Mark Rails/Pluck as unsafe

Author: fatkodima

changelog/change_pluck_as_unsafe.md

@@ -0,0 +1 @@
+* [#826](https://github.com/rubocop/rubocop-rails/issues/826): Mark `Rails/Pluck` as unsafe. ([@fatkodima][])

config/default.yml

@@ -711,7 +711,9 @@ Rails/Pluck:
   Description: 'Prefer `pluck` over `map { ... }`.'
   StyleGuide: 'https://rails.rubystyle.guide#pluck'
   Enabled: 'pending'
+  Safe: false
   VersionAdded: '2.7'
+  VersionChanged: '<<next>>'
 
 Rails/PluckId:
   Description: 'Use `ids` instead of `pluck(:id)` or `pluck(primary_key)`.'

lib/rubocop/cop/rails/pluck.rb

@@ -9,6 +9,22 @@ module Rails
       # element in an enumerable. When called on an Active Record relation, it
       # results in a more efficient query that only selects the necessary key.
       #
+      # @safety
+      #   This cop is unsafe because model can define attribute aliases.
+      #
+      #   [source,ruby]
+      #   ----
+      #   class User < ApplicationRecord
+      #     alias_attribute :nickname, :name
+      #   end
+      #
+      #   # Original code
+      #   User.map { |user| user[:nickname] } # => array of nicknames
+      #
+      #   # After autocorrection
+      #   User.pluck(:nickname) # => raises ActiveRecord::StatementInvalid
+      #   ----
+      #
       # @example
       #   # bad
       #   Post.published.map { |post| post[:title] }