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.

Installation

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

Usage

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

Similar Projects

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

grep (1)

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.

Querly

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.

Goodcheck

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.

Creating a custom cop by yourself

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.

Development

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.

Contributing

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