Update Style/RedundantSort to be unsafe.

In an array where there are multiple elements where `a <=> b` == 0, or where the transformation done by the block has the same result, there will be a different element returned between `sort.last` and `max` (or `sort_by.last` and `max_by`), because `sort.last` will take the last element but `max` will return the first element. As such, this is not a safe change, as the specific element returned will change.

changelog/change_update_styleredundantsort_to_be_unsafe.md

@@ -0,0 +1 @@
+* [#10122](https://github.com/rubocop/rubocop/pull/10122): Update `Style/RedundantSort` to be unsafe, and revert the special case for `size` from [#10061](https://github.com/rubocop/rubocop/pull/10061). ([@dvandersluis][])

config/default.yml

@@ -4160,7 +4160,6 @@ Style/NumericLiteralPrefix:
     - zero_with_o
     - zero_only
 
-
 Style/NumericLiterals:
   Description: >-
                  Add underscores to large numeric literals to improve their
@@ -4481,6 +4480,8 @@ Style/RedundantSort:
                   `max_by` instead of `sort_by...last`, etc.
   Enabled: true
   VersionAdded: '0.76'
+  VersionChanged: <<next>>
+  Safe: false
 
 Style/RedundantSortBy:
   Description: 'Use `sort` instead of `sort_by { |x| x }`.'

lib/rubocop/cop/style/redundant_sort.rb

@@ -12,6 +12,33 @@ module Style
       # `Enumerable#max_by` can replace `Enumerable#sort_by` calls
       # after which only the first or last element is used.
       #
+      # @safety
+      #   This cop is unsafe, because `sort...last` and `max` may not return the
+      #   same element in all cases.
+      #
+      #   In an enumerable where there are multiple elements where `a <=> b == 0`,
+      #   or where the transformation done by the `sort_by` block has the
+      #   same result, `sort.last` and `max` (or `sort_by.last` and `max_by`)
+      #   will return different elements. `sort.last` will return the last
+      #   element but `max` will return the first element.
+      #
+      #   For example:
+      #
+      #   [source,ruby]
+      #   ----
+      #     class MyString < String; end
+      #     strings = [MyString.new('test'), 'test']
+      #     strings.sort.last.class   #=> String
+      #     strings.max.class         #=> MyString
+      #   ----
+      #
+      #   [source,ruby]
+      #   ----
+      #     words = %w(dog horse mouse)
+      #     words.sort_by { |word| word.length }.last   #=> 'mouse'
+      #     words.max_by { |word| word.length }         #=> 'horse'
+      #   ----
+      #
       # @example
       #   # bad
       #   [2, 1, 3].sort.first