Fix an infinite loop for Style/MultilineMethodSignature when line break after def

changelog/fix_infinite_loop_for_style_multiline_method_signature.md

@@ -0,0 +1 @@
+* [#12763](https://github.com/rubocop/rubocop/pull/12763): Fix an infinite loop for `Style/MultilineMethodSignature` when there is a newline directly after the def keyword. ([@earlopain][])

lib/rubocop/cop/style/multiline_method_signature.rb

@@ -38,6 +38,7 @@ def on_def(node)
 
         private
 
+        # rubocop:disable Metrics/AbcSize
         def autocorrect(corrector, node, begin_of_arguments)
           arguments = node.arguments
           joined_arguments = arguments.map(&:source).join(', ')
@@ -49,9 +50,17 @@ def autocorrect(corrector, node, begin_of_arguments)
             corrector.remove(range_by_whole_lines(arguments.loc.end, include_final_newline: true))
           end
 
-          corrector.remove(arguments_range(node))
+          arguments_range = arguments_range(node)
+          # If the method name isn't on the same line as def, move it directly after def
+          if arguments_range.first_line != opening_line(node)
+            corrector.remove(node.loc.name)
+            corrector.insert_after(node.loc.keyword, " #{node.loc.name.source}")
+          end
+
+          corrector.remove(arguments_range)
           corrector.insert_after(begin_of_arguments, joined_arguments)
         end
+        # rubocop:enable Metrics/AbcSize
 
         def last_line_source_of_arguments(arguments)
           processed_source[arguments.last_line - 1].strip

lib/rubocop/rspec/expect_offense.rb

@@ -126,7 +126,7 @@ def expect_offense(source, file = nil, severity: nil, chomp: false, **replacemen
         @offenses
       end
 
-      # rubocop:disable Metrics/AbcSize, Metrics/MethodLength, Metrics/CyclomaticComplexity, Metrics/PerceivedComplexity
+      # rubocop:disable Metrics/AbcSize, Metrics/MethodLength, Metrics/CyclomaticComplexity
       def expect_correction(correction, loop: true, source: nil)
         if source
           expected_annotations = parse_annotations(source, raise_error: false)
@@ -148,7 +148,6 @@ def expect_correction(correction, loop: true, source: nil)
 
           break corrected_source unless loop
           break corrected_source if @last_corrector.empty?
-          break corrected_source if corrected_source == @processed_source.buffer.source
 
           if iteration > RuboCop::Runner::MAX_ITERATIONS
             raise RuboCop::Runner::InfiniteCorrectionLoop.new(@processed_source.path, [@offenses])
@@ -163,7 +162,7 @@ def expect_correction(correction, loop: true, source: nil)
 
         expect(new_source).to eq(correction)
       end
-      # rubocop:enable Metrics/AbcSize, Metrics/MethodLength, Metrics/CyclomaticComplexity, Metrics/PerceivedComplexity
+      # rubocop:enable Metrics/AbcSize, Metrics/MethodLength, Metrics/CyclomaticComplexity
 
       def expect_no_corrections
         raise '`expect_no_corrections` must follow `expect_offense`' unless @processed_source

spec/rubocop/cop/style/multiline_method_signature_spec.rb

@@ -47,8 +47,29 @@ def foo(arg)
         RUBY
 
         expect_correction(<<~RUBY)
+          def foo
+          (bar)
+          end
+        RUBY
+      end
+
+      it 'registers an offense and corrects when closing paren is on the following line' \
+         'and multiple line breaks after `def` keyword' do
+        expect_offense(<<~RUBY)
           def
-          foo(bar)
+          ^^^ Avoid multi-line method signatures.
+
+
+          foo(bar
+              )
+          end
+        RUBY
+
+        expect_correction(<<~RUBY)
+          def foo
+
+
+          (bar)
           end
         RUBY
       end