rubocop

README.md

A Ruby static code analyzer, based on the community Ruby style guide.

Title	Link
Github	https://github.com/rubocop-hq/rubocop
Docs	http://rubocop.readthedocs.io/en/latest/
Ruby Style Guide	https://github.com/rubocop-hq/ruby-style-guide

Contents:

• 1 Install gem
• 2 Usage
• 3 Configuration
• 4 Common offences

1 Install gem

Add to your Gemfile:

group :development do
  gem 'rubocop', '~> 0.57.1', require: false
end

Run bundle install.

2 Usage

In your project directory, run rubocop. It will scan all the files at current level and nested below it for any violations of style guide.

3 Configuration

Create a file .rubocop.yml at root of project directory.

• 3.1 Metrics
• 3.2 General
• 3.3 Style
• 3.4 Lint

3.1 Metrics

Metrics cops deal with properties of the source code that can be measured, such as class length, method length, etc.

To set maximum allowed length of a line of code to 70, you can do:

# .rubocop.yml
Metrics/LineLength:
  Max: 70

To skip one or more files from being checked by this cop, you can define Exclude:

Metrics/LineLength:
  Exclude:
    - 'path/to/file'
    - 'path/to/another/file'

3.2 General

To disable a cop completely i.e. for all the files, you can configure it at global level:

Bundler/OrderedGems:
  Enabled: false

To disable all cops for a set of files, do:

AllCops:
  Exclude:
    - 'path/to/file'
    - 'path/to/another/file'

3.3 Style

# .rubocop.yml
Style/RescueModifier:
  Enabled: false

Style/SignalException:
  EnforcedStyle: semantic

Style/FileName:
  Exclude:
    - 'path/to/file'
    - 'path/**/*.rb'

Style/Documentation:
  Exclude:
    - 'path/to/file'

Style/EachWithObject:
  Exclude:
    - 'path/to/file'

Style/MultilineBlockChain:
  Exclude:
    - 'path/to/file'

3.4 Lint

# .rubocop.yml
Lint/HandleExceptions:
  Exclude:
    - 'path/to/file'

4 Common offences

4.1 Style/FrozenStringLiteralComment

Style/FrozenStringLiteralComment: Missing magic comment # frozen_string_literal: true.

As per this, you need to add a comment # frozen_string_literal: true to every ruby file at the top. You can ask rubocop to do it for you by running:

$ rubocop --auto-correct --only FrozenStringLiteralComment

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