Merge pull request #1448 from ydakuka/1446/fix-incorrect-autocorrect-for-rails-delegate-when-module_function-is-used

[Fix #1446] Fix false positives for `Rails/Delegate` when `module_function` is used

Author: koic

changelog/fix_false_positives_for_rails_delegate_when_module_function_is_used.md

@@ -0,0 +1 @@
+* [#1446](https://github.com/rubocop/rubocop-rails/issues/1446): Fix false positives for `Rails/Delegate` when `module_function` is used. ([@ydakuka][])

lib/rubocop/cop/rails/delegate.rb

@@ -74,6 +74,7 @@ class Delegate < Base
         def on_def(node)
           return unless trivial_delegate?(node)
           return if private_or_protected_delegation(node)
+          return if module_function_declared?(node)
 
           register_offense(node)
         end
@@ -163,6 +164,12 @@ def private_or_protected_delegation(node)
           private_or_protected_inline(node) || node_visibility(node) != :public
         end
 
+        def module_function_declared?(node)
+          node.each_ancestor(:module, :begin).any? do |ancestor|
+            ancestor.children.any? { |child| child.send_type? && child.method?(:module_function) }
+          end
+        end
+
         def private_or_protected_inline(node)
           processed_source[node.first_line - 1].strip.match?(/\A(private )|(protected )/)
         end

spec/rubocop/cop/rails/delegate_spec.rb

@@ -42,6 +42,28 @@ def foo
     RUBY
   end
 
+  it 'does not find trivial delegate to `self` for separate `module_function` def' do
+    expect_no_offenses(<<~RUBY)
+      module A
+        module_function
+
+        def foo
+          self.foo
+        end
+      end
+    RUBY
+  end
+
+  it 'does not find trivial delegate to `self` for inline `module_function` def' do
+    expect_no_offenses(<<~RUBY)
+      module A
+        module_function def foo
+          self.foo
+        end
+      end
+    RUBY
+  end
+
   it 'finds trivial delegate with prefix' do
     expect_offense(<<~RUBY)
       def bar_foo