Merge branch '50414-rubocop-rule-to-enforce-class-methods-over-module' into 'master'

Resolve "Make a Rubocop cop to prefer class_methods over ClassMethods for ActiveSupport::Concern"

Closes #50414

See merge request gitlab-org/gitlab-ce!21379

changelogs/unreleased/50414-rubocop-rule-to-enforce-class-methods-over-module.yml

+---
+title: Adds Rubocop rule to enforce class_methods over module ClassMethods
+merge_request: 21379
+author: Jacopo Beschi @jacopo-beschi
+type: added

lib/api/api_guard.rb

@@ -84,7 +84,7 @@ module API
       end
     end
-    module ClassMethods
+    class_methods do
       private
       def install_error_responders(base)

lib/api/projects_relation_builder.rb

@@ -2,7 +2,7 @@ module API
   module ProjectsRelationBuilder
     extend ActiveSupport::Concern
-    module ClassMethods
+    class_methods do
       def prepare_relation(projects_relation, options = {})
         projects_relation = preload_relation(projects_relation, options)
         execute_batch_counting(projects_relation)

lib/gitlab/github_import/representation/expose_attribute.rb

@@ -6,7 +6,7 @@ module Gitlab
       module ExposeAttribute
         extend ActiveSupport::Concern
-        module ClassMethods
+        class_methods do
           # Defines getter methods for the given attribute names.
           #
           # Example:

lib/gitlab/graphql/mount_mutation.rb

@@ -5,7 +5,7 @@ module Gitlab
     module MountMutation
       extend ActiveSupport::Concern
-      module ClassMethods
+      class_methods do
         def mount_mutation(mutation_class)
           # Using an underscored field name symbol will make `graphql-ruby`
           # standardize the field name

lib/static_model.rb

@@ -2,7 +2,7 @@
 module StaticModel
   extend ActiveSupport::Concern
-  module ClassMethods
+  class_methods do
     # Used by ActiveRecord's polymorphic association to set object_id
     def primary_key
       'id'

rubocop/cop/prefer_class_methods_over_module.rb

+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    # Enforces the use of 'class_methods' instead of 'module ClassMethods' for activesupport concerns.
+    # For more information see: https://gitlab.com/gitlab-org/gitlab-ce/issues/50414
+    #
+    # @example
+    #   # bad
+    #   module Foo
+    #     extend ActiveSupport::Concern
+    #
+    #     module ClassMethods
+    #       def a_class_method
+    #       end
+    #     end
+    #   end
+    #
+    #   # good
+    #   module Foo
+    #     extend ActiveSupport::Concern
+    #
+    #     class_methods do
+    #       def a_class_method
+    #       end
+    #     end
+    #   end
+    #
+    class PreferClassMethodsOverModule < RuboCop::Cop::Cop
+      include RangeHelp
+
+      MSG = 'Do not use module ClassMethods, use class_methods block instead.'
+
+      def_node_matcher :extend_activesupport_concern?, <<~PATTERN
+        (:send nil? :extend (:const (:const nil? :ActiveSupport) :Concern))
+      PATTERN
+
+      def on_module(node)
+        add_offense(node) if node.defined_module_name == 'ClassMethods' && module_extends_activesupport_concern?(node)
+      end
+
+      def autocorrect(node)
+        lambda do |corrector|
+          corrector.replace(module_range(node), 'class_methods do')
+        end
+      end
+
+      private
+
+      def module_extends_activesupport_concern?(node)
+        container_module = container_module_of(node)
+        return false unless container_module
+
+        container_module.descendants.any? do |descendant|
+          extend_activesupport_concern?(descendant)
+        end
+      end
+
+      def container_module_of(node)
+        while node = node.parent
+          break if node.type == :module
+        end
+
+        node
+      end
+
+      def module_range(node)
+        module_node, _ = *node
+        range_between(node.loc.keyword.begin_pos, module_node.source_range.end_pos)
+      end
+    end
+  end
+end

rubocop/rubocop.rb

@@ -7,6 +7,7 @@ require_relative 'cop/include_sidekiq_worker'
 require_relative 'cop/avoid_return_from_blocks'
 require_relative 'cop/avoid_break_from_strong_memoize'
 require_relative 'cop/line_break_around_conditional_block'
+require_relative 'cop/prefer_class_methods_over_module'
 require_relative 'cop/migration/add_column'
 require_relative 'cop/migration/add_concurrent_foreign_key'
 require_relative 'cop/migration/add_concurrent_index'

spec/rubocop/cop/prefer_class_methods_over_module_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+require 'rubocop'
+require 'rubocop/rspec/support'
+require_relative '../../../rubocop/cop/prefer_class_methods_over_module'
+
+describe RuboCop::Cop::PreferClassMethodsOverModule do
+  include CopHelper
+
+  subject(:cop) { described_class.new }
+
+  it 'flags violation when using module ClassMethods' do
+    expect_offense(<<~RUBY)
+      module Foo
+        extend ActiveSupport::Concern
+
+        module ClassMethods
+        ^^^^^^^^^^^^^^^^^^^ Do not use module ClassMethods, use class_methods block instead.
+          def a_class_method
+          end
+        end
+      end
+    RUBY
+  end
+
+  it "doesn't flag violation when using class_methods" do
+    expect_no_offenses(<<~RUBY)
+      module Foo
+        extend ActiveSupport::Concern
+
+        class_methods do
+          def a_class_method
+          end
+        end
+      end
+    RUBY
+  end
+
+  it "doesn't flag violation when module is not extending ActiveSupport::Concern" do
+    expect_no_offenses(<<~RUBY)
+      module Foo
+        module ClassMethods
+          def a_class_method
+          end
+        end
+      end
+    RUBY
+  end
+
+  it "doesn't flag violation when ClassMethods is used inside a class" do
+    expect_no_offenses(<<~RUBY)
+      class Foo
+        module ClassMethods
+          def a_class_method
+          end
+        end
+      end
+    RUBY
+  end
+
+  it "doesn't flag violation when not using either class_methods or ClassMethods" do
+    expect_no_offenses(<<~RUBY)
+      module Foo
+        extend ActiveSupport::Concern
+
+        def a_method
+        end
+      end
+    RUBY
+  end
+
+  it 'autocorrects ClassMethods into class_methods' do
+    source = <<~RUBY
+      module Foo
+        extend ActiveSupport::Concern
+
+        module ClassMethods
+          def a_class_method
+          end
+        end
+      end
+    RUBY
+    autocorrected = autocorrect_source(source)
+
+    expected_source = <<~RUBY
+      module Foo
+        extend ActiveSupport::Concern
+
+        class_methods do
+          def a_class_method
+          end
+        end
+      end
+    RUBY
+    expect(autocorrected).to eq(expected_source)
+  end
+end