extensions.md

Extensions

It's possible to extend RuboCop with custom cops and formatters.

Loading Extensions

Besides the --require command line option you can also specify ruby files that should be loaded with the optional require directive in the .rubocop.yml file:

require:
 - ../my/custom/file.rb
 - rubocop-extension

!!! Note

The paths are directly passed to `Kernel.require`. If your
extension file is not in `$LOAD_PATH`, you need to specify the path as
relative path prefixed with `./` explicitly or absolute path. Paths
starting with a `.` are resolved relative to `.rubocop.yml`.

Custom Cops

You can configure the custom cops in your .rubocop.yml just like any other cop.

Writing your own Cops

See development.

Known Custom Cops

• rubocop-performance - Performance optimization analysis
• rubocop-rails - Rails-specific analysis
• rubocop-rspec - RSpec-specific analysis
• rubocop-thread_safety - Thread-safety analysis
• rubocop-require_tools - Dynamic analysis for missing require statements
• rubocop-i18n - i18n wrapper function analysis (gettext and rails-i18n)
• rubocop-sequel - Code style checking for Sequel gem
• cookstyle - Custom cops and config defaults for Chef Infra Cookbooks
• rubocop-rake - Rake-specific analysis

Any extensions missing? Send us a Pull Request!

Custom Formatters

You can customize RuboCop's output format with custom formatters.

Creating a Custom Formatter

To implement a custom formatter, you need to subclass RuboCop::Formatter::BaseFormatter and override some methods, or implement all formatter API methods by duck typing.

Please see the documents below for more formatter API details.

• RuboCop::Formatter::BaseFormatter
• RuboCop::Cop::Offense
• Parser::Source::Range

Using a Custom Formatter from the Command Line

You can tell RuboCop to use your custom formatter with a combination of --format and --require option. For example, when you have defined MyCustomFormatter in ./path/to/my_custom_formatter.rb, you would type this command:

$ rubocop --require ./path/to/my_custom_formatter --format MyCustomFormatter