[Fix #1565] Make Rails/Presence allow index access methods

This PR makes `Rails/Presence` allow index access methods.

Fixes #1565.

Author: koic

changelog/change_make_rails_presence_allow_index_access_methods.md

@@ -0,0 +1 @@
+* [#1565](https://github.com/rubocop/rubocop-rails/issues/1565): Make `Rails/Presence` allow index access methods. ([@koic][])

lib/rubocop/cop/rails/presence.rb

@@ -68,6 +68,7 @@ class Presence < Base
         extend AutoCorrector
 
         MSG = 'Use `%<prefer>s` instead of `%<current>s`.'
+        INDEX_ACCESS_METHODS = %i[[] []=].freeze
 
         def_node_matcher :redundant_receiver_and_other, <<~PATTERN
           {
@@ -140,7 +141,7 @@ def ignore_other_node?(node)
         end
 
         def ignore_chain_node?(node)
-          node.method?('[]') || node.method?('[]=') || node.arithmetic_operation? || node.comparison_method?
+          index_access_method?(node) || node.assignment? || node.arithmetic_operation? || node.comparison_method?
         end
 
         def message(node, replacement)
@@ -190,6 +191,10 @@ def chain_replacement(receiver, chain, left_sibling)
           replaced += "(#{chain.arguments.map(&:source).join(', ')})" if chain.arguments?
           left_sibling ? "(#{replaced})" : replaced
         end
+
+        def index_access_method?(node)
+          INDEX_ACCESS_METHODS.include?(node.method_name)
+        end
       end
     end
   end

spec/rubocop/cop/rails/presence_spec.rb

@@ -301,6 +301,12 @@
       RUBY
     end
 
+    it 'does not register an offense when chained method is attribute assignment' do
+      expect_no_offenses(<<~RUBY)
+        a.attribute = 42 if a.present?
+      RUBY
+    end
+
     it 'does not register an offense when chained method is an arithmetic operation' do
       expect_no_offenses(<<~RUBY)
         a.present? ? a + 42 : nil