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Cop ideas #2

pocke opened this issue Jan 1, 2020 · 2 comments

Cop ideas #2

pocke opened this issue Jan 1, 2020 · 2 comments


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@pocke pocke commented Jan 1, 2020

Feel free to comment cop ideas with type.

  • Prefer find_each over each
    • We already have Rails/FindEach
  • Check method executes SQL usage in view.
    • AR::Base.where is not allowed in view
    • Detect method call that returns AR::Relation
  • Check bool type argument receives type that is always truthy or falsy.
    • e.g. after_update :foo, if: -> { 1 + 1 }
    • The if's block requires bool type, but 1 + 1 is always truthy.
  • Prefer Hash#dig over Hash#[]
  • Improve Rails/SaveBang
  • find_by with bang or conditional rubocop-hq/rubocop-rails#167
  • Detect unreachable code with bot type
  • Rails/DynamicFindBy without false positives
  • truthy type in conditional
  • Replacement of Style/BracesAroundHashParameters
    • ref: rubocop-hq/rubocop#7643
    • Maybe we can provide a cop for methods that receive both of keyword arguments and a hash.
  • Method aliases
    • find vs detect, map vs collect, etc...
  • Replace String#first and comparison with String#start_with?.
    • #2 (comment)
    • It is faster.
    • String#frist is added by ActiveSupport
  • AR::Relation#pluck vs AR::Relation#select for sub-query
    • rel.where(id: rel2.pluck(:id))
    • We may be able to reduce query with replacing pluck with select, but it depends on context.
  • send with public method name
    • foo.send(:foo_public_method) should be foo.foo_public_method
  • str[/substr/]should be str['substr']
    • Maybe typing is overkill?

I already search the following sources to find cop ideas.


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@koic koic commented Feb 6, 2020

This comment is inspired by the following commit in the rails/rails repository.

Performance/StartWith cop would be extended with the following example if RuboCop can detect a receiver type is the String type.

# bad
receiver.first == 'str'

# good


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@pocke pocke commented Feb 7, 2020

Thanks for your comment, @koic !

I'll add your idea to the checklist.

By the way, I guess your example code does not work well because String#first returns the first character, but it compares with 'str' in your example.
Probably it should be receiver.first == 's'.

And I confirmed String#first is added by ActiveSupport.


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