[Fix rubocop#9767] Fix Style/ClassAndModuleChildren cop to preserve…

… comments

Closes rubocop#9767

changelog/fix_class_and_module_children_preserve_comment.md

@@ -0,0 +1 @@
+* [#9767](https://github.com/rubocop/rubocop/issues/9767): Fix `Style/ClassAndModuleChildren` cop to preserve comments. ([@tejasbubane][])

lib/rubocop/cop/style/class_and_module_children.rb

@@ -87,9 +87,18 @@ def compact_definition(corrector, node)
         end
 
         def compact_node(corrector, node)
-          replacement = "#{node.body.type} #{compact_identifier_name(node)}"
           range = range_between(node.loc.keyword.begin_pos, node.body.loc.name.end_pos)
-          corrector.replace(range, replacement)
+          corrector.replace(range, compact_replacement(node))
+        end
+
+        def compact_replacement(node)
+          replacement = "#{node.body.type} #{compact_identifier_name(node)}"
+
+          body_comments = processed_source.ast_with_comments[node.body]
+          unless body_comments.empty?
+            replacement = body_comments.map(&:text).push(replacement).join("\n")
+          end
+          replacement
         end
 
         def compact_identifier_name(node)

spec/rubocop/cop/style/class_and_module_children_spec.rb

@@ -129,6 +129,23 @@ module Baz
       RUBY
     end
 
+    it 'preserves comments' do
+      expect_offense(<<~RUBY)
+        # top comment
+        class Foo::Bar # describe Foo::Bar
+              ^^^^^^^^ Use nested module/class definitions instead of compact style.
+        end
+      RUBY
+
+      expect_correction(<<~RUBY)
+        # top comment
+        module Foo
+          class Bar # describe Foo::Bar
+          end
+        end
+      RUBY
+    end
+
     it 'accepts nested children' do
       expect_no_offenses(<<~RUBY)
         class FooClass
@@ -251,6 +268,29 @@ module Foo::Bar::Baz
       RUBY
     end
 
+    it 'preserves comments between classes' do
+      expect_offense(<<~RUBY)
+        # describe Foo
+        # more Foo
+        class Foo
+              ^^^ Use compact module/class definition instead of nested style.
+          # describe Bar
+          # more Bar
+          class Bar
+          end
+        end
+      RUBY
+
+      expect_correction(<<~RUBY)
+        # describe Foo
+        # more Foo
+        # describe Bar
+        # more Bar
+        class Foo::Bar
+        end
+      RUBY
+    end
+
     it 'accepts compact style for classes/modules' do
       expect_no_offenses(<<~RUBY)
         class FooClass::BarClass