Rubocop: Support custom environment names for Rails/UnknownEnv

[ecbrodie]

It would be great if the Rails/UnknownEnv cop allowed for configuration for custom environment names that are acceptable for the application. For example, my application supports a "performance" Rails env, thus a call to the method Rails.env.performance? should be expected.

I envision this custom configuration being a YAML array of strings.

Expected behavior

Rubocop will not fail because there was custom configuration for the Rails/UnknownEnv cop that included the environment "performance" as a supported environment name.

Actual behavior

Rubocop fails due to the Rails/UnknownEnv cop disallowing code that calls Rails.env.performance?.

Steps to reproduce the problem

Run rubocop on a file that includes the code Rails.env.performance?.

RuboCop version

0.51.0 (using Parser 2.4.0.0, running on ruby 2.4.1 x86_64-darwin16)

[pocke]

http://rubocop.readthedocs.io/en/latest/cops_rails/#railsunknownenv
You can configure custom environments with .rubocop.yml.
For example:

Rails/UnknownEnv:
  Environments:
    - production
    - development
    - test
    - performance

Take care the default environments are also needed.

[VinyLimaZ]

This doesn't make sense! We already have a folder on config with all environments that the application has, why not use it to know what are the envs of the app?

[sethjeffery]

Probably the same reason Rubocop can't look at your code and assume that that's the way you intended to write it. If you create a config/environments/wibble.rb one can argue that you still should tell Rubocop that you _meant_ to stray away from standard practice.