on commit.

[sds]

We're tracking adding support for pre-commit hooks with file-changing side effects in #238. It's definitely something we know will be useful. Open to well-tested pull requests for those who want it sooner rather than later!