Merge pull request #972 from koic/mark_rails_find_each_as_unsafe

[Fix #694] Mark `Rails/FindEach` as unsafe

Author: koic

changelog/change_mark_rails_find_each_as_unsafe.md

@@ -0,0 +1 @@
+* [#694](https://github.com/rubocop/rubocop-rails/issues/694): Mark `Rails/FindEach` as unsafe. ([@koic][])

config/default.yml

@@ -460,8 +460,9 @@ Rails/FindEach:
   Description: 'Prefer all.find_each over all.each.'
   StyleGuide: 'https://rails.rubystyle.guide#find-each'
   Enabled: true
+  Safe: false
   VersionAdded: '0.30'
-  VersionChanged: '2.9'
+  VersionChanged: '<<next>>'
   Include:
     - app/models/**/*.rb
   AllowedMethods:

lib/rubocop/cop/rails/find_each.rb

@@ -3,8 +3,12 @@
 module RuboCop
   module Cop
     module Rails
-      # Identifies usages of `all.each` and
-      # change them to use `all.find_each` instead.
+      # Identifies usages of `all.each` and change them to use `all.find_each` instead.
+      #
+      # @safety
+      #   This cop is unsafe if the receiver object is not an Active Record object.
+      #   Also, `all.each` returns an `Array` instance and `all.find_each` returns nil,
+      #   so the return values are different.
       #
       # @example
       #   # bad