New Cop idea: detect redundant all

[masato-bkn]

Is your feature request related to a problem? Please describe.

I often come across all used as receiver for Active Record query methods

User.all.order(:created_at)
User.all.find(id)

However, in these cases, the output is the same with or without all, so I think it's redundant and could be removed.

Describe the solution you'd like

I'd like to add a cop that remove all used as receiver of Active Record query methods.

Example

# bad
User.all.order(:created_at)
User.all.find(id)

# good
User.order(:created_at)
User.find(id)

Query methods to be checked

I am considering one of the following options for methods to be checked by this cop.

• frequently used query methods such as find, find_by, order, where, etc
• methods defined at https://github.com/rails/rails/blob/8c3b8bc59cbc6aa44f38ce51bfd5ff67ff6d38bc/activerecord/lib/active_record/querying.rb#L5, although there are many.

Additional context

If there's a positive reaction to this cop idea, I plan to submit a PR.

[mkllnk]

The release notes list this as bug fix but it should have been a new feature, right?

[koic]

@mkllnk I've fixed the incorrect entry in this commit: 3932c01 Thanks!