Improve offense message for Style/YodaExpression cop

lib/rubocop/cop/style/yoda_expression.rb

@@ -30,7 +30,7 @@ module Style
       class YodaExpression < Base
         extend AutoCorrector
 
-        MSG = 'Non literal operand should be first.'
+        MSG = 'Non-literal operand (`%<source>s`) should be first.'
 
         RESTRICT_ON_SEND = %i[* + & | ^].freeze
 
@@ -47,12 +47,12 @@ def on_send(node)
 
           return if offended_ancestor?(node)
 
-          add_offense(node) do |corrector|
+          message = format(MSG, source: rhs.source)
+          add_offense(node, message: message) do |corrector|
             corrector.swap(lhs, rhs)
           end
 
-          @offended_nodes ||= Set.new.compare_by_identity
-          @offended_nodes.add(node)
+          offended_nodes.add(node)
         end
 
         private
@@ -64,6 +64,10 @@ def supported_operators
         def offended_ancestor?(node)
           node.each_ancestor(:send).any? { |ancestor| @offended_nodes&.include?(ancestor) }
         end
+
+        def offended_nodes
+          @offended_nodes ||= Set.new.compare_by_identity
+        end
       end
     end
   end

spec/rubocop/cop/style/yoda_expression_spec.rb

@@ -6,7 +6,7 @@
   it 'registers an offense when using simple offended example' do
     expect_offense(<<~RUBY)
       1 + x
-      ^^^^^ Non literal operand should be first.
+      ^^^^^ Non-literal operand (`x`) should be first.
     RUBY
 
     expect_correction(<<~RUBY)
@@ -17,7 +17,7 @@
   it 'registers an offense and corrects when using complex offended example' do
     expect_offense(<<~RUBY)
       2 + (1 + x)
-      ^^^^^^^^^^^ Non literal operand should be first.
+      ^^^^^^^^^^^ Non-literal operand (`(1 + x)`) should be first.
     RUBY
 
     expect_correction(<<~RUBY)