Combining Reek and Overcommit

Posted by on April 5, 2017

My team has been using Overcommit for a while. We like how easy it makes it to set up Git commit hooks for the entire team and how easy it is to see what those hooks are.

Recently we decided to add Reek to our Code Quality process. To make it automatic we wanted to run Reek as part of our pre-commit hook. Overcommit already has a default hook for Reek, so making Reek run as part of every commit was super easy. Great!


When committing Reek warned us about smells that we couldn’t change. For example, Reek doesn’t like the default Rails migration syntax for a variety of (good) reasons. But my team isn’t going to change the Rails migration syntax so having Reek warn us about those changes wasn’t useful.

Reek offers many ways to silence these warnings. A recent addition is the exclude_paths configuration option. If you have this in your Reek config file

# Directories below will not be scanned at all
  - db/migrate

Then when you run reek . it won’t tell you about any smelly files in db/migrate. Hooray!


When we ran Reek in our pre-commit hook it kept warning us about files in db/migrate. Why?

Well, what Overcommit does is ask Git for a list of all files that have changed. It then passes each of those files to Reek. So, if a file changes in db/migrate then Reek is run with

reek ./db/migrate/file_that_changed.rb

And Reek’s behavior is to always check a file if given a path to a specific file. Even if the file is in an excluded directory.


After checking if it was cool with the Reek team we submitted a couple of PRs that gave Reek a new option --force-exclusion. We chose the flag name because it’s the same one used by Rubocop. Might as well be consistent. The flag tells Reek to ignore files in an excluded path, even when provided the path to a specific file. This work has been merged into Reek as of version 4.6.0, though you probably want 4.6.1 because of a bug with absolute paths.

For Overcommit to use the new flag you’ll need to update your .overcommit.yml file:

    enabled: true
    flags: ['--single-line', '--no-color', '--force-exclusion']

If you skip that part Reek will not use the new flag and you’ll still get warnings about files in excluded paths.

Now you can easily combine the great work of the Reek and Overcommit teams. Thanks to them for managing such helpful projects!