Lefthook doesn't block commits when using a --fix or --write option.

[ava-mc]

🔧 Summary

When adding linting checks for pre-commit (e.g. prettier, eslint, markdownlint) using the --fix option, the commit still goes through and fixes the file afterwards.

Lefthook version

Using lefthook version 1.3.2

Steps to reproduce

Commit file with fixable linting error, when having a linting check in pre-commit with the --fix option.

Expected results

If a file is automatically fixed by resolving the linting issues, I would want my commit to still be blocked, but fix the file.

Only way to circumvent this for the moment: do 2 separate checks: one purely for verifying, and one for fixing. However, this decreases the speed of the pre-commit checking a lot.

Actual results

Commit with linting mistakes still goes through, while file is fixed.

Possible Solution

Either on the side of the specific packages: add error code when fixes are executed
For lefthook: keep track when fix has happened and give the option to block commits in these types of cases.

(Specifically for prettier: there is a package pretty-quick that gives the option to --bail when a fix happens and still block the commit, but such a solution is not available for each linter.)

[mrexox]

Hey @ava-mc! It's a good idea but I have concerns about the solution. The reason lefthook doesn't block commits is - the linter's return code is 0, so it finishes successfully. Many people want lefthook to behave smoothly and add changes for fixed files automatically.

I can recommend you the following configuration to get what you want:

pre-commit:
  commands:
    lint:
      # it looks like a hack but it makes sense that commands should fail (return non-0) to fail the hook
      run: npm run lint || (npm run lint --fix && exit 1)

Or if you want to automatically add fixed files to the commit, use the following:

pre-commit:
  commands:
    lint:
      run: npm run lint {staged_files} --fix && git add {staged_files}

I am going to add an auto-add changes files option, but still can't decide on naming. Anyway, please write if this works for you.

[pvds]

@mrexox great that you're planning to add an "auto-add changed files" option.

I would suggest that as long as #64 has not been implemented/merged the documentation is updated with your recommendations.

[pvds]

@mrexox I guess this issue can be closed since #64 is completed, allowing changed files to be added with https://github.com/evilmartians/lefthook/blob/master/docs/configuration.md#stage_fixed