rubocop-grep

It is a RuboCop extension to define your cop with regexps.

Sometimes you need a custom cop to detect a problem. For example, if you need a cop to detect your internal library, RuboCop's core rules are not helpful. But creating a new cop is not easy enough if you are not familiar with RuboCop. You need to know AST, RuboCop's API, and so on.

In this case, rubocop-grep can be helpful. You can create a custom cop only with a Regular expression! If a regexp is enough to detect your problem, this gem can be the best way to solve the problem.

Install the gem and add to the application's Gemfile by executing:

$ bundle add rubocop-grep --require=false

If bundler is not being used to manage dependencies, install the gem by executing:

$ gem install rubocop-grep

First of all, you need to tell RuboCop to load this extension.

Put this into your .rubocop.yml.

require: rubocop-grep

Alternatively, use the following array notation when specifying multiple extensions.

require:
  - rubocop-other-extension
  - rubocop-grep

Then, define your rule in .rubocop.yml like the following.

Grep/Grep:
  Rules:
    # The simplest rule definition. It warns if the regexp matches your code.
    - Pattern: '\bENV\b'
      Message: Do not refer ENV directly.

    # Pattern can be an array.
    - Pattern:
        - 'binding\.irb'
        - 'binding\.pry'
      Message: 'Debug code remains'

    # The pattern matches code comments with `MatchInComment: true` option (default: false).
    - Pattern: 'Rspec'
      Message: 'Rspec is a typo of RSpec'
      MatchInComment: true

There are some similar projects to solve similar problems. Probably you should use one of the similar projects instead of rubocop-grep.

You can simply use grep (1) command, or git grep (1).

• Pros
  • They are available in most environments.
  • You can use them for non-Ruby files too.
• Cons
  • They are not integrated with RuboCop.
    • rubocop-grep is fully integrated with RuboCop. It means you can integrate this gem out-of-the-box with CI, editors, and so on.
    • But you need to set up a workflow for grep (1) if you want to use it on CI.
  • They do not have a configuration file.
    • You can configure rubocop-grep with .rubocop.yml, but you cannot configure grep.

If regexp is enough for your problem and you do not need RuboCop integration, grep (1) is a good solution.

https://github.com/soutaro/querly

Querly is a gem to detect a problem by the original query language.

• Pros
  • The query is more powerful than regexp.
    • It is based on AST, so you can ignore whitespaces, the order of keyword arguments, and so on.
• Cons
  • They are not integrated with RuboCop.

If you need more powerful queries and you do not need RuboCop integration, Querly is a good solution.

https://github.com/sider/goodcheck

Goodcheck is a linter based on Regexp.

• Pros
  • It supports a tokenizer too.
    • If you use a tokenizer, you don't need to care about whitespaces.
  • You can use it for non-Ruby files too.
  • It has a configuration file.
• Cons
  • They are not integrated with RuboCop.

If regexp is enough for your problem and you do not need RuboCop integration, Goodcheck is a good solution.

You can also create a custom cop by yourself to solve your problem.

• Pros
  • Creating a custom cop is the most powerful approach in similar projects.
    • It can find any problem that can be detected statically.
• Cons
  • You need to know AST, RuboCop API, and so on.

If regexp is not enough for your problem and you are familiar with RuboCop, creating a custom cop is a good solution.

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/pocke/rubocop-grep.