RuboCop

Role models are important.
-- Officer Alex J. Murphy / RoboCop

RuboCop is a Ruby code style checker based on the Ruby Style Guide.

Installation

RuboCop's installation is pretty standard:

$ gem install rubocop

Basic Usage

Running rubocop with no arguments will check all Ruby source files in the current folder:

$ rubocop

Alternatively you can pass rubocop a list of files and folders to check:

$ rubocop app spec lib/something.rb

For more details check the available command-line options:

$ rubocop -h

Command flag	Description
`-v/--version`	Displays the current version and exits
`-d/--debug`	Displays some extra debug output
`-e/--emacs`	Output the results in Emacs format
`-c/--config`	Run with specified config file
`-s/--silent`	Suppress the final summary

Configuration

The behavior of RuboCop can be controlled via the .rubocop.yml configuration file. The file can be placed either in your home folder or in some project folder.

RuboCop will start looking for the configuration file in the directory it was started in and continue its way up to the home folder.

The file has the following format:

Encoding:
  Enabled: true

LineLength:
  Enabled: true
  Max: 79

It allows to enable/disable certain cops (checks) and to alter their behavior if they accept any parameters.

One or more individual cops can be disabled locally in a section of a file by adding a comment such as

# rubocop:disable LineLength, StringLiterals
[...]
# rubocop:enable LineLength, StringLiterals

You can also disable all cops with

# rubocop:disable all
[...]
# rubocop:enable all

One or more cops can be disabled on a single line with an end-of-line comment.

for x in (0..19) # rubocop:disable AvoidFor

Compatibility

Unfortunately every major Ruby implementation has its own code analysis tooling, which makes the development of a portable code analyzer a daunting task.

RuboCop currently supports MRI 1.9 and MRI 2.0. Support for JRuby and Rubinius is not planned at this point.

Editor integration

Emacs

rubocop.el is a simple Emacs interface for RuboCop. It allows you to run RuboCop inside Emacs and quickly jump between problems in your code.

flycheck > 0.9 also supports RuboCop and uses it by default when available.

Other Editors

Here's one great opportunity to contribute to RuboCop - implement RuboCop integration for your favorite editor.

Contributors

Here's a list of all the people who have contributed to the development of RuboCop.

I'm extremely grateful to each and every one of them!

I'd like to single out Jonas Arvidsson for his many excellent code contributions as well as valuable feedback and ideas!

If you'd like to contribute to RuboCop, please take the time to go through our short contribution guidelines.

Converting more of the Ruby Style Guide into RuboCop cops is our top priority right now. Writing a new cop is a great way to dive into RuboCop!

Of course, bug reports and suggestions for improvements are always welcome. GitHub pull requests are even better! :-)

Changelog

RuboCop's changelog is available here.