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

29 files changed, 202 insertions, 25 deletions

diff --git a/app/models/concerns/atomic_internal_id.rb b/app/models/concerns/atomic_internal_id.rb
index 7f6d48d972c..4e15b60ccd1 100644
--- a/app/models/concerns/atomic_internal_id.rb
+++ b/app/models/concerns/atomic_internal_id.rb
@@ -26,7 +26,7 @@
 module AtomicInternalId
   extend ActiveSupport::Concern
 
-  module ClassMethods
+  class_methods do
     def has_internal_id(column, scope:, init:, presence: true) # rubocop:disable Naming/PredicateName
       # We require init here to retain the ability to recalculate in the absence of a
       # InternaLId record (we may delete records in `internal_ids` for example).
diff --git a/app/models/concerns/awardable.rb b/app/models/concerns/awardable.rb
index 4200253053a..6f29c92d176 100644
--- a/app/models/concerns/awardable.rb
+++ b/app/models/concerns/awardable.rb
@@ -12,7 +12,7 @@ module Awardable
     end
   end
 
-  module ClassMethods
+  class_methods do
     def awarded(user, name)
       sql = <<~EOL
         EXISTS (
diff --git a/app/models/concerns/case_sensitivity.rb b/app/models/concerns/case_sensitivity.rb
index 0ba542b75ab..6e80365ee5b 100644
--- a/app/models/concerns/case_sensitivity.rb
+++ b/app/models/concerns/case_sensitivity.rb
@@ -4,7 +4,7 @@
 module CaseSensitivity
   extend ActiveSupport::Concern
 
-  module ClassMethods
+  class_methods do
     # Queries the given columns regardless of the casing used.
     #
     # Unlike other ActiveRecord methods this method only operates on a Hash.
diff --git a/app/models/concerns/each_batch.rb b/app/models/concerns/each_batch.rb
index a9e14cb55eb..8cf0b8b154d 100644
--- a/app/models/concerns/each_batch.rb
+++ b/app/models/concerns/each_batch.rb
@@ -3,7 +3,7 @@
 module EachBatch
   extend ActiveSupport::Concern
 
-  module ClassMethods
+  class_methods do
     # Iterates over the rows in a relation in batches, similar to Rails'
     # `in_batches` but in a more efficient way.
     #
diff --git a/app/models/concerns/ignorable_column.rb b/app/models/concerns/ignorable_column.rb
index 2b074c1921c..5c1f7dfcd2a 100644
--- a/app/models/concerns/ignorable_column.rb
+++ b/app/models/concerns/ignorable_column.rb
@@ -14,7 +14,7 @@
 module IgnorableColumn
   extend ActiveSupport::Concern
 
-  module ClassMethods
+  class_methods do
     def columns
       super.reject { |column| ignored_columns.include?(column.name) }
     end
diff --git a/app/models/concerns/issuable.rb b/app/models/concerns/issuable.rb
index e8072145551..f881ce2321c 100644
--- a/app/models/concerns/issuable.rb
+++ b/app/models/concerns/issuable.rb
@@ -118,7 +118,7 @@ module Issuable
     end
   end
 
-  module ClassMethods
+  class_methods do
     # Searches for records with a matching title.
     #
     # This method uses ILIKE on PostgreSQL and LIKE on MySQL.
diff --git a/app/models/concerns/loaded_in_group_list.rb b/app/models/concerns/loaded_in_group_list.rb
index a2233eb2997..fc15c6d55ed 100644
--- a/app/models/concerns/loaded_in_group_list.rb
+++ b/app/models/concerns/loaded_in_group_list.rb
@@ -3,7 +3,7 @@
 module LoadedInGroupList
   extend ActiveSupport::Concern
 
-  module ClassMethods
+  class_methods do
     def with_counts(archived:)
       selects_including_counts = [
         'namespaces.*',
diff --git a/app/models/concerns/manual_inverse_association.rb b/app/models/concerns/manual_inverse_association.rb
index d0d781dc15f..e18edd33ba7 100644
--- a/app/models/concerns/manual_inverse_association.rb
+++ b/app/models/concerns/manual_inverse_association.rb
@@ -3,7 +3,7 @@
 module ManualInverseAssociation
   extend ActiveSupport::Concern
 
-  module ClassMethods
+  class_methods do
     def manual_inverse_association(association, inverse)
       define_method(association) do |*args|
         super(*args).tap do |value|
diff --git a/app/models/concerns/mentionable.rb b/app/models/concerns/mentionable.rb
index 7e7eccb1c27..393607e82c4 100644
--- a/app/models/concerns/mentionable.rb
+++ b/app/models/concerns/mentionable.rb
@@ -10,7 +10,7 @@
 module Mentionable
   extend ActiveSupport::Concern
 
-  module ClassMethods
+  class_methods do
     # Indicate which attributes of the Mentionable to search for GFM references.
     def attr_mentionable(attr, options = {})
       attr = attr.to_s
diff --git a/app/models/concerns/optionally_search.rb b/app/models/concerns/optionally_search.rb
index dec97b7dee8..4093429e372 100644
--- a/app/models/concerns/optionally_search.rb
+++ b/app/models/concerns/optionally_search.rb
@@ -3,7 +3,7 @@
 module OptionallySearch
   extend ActiveSupport::Concern
 
-  module ClassMethods
+  class_methods do
     def search(*)
       raise(
         NotImplementedError,
diff --git a/app/models/concerns/participable.rb b/app/models/concerns/participable.rb
index 1f6c42f3b3a..614c3242874 100644
--- a/app/models/concerns/participable.rb
+++ b/app/models/concerns/participable.rb
@@ -26,7 +26,7 @@
 module Participable
   extend ActiveSupport::Concern
 
-  module ClassMethods
+  class_methods do
     # Adds a list of participant attributes. Attributes can either be symbols or
     # Procs.
     #
diff --git a/app/models/concerns/referable.rb b/app/models/concerns/referable.rb
index 468eaf68883..58143a32fdc 100644
--- a/app/models/concerns/referable.rb
+++ b/app/models/concerns/referable.rb
@@ -40,7 +40,7 @@ module Referable
     end
   end
 
-  module ClassMethods
+  class_methods do
     # The character that prefixes the actual reference identifier
     #
     # This should be overridden by the including class.
diff --git a/app/models/concerns/resolvable_note.rb b/app/models/concerns/resolvable_note.rb
index f47e20229f1..16ea330701d 100644
--- a/app/models/concerns/resolvable_note.rb
+++ b/app/models/concerns/resolvable_note.rb
@@ -20,7 +20,7 @@ module ResolvableNote
     scope :unresolved, -> { resolvable.where(resolved_at: nil) }
   end
 
-  module ClassMethods
+  class_methods do
     # This method must be kept in sync with `#resolve!`
     def resolve!(current_user)
       unresolved.update_all(resolved_at: Time.now, resolved_by_id: current_user.id)
diff --git a/app/models/concerns/select_for_project_authorization.rb b/app/models/concerns/select_for_project_authorization.rb
index 39306179eb8..333c9118aa5 100644
--- a/app/models/concerns/select_for_project_authorization.rb
+++ b/app/models/concerns/select_for_project_authorization.rb
@@ -3,7 +3,7 @@
 module SelectForProjectAuthorization
   extend ActiveSupport::Concern
 
-  module ClassMethods
+  class_methods do
     def select_for_project_authorization
       select("projects.id AS project_id, members.access_level")
     end
diff --git a/app/models/concerns/sha_attribute.rb b/app/models/concerns/sha_attribute.rb
index c322c356db2..e51b4e22c96 100644
--- a/app/models/concerns/sha_attribute.rb
+++ b/app/models/concerns/sha_attribute.rb
@@ -3,7 +3,7 @@
 module ShaAttribute
   extend ActiveSupport::Concern
 
-  module ClassMethods
+  class_methods do
     def sha_attribute(name)
       return if ENV['STATIC_VERIFICATION']
 
diff --git a/app/models/concerns/sortable.rb b/app/models/concerns/sortable.rb
index 501bd1bb83c..29e48f0c5f7 100644
--- a/app/models/concerns/sortable.rb
+++ b/app/models/concerns/sortable.rb
@@ -19,7 +19,7 @@ module Sortable
     scope :order_name_desc, -> { reorder(Arel::Nodes::Descending.new(arel_table[:name].lower)) }
   end
 
-  module ClassMethods
+  class_methods do
     def order_by(method)
       case method.to_s
       when 'created_asc'  then order_created_asc
diff --git a/app/models/concerns/spammable.rb b/app/models/concerns/spammable.rb
index c6e3dc385fe..3ff4b4046d3 100644
--- a/app/models/concerns/spammable.rb
+++ b/app/models/concerns/spammable.rb
@@ -3,7 +3,7 @@
 module Spammable
   extend ActiveSupport::Concern
 
-  module ClassMethods
+  class_methods do
     def attr_spammable(attr, options = {})
       spammable_attrs << [attr.to_s, options]
     end
diff --git a/app/models/concerns/strip_attribute.rb b/app/models/concerns/strip_attribute.rb
index 344f677a3f3..c9f5ba7793d 100644
--- a/app/models/concerns/strip_attribute.rb
+++ b/app/models/concerns/strip_attribute.rb
@@ -14,7 +14,7 @@
 module StripAttribute
   extend ActiveSupport::Concern
 
-  module ClassMethods
+  class_methods do
     def strip_attributes(*attrs)
       strip_attrs.concat(attrs)
     end
diff --git a/app/workers/concerns/application_worker.rb b/app/workers/concerns/application_worker.rb
index bb06e31641d..d64c2f82a09 100644
--- a/app/workers/concerns/application_worker.rb
+++ b/app/workers/concerns/application_worker.rb
@@ -11,7 +11,7 @@ module ApplicationWorker
     set_queue
   end
 
-  module ClassMethods
+  class_methods do
     def inherited(subclass)
       subclass.set_queue
     end
diff --git a/app/workers/concerns/waitable_worker.rb b/app/workers/concerns/waitable_worker.rb
index d85bc7d1660..27b94a82444 100644
--- a/app/workers/concerns/waitable_worker.rb
+++ b/app/workers/concerns/waitable_worker.rb
@@ -3,7 +3,7 @@
 module WaitableWorker
   extend ActiveSupport::Concern
 
-  module ClassMethods
+  class_methods do
     # Schedules multiple jobs and waits for them to be completed.
     def bulk_perform_and_wait(args_list, timeout: 10)
       # Short-circuit: it's more efficient to do small numbers of jobs inline
diff --git a/changelogs/unreleased/50414-rubocop-rule-to-enforce-class-methods-over-module.yml b/changelogs/unreleased/50414-rubocop-rule-to-enforce-class-methods-over-module.yml
new file mode 100644
index 00000000000..1694fb2376d
--- /dev/null
+++ b/changelogs/unreleased/50414-rubocop-rule-to-enforce-class-methods-over-module.yml
@@ -0,0 +1,5 @@
+---
+title: Adds Rubocop rule to enforce class_methods over module ClassMethods
+merge_request: 21379
+author: Jacopo Beschi @jacopo-beschi
+type: added
diff --git a/lib/api/api_guard.rb b/lib/api/api_guard.rb
index c17089759de..8ee7987cfff 100644
--- a/lib/api/api_guard.rb
+++ b/lib/api/api_guard.rb
@@ -84,7 +84,7 @@ module API
       end
     end
 
-    module ClassMethods
+    class_methods do
       private
 
       def install_error_responders(base)
diff --git a/lib/api/projects_relation_builder.rb b/lib/api/projects_relation_builder.rb
index 6482fd94ab8..9fd79c491c2 100644
--- a/lib/api/projects_relation_builder.rb
+++ b/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)
diff --git a/lib/gitlab/github_import/representation/expose_attribute.rb b/lib/gitlab/github_import/representation/expose_attribute.rb
index c3405759631..d2438ee8094 100644
--- a/lib/gitlab/github_import/representation/expose_attribute.rb
+++ b/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:
diff --git a/lib/gitlab/graphql/mount_mutation.rb b/lib/gitlab/graphql/mount_mutation.rb
index 8cab84d7a5f..9048967d4e1 100644
--- a/lib/gitlab/graphql/mount_mutation.rb
+++ b/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
diff --git a/lib/static_model.rb b/lib/static_model.rb
index 60e2dd82e4e..44673c2b5f6 100644
--- a/lib/static_model.rb
+++ b/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'
diff --git a/rubocop/cop/prefer_class_methods_over_module.rb b/rubocop/cop/prefer_class_methods_over_module.rb
new file mode 100644
index 00000000000..0dfa80ccfab
--- /dev/null
+++ b/rubocop/cop/prefer_class_methods_over_module.rb
@@ -0,0 +1,73 @@
+# 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
diff --git a/rubocop/rubocop.rb b/rubocop/rubocop.rb
index eaf421a7235..d823fa4edb1 100644
--- a/rubocop/rubocop.rb
+++ b/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'
diff --git a/spec/rubocop/cop/prefer_class_methods_over_module_spec.rb b/spec/rubocop/cop/prefer_class_methods_over_module_spec.rb
new file mode 100644
index 00000000000..4739f0e6c47
--- /dev/null
+++ b/spec/rubocop/cop/prefer_class_methods_over_module_spec.rb
@@ -0,0 +1,98 @@
+# 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