Allow simple ivar ||= form. Update accordingly

app/controllers/concerns/boards_responses.rb

@@ -1,4 +1,3 @@
-# rubocop:disable Cop/ModuleWithInstanceVariables
 module BoardsResponses
   def authorize_read_list
     authorize_action_for!(board.parent, :read_list)
@@ -24,10 +23,12 @@ module BoardsResponses
     return render_403 unless can?(current_user, ability, resource)
   end
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def respond_with_boards
     respond_with(@boards)
   end
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def respond_with_board
     respond_with(@board)
   end

app/controllers/concerns/creates_commit.rb

@@ -1,7 +1,7 @@
-# rubocop:disable Cop/ModuleWithInstanceVariables
 module CreatesCommit
   extend ActiveSupport::Concern
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def create_commit(service, success_path:, failure_path:, failure_view: nil, success_notice: nil)
     if can?(current_user, :push_code, @project)
       @project_to_commit_into = @project
@@ -78,6 +78,7 @@ module CreatesCommit
     end
   end
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def new_merge_request_path
     project_new_merge_request_path(
       @project_to_commit_into,
@@ -94,6 +95,7 @@ module CreatesCommit
     project_merge_request_path(@project, @merge_request)
   end
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def merge_request_exists?
     return @merge_request if defined?(@merge_request)
 
@@ -101,10 +103,12 @@ module CreatesCommit
       .find_by(source_project_id: @project_to_commit_into, source_branch: @branch_name, target_branch: @start_branch)
   end
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def different_project?
     @project_to_commit_into != @project
   end
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def create_merge_request?
     # Even if the field is set, if we're checking the same branch
     # as the target branch in the same project,

app/controllers/concerns/cycle_analytics_params.rb

@@ -1,7 +1,6 @@
 module CycleAnalyticsParams
   extend ActiveSupport::Concern
 
-  # rubocop:disable Cop/ModuleWithInstanceVariables
   def options(params)
     @options ||= { from: start_date(params), current_user: current_user }
   end

app/controllers/concerns/issuable_actions.rb

@@ -1,4 +1,3 @@
-# rubocop:disable Cop/ModuleWithInstanceVariables
 module IssuableActions
   extend ActiveSupport::Concern
 
@@ -8,6 +7,7 @@ module IssuableActions
     before_action :authorize_admin_issuable!, only: :bulk_update
   end
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def destroy
     issuable.destroy
     destroy_method = "destroy_#{issuable.class.name.underscore}".to_sym
@@ -36,6 +36,7 @@ module IssuableActions
 
   private
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def render_conflict_response
     respond_to do |format|
       format.html do
@@ -53,6 +54,7 @@ module IssuableActions
     end
   end
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def labels
     @labels ||= LabelsFinder.new(current_user, project_id: @project.id).execute
   end
@@ -63,6 +65,7 @@ module IssuableActions
     end
   end
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def authorize_admin_issuable!
     unless can?(current_user, :"admin_#{resource_name}", @project)
       return access_denied!

app/controllers/concerns/issuable_collections.rb

@@ -1,4 +1,3 @@
-# rubocop:disable Cop/ModuleWithInstanceVariables
 module IssuableCollections
   extend ActiveSupport::Concern
   include SortingHelper
@@ -11,6 +10,7 @@ module IssuableCollections
 
   private
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def set_issues_index
     @collection_type    = "Issue"
     @issues             = issues_collection
@@ -85,6 +85,7 @@ module IssuableCollections
     finder_class.new(current_user, filter_params)
   end
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def filter_params
     set_sort_order_from_cookie
     set_default_state

app/controllers/concerns/issues_action.rb

@@ -1,8 +1,8 @@
-# rubocop:disable Cop/ModuleWithInstanceVariables
 module IssuesAction
   extend ActiveSupport::Concern
   include IssuableCollections
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def issues
     @label = issues_finder.labels.first
 

app/controllers/concerns/lfs_request.rb

@@ -90,7 +90,6 @@ module LfsRequest
     has_authentication_ability?(:build_download_code) && can?(user, :build_download_code, project)
   end
 
-  # rubocop:disable Cop/ModuleWithInstanceVariables
   def storage_project
     @storage_project ||= begin
       result = project
@@ -104,7 +103,6 @@ module LfsRequest
     end
   end
 
-  # rubocop:disable Cop/ModuleWithInstanceVariables
   def objects
     @objects ||= (params[:objects] || []).to_a
   end

app/controllers/concerns/membership_actions.rb

@@ -76,7 +76,6 @@ module MembershipActions
     end
   end
 
-  # rubocop:disable Cop/ModuleWithInstanceVariables
   def source_type
     @source_type ||= membershipable.class.to_s.humanize(capitalize: false)
   end

app/controllers/concerns/merge_requests_action.rb

@@ -1,8 +1,8 @@
-# rubocop:disable Cop/ModuleWithInstanceVariables
 module MergeRequestsAction
   extend ActiveSupport::Concern
   include IssuableCollections
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def merge_requests
     @label = merge_requests_finder.labels.first
 

app/controllers/concerns/oauth_applications.rb

@@ -13,8 +13,7 @@ module OauthApplications
     end
   end
 
-  # rubocop:disable Cop/ModuleWithInstanceVariables
   def load_scopes
-    @scopes = Doorkeeper.configuration.scopes
+    @scopes ||= Doorkeeper.configuration.scopes
   end
 end

app/controllers/concerns/requires_whitelisted_monitoring_client.rb

@@ -17,7 +17,6 @@ module RequiresWhitelistedMonitoringClient
     ip_whitelist.any? { |e| e.include?(Gitlab::RequestContext.client_ip) }
   end
 
-  # rubocop:disable Cop/ModuleWithInstanceVariables
   def ip_whitelist
     @ip_whitelist ||= Settings.monitoring.ip_whitelist.map(&IPAddr.method(:new))
   end

app/models/concerns/ignorable_column.rb

@@ -17,7 +17,6 @@ module IgnorableColumn
       super.reject { |column| ignored_columns.include?(column.name) }
     end
 
-    # rubocop:disable Cop/ModuleWithInstanceVariables
     def ignored_columns
       @ignored_columns ||= Set.new
     end

app/models/concerns/mentionable.rb

@@ -5,7 +5,6 @@
 #
 # Used by Issue, Note, MergeRequest, and Commit.
 #
-# # rubocop:disable Cop/ModuleWithInstanceVariables
 module Mentionable
   extend ActiveSupport::Concern
 
@@ -44,6 +43,7 @@ module Mentionable
     self
   end
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def all_references(current_user = nil, extractor: nil)
     @extractors ||= {}
 

app/models/concerns/noteable.rb

@@ -12,7 +12,6 @@ module Noteable
   #
   #   noteable.class           # => MergeRequest
   #   noteable.human_class_name # => "merge request"
-  # rubocop:disable Cop/ModuleWithInstanceVariables
   def human_class_name
     @human_class_name ||= base_class_name.titleize.downcase
   end
@@ -35,7 +34,6 @@ module Noteable
 
   delegate :find_discussion, to: :discussion_notes
 
-  # rubocop:disable Cop/ModuleWithInstanceVariables
   def discussions
     @discussions ||= discussion_notes
       .inc_relations_for_view
@@ -70,7 +68,6 @@ module Noteable
     discussions_resolvable? && !discussions_resolved?
   end
 
-  # rubocop:disable Cop/ModuleWithInstanceVariables
   def discussions_to_be_resolved
     @discussions_to_be_resolved ||= resolvable_discussions.select(&:to_be_resolved?)
   end

app/models/concerns/participable.rb

@@ -55,17 +55,18 @@ module Participable
   # This method processes attributes of objects in breadth-first order.
   #
   # Returns an Array of User instances.
-  # rubocop:disable Cop/ModuleWithInstanceVariables
   def participants(current_user = nil)
-    @participants ||= Hash.new do |hash, user|
-      hash[user] = raw_participants(user)
-    end
-
-    @participants[current_user]
+    all_participants[current_user]
   end
 
   private
 
+  def all_participants
+    @all_participants ||= Hash.new do |hash, user|
+      hash[user] = raw_participants(user)
+    end
+  end
+
   def raw_participants(current_user = nil)
     current_user ||= author
     ext = Gitlab::ReferenceExtractor.new(project, current_user)

app/models/concerns/protected_ref.rb

@@ -55,7 +55,6 @@ module ProtectedRef
 
   private
 
-  # rubocop:disable Cop/ModuleWithInstanceVariables
   def ref_matcher
     @ref_matcher ||= ProtectedRefMatcher.new(self)
   end

app/models/concerns/relative_positioning.rb

@@ -1,4 +1,3 @@
-# rubocop:disable Cop/ModuleWithInstanceVariables
 module RelativePositioning
   extend ActiveSupport::Concern
 
@@ -45,6 +44,7 @@ module RelativePositioning
     next_pos
   end
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def move_between(before, after)
     return move_after(before) unless after
     return move_before(after) unless before
@@ -59,6 +59,7 @@ module RelativePositioning
     self.relative_position = position_between(before.relative_position, after.relative_position)
   end
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def move_after(before = self)
     pos_before = before.relative_position
     pos_after = before.next_relative_position
@@ -74,6 +75,7 @@ module RelativePositioning
     self.relative_position = position_between(pos_before, pos_after)
   end
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def move_before(after = self)
     pos_after = after.relative_position
     pos_before = after.prev_relative_position
@@ -133,6 +135,7 @@ module RelativePositioning
     end
   end
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def save_positionable_neighbours
     return unless @positionable_neighbours
 

app/models/concerns/resolvable_discussion.rb

@@ -1,4 +1,3 @@
-# rubocop:disable Cop/ModuleWithInstanceVariables
 module ResolvableDiscussion
   extend ActiveSupport::Concern
 
@@ -31,12 +30,14 @@ module ResolvableDiscussion
               allow_nil: true
   end
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def resolvable?
     return @resolvable if @resolvable.present?
 
     @resolvable = potentially_resolvable? && notes.any?(&:resolvable?)
   end
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def resolved?
     return @resolved if @resolved.present?
 
@@ -47,12 +48,14 @@ module ResolvableDiscussion
     @first_note ||= notes.first
   end
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def first_note_to_resolve
     return unless resolvable?
 
     @first_note_to_resolve ||= notes.find(&:to_be_resolved?)
   end
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def last_resolved_note
     return unless resolved?
 
@@ -89,6 +92,7 @@ module ResolvableDiscussion
 
   private
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def update
     # Do not select `Note.resolvable`, so that system notes remain in the collection
     notes_relation = Note.where(id: notes.map(&:id))

app/models/concerns/routable.rb

@@ -1,6 +1,5 @@
 # Store object full path in separate table for easy lookup and uniq validation
 # Object must have name and path db fields and respond to parent and parent_changed? methods.
-# rubocop:disable Cop/ModuleWithInstanceVariables
 module Routable
   extend ActiveSupport::Concern
 
@@ -87,6 +86,7 @@ module Routable
     end
   end
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def full_name
     if route && route.name.present?
       @full_name ||= route.name
@@ -107,6 +107,7 @@ module Routable
     RequestStore[full_path_key] ||= uncached_full_path
   end
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def expires_full_path_cache
     RequestStore.delete(full_path_key) if RequestStore.active?
     @full_path = nil
@@ -122,6 +123,7 @@ module Routable
 
   private
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def uncached_full_path
     if route && route.path.present?
       @full_path ||= route.path
@@ -157,6 +159,7 @@ module Routable
     route.save
   end
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def prepare_route
     route || build_route(source: self)
     route.path = build_full_path

app/models/concerns/storage/legacy_namespace.rb

@@ -49,7 +49,6 @@ module Storage
 
     private
 
-    # rubocop:disable Cop/ModuleWithInstanceVariables
     def old_repository_storage_paths
       @old_repository_storage_paths ||= repository_storage_paths
     end

app/models/concerns/strip_attribute.rb

@@ -17,7 +17,6 @@ module StripAttribute
       strip_attrs.concat(attrs)
     end
 
-    # rubocop:disable Cop/ModuleWithInstanceVariables
     def strip_attrs
       @strip_attrs ||= []
     end

app/models/concerns/taskable.rb

@@ -6,7 +6,6 @@ require 'task_list/filter'
 # bugs".
 #
 # Used by MergeRequest and Issue
-# rubocop:disable Cop/ModuleWithInstanceVariables
 module Taskable
   COMPLETED    = 'completed'.freeze
   INCOMPLETE   = 'incomplete'.freeze
@@ -37,6 +36,7 @@ module Taskable
   end
 
   # Called by `TaskList::Summary`
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def task_list_items
     return [] if description.blank?
 

app/models/concerns/time_trackable.rb

@@ -4,7 +4,6 @@
 #
 # Used by Issue and MergeRequest.
 #
-# rubocop:disable Cop/ModuleWithInstanceVariables
 module TimeTrackable
   extend ActiveSupport::Concern
 
@@ -21,6 +20,7 @@ module TimeTrackable
     has_many :timelogs, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
   end
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def spend_time(options)
     @time_spent = options[:duration]
     @time_spent_user = options[:user]
@@ -50,6 +50,7 @@ module TimeTrackable
 
   private
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def reset_spent_time
     timelogs.new(time_spent: total_time_spent * -1, user: @time_spent_user)
   end
@@ -58,6 +59,7 @@ module TimeTrackable
     timelogs.new(time_spent: time_spent, user: @time_spent_user)
   end
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def check_negative_time_spent
     return if time_spent.nil? || time_spent == :reset
 

app/services/spam_check_service.rb

@@ -6,8 +6,8 @@
 # Dependencies:
 # - params with :request
 #
-# rubocop:disable Cop/ModuleWithInstanceVariables
 module SpamCheckService
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def filter_spam_check_params
     @request            = params.delete(:request)
     @api                = params.delete(:api)
@@ -18,6 +18,7 @@ module SpamCheckService
   # In order to be proceed to the spam check process, @spammable has to be
   # a dirty instance, which means it should be already assigned with the new
   # attribute values.
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def spam_check(spammable, user)
     spam_service = SpamService.new(spammable, @request)
 

app/services/system_note_service.rb

@@ -662,7 +662,6 @@ module SystemNoteService
     Rack::Utils.escape_html(text)
   end
 
-  # rubocop:disable Cop/ModuleWithInstanceVariables
   def url_helpers
     @url_helpers ||= Gitlab::Routing.url_helpers
   end

config/initializers/rugged_use_gitlab_git_attributes.rb

@@ -11,10 +11,10 @@
 # anyway, and there is no great efficiency gain from just fetching the listed
 # attributes with our implementation, so we ignore the additional arguments.
 #
-# rubocop:disable Cop/ModuleWithInstanceVariables
 module Rugged
   class Repository
     module UseGitlabGitAttributes
+      # rubocop:disable Cop/ModuleWithInstanceVariables
       def fetch_attributes(name, *)
         @attributes ||= Gitlab::Git::Attributes.new(path)
         @attributes.attributes(name)

doc/development/module_with_instance_variables.md

@@ -1,4 +1,4 @@
-## Usually modules with instance variables considered harmful
+## Modules with instance variables could be considered harmful
 
 ### Background
 
@@ -43,7 +43,7 @@ instance variables in the final giant object, and that's where the problem is.
 ### Solutions
 
 We should split the giant object into multiple objects, and they communicate
-each other with the API, i.e. public methods. In short, composition over
+with each other with the API, i.e. public methods. In short, composition over
 inheritance. This way, each smaller objects would have their own respective
 limited states, i.e. instance variables. If one instance variable goes wrong,
 we would be very clear that it's from that single small object, because
@@ -53,36 +53,67 @@ With clearly defined API, this would make things less coupled and much easier
 to debug and track, and much more extensible for other objects to use, because
 they communicate in a clear way, rather than implicit dependencies.
 
-### Exceptions
+### Acceptable use
 
 However, it's not all that bad when using instance variables in a module,
 as long as it's contained in the same module, that is no other modules or
 objects are touching them. If that's the case, then it would be an acceptable
-use. Unfortunately it's a bit hard to code this principle in the cop, so
-for now we rely on people turning off the cops, if they think that the use
-conform this rule.
+use.
 
-Here's an acceptable case:
+We especially allow the case where a single instance variable is used with
+`||=` to setup the value. This would look like:
 
 ``` ruby
-# This is ok, as long as `@attributes` is never used anywhere else.
-# Consider adding some prefix or suffix to avoid name conflicts though.
-# rubocop:disable Cop/ModuleWithInstanceVariables
-module Rugged
-  class Repository
-    module UseGitlabGitAttributes
-      def fetch_attributes(name, *)
-        @attributes ||= Gitlab::Git::Attributes.new(path)
-        @attributes.attributes(name)
-      end
-    end
-
-    prepend UseGitlabGitAttributes
+module M
+  def f
+    @f ||= true
   end
 end
 ```
 
-Here's a bad example which we should rewrite:
+Unfortunately it's not easy to code more complex rules into the cop, so
+we rely on people's best judge. If we could find another good pattern we
+could easily add to the cop, we should do it.
+
+### How to rewrite and avoid disabling this cop
+
+Even if we could just disable the cop, we should avoid doing so. Some code
+could be easily rewritten in simple form. Here's an example. Consider this
+acceptable method:
+
+``` ruby
+module Gitlab
+  module Emoji
+    def emoji_unicode_version(name)
+      @emoji_unicode_versions_by_name ||=
+        JSON.parse(File.read(Rails.root.join('fixtures', 'emojis', 'emoji-unicode-version-map.json')))
+      @emoji_unicode_versions_by_name[name]
+    end
+  end
+end
+```
+
+It's still offending because it's not just `||=`, but We could split this
+method into two:
+
+``` ruby
+module Gitlab
+  module Emoji
+    def emoji_unicode_version(name)
+      emoji_unicode_versions_by_name[name]
+    end
+
+    private
+
+    def emoji_unicode_versions_by_name
+      @emoji_unicode_versions_by_name ||=
+        JSON.parse(File.read(Rails.root.join('fixtures', 'emojis', 'emoji-unicode-version-map.json')))
+    end
+  end
+end
+```
+
+Now the cop won't complain. Here's another bad example which we could rewrite:
 
 ``` ruby
 module SpamCheckService
@@ -146,7 +177,7 @@ end
 This way, all those instance variables are isolated in `SpamCheckService`
 rather than who ever include the module, and those modules which were also
 included, making it much easier to track down the issues if there's any,
-and it also reduce the chance of having name conflicts.
+and it also reduces the chance of having name conflicts.
 
 ### Things we might need to ignore right now
 

lib/after_commit_queue.rb

@@ -20,7 +20,6 @@ module AfterCommitQueue
     end
   end
 
-  # rubocop:disable Cop/ModuleWithInstanceVariables
   def _after_commit_queue
     @after_commit_queue ||= []
   end

lib/api/api_guard.rb

@@ -2,7 +2,6 @@
 
 require 'rack/oauth2'
 
-# rubocop:disable Cop/ModuleWithInstanceVariables
 module API
   module APIGuard
     extend ActiveSupport::Concern
@@ -43,6 +42,8 @@ module API
 
     # Helper Methods for Grape Endpoint
     module HelperMethods
+      attr_reader :current_user
+
       # Invokes the doorkeeper guard.
       #
       # If token is presented and valid, then it sets @current_user.
@@ -61,6 +62,7 @@ module API
       #   scopes: (optional) scopes required for this guard.
       #           Defaults to empty array.
       #
+      # rubocop:disable Cop/ModuleWithInstanceVariables
       def doorkeeper_guard(scopes: [])
         access_token = find_access_token
         return nil unless access_token
@@ -88,10 +90,6 @@ module API
         find_user_by_authentication_token(token_string) || find_user_by_personal_access_token(token_string, scopes)
       end
 
-      def current_user
-        @current_user
-      end
-
       private
 
       def find_user_by_authentication_token(token_string)

lib/api/helpers.rb

@@ -1,4 +1,3 @@
-# rubocop:disable Cop/ModuleWithInstanceVariables
 module API
   module Helpers
     include Gitlab::Utils
@@ -33,6 +32,7 @@ module API
       end
     end
 
+    # rubocop:disable Cop/ModuleWithInstanceVariables
     def current_user
       return @current_user if defined?(@current_user)
 
@@ -396,6 +396,7 @@ module API
       warden.try(:authenticate) if verified_request?
     end
 
+    # rubocop:disable Cop/ModuleWithInstanceVariables
     def initial_current_user
       return @initial_current_user if defined?(@initial_current_user)
       Gitlab::Auth::UniqueIpsLimiter.limit_user! do
@@ -411,6 +412,7 @@ module API
       end
     end
 
+    # rubocop:disable Cop/ModuleWithInstanceVariables
     def sudo!
       return unless sudo_identifier
       return unless initial_current_user

lib/api/helpers/internal_helpers.rb

@@ -1,4 +1,3 @@
-# rubocop:disable Cop/ModuleWithInstanceVariables
 module API
   module Helpers
     module InternalHelpers
@@ -7,20 +6,20 @@ module API
         'git-upload-pack' => :ssh_upload_pack
       }.freeze
 
+      attr_reader :redirected_path
+
+      # rubocop:disable Cop/ModuleWithInstanceVariables
       def wiki?
         set_project unless defined?(@wiki)
         @wiki
       end
 
+      # rubocop:disable Cop/ModuleWithInstanceVariables
       def project
         set_project unless defined?(@project)
         @project
       end
 
-      def redirected_path
-        @redirected_path
-      end
-
       def ssh_authentication_abilities
         [
           :read_project,

lib/api/helpers/runner.rb

@@ -21,7 +21,6 @@ module API
         forbidden! unless current_runner
       end
 
-      # rubocop:disable Cop/ModuleWithInstanceVariables
       def current_runner
         @runner ||= ::Ci::Runner.find_by_token(params[:token].to_s)
       end

lib/extracts_path.rb

@@ -1,6 +1,5 @@
 # Module providing methods for dealing with separating a tree-ish string and a
 # file path string when combined in a request parameter
-# rubocop:disable Cop/ModuleWithInstanceVariables
 module ExtractsPath
   # Raised when given an invalid file path
   InvalidPathError = Class.new(StandardError)
@@ -38,6 +37,7 @@ module ExtractsPath
   #
   # Returns an Array where the first value is the tree-ish and the second is the
   # path
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def extract_ref(id)
     pair = ['', '']
 
@@ -105,6 +105,7 @@ module ExtractsPath
   #
   # Automatically renders `not_found!` if a valid tree path could not be
   # resolved (e.g., when a user inserts an invalid path or ref).
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def assign_ref_vars
     # assign allowed options
     allowed_options = ["filter_ref"]
@@ -133,6 +134,7 @@ module ExtractsPath
     render_404
   end
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def tree
     @tree ||= @repo.tree(@commit.id, @path)
   end
@@ -146,6 +148,7 @@ module ExtractsPath
     id
   end
 
+  # rubocop:disable Cop/ModuleWithInstanceVariables
   def ref_names
     return [] unless @project
 

lib/gitlab/ci/charts.rb

@@ -10,7 +10,6 @@ module Gitlab
             .transform_keys { |date| date.strftime(@format) }
         end
 
-        # rubocop:disable Cop/ModuleWithInstanceVariables
         def interval_step
           @interval_step ||= 1.day
         end
@@ -30,7 +29,6 @@ module Gitlab
           end
         end
 
-        # rubocop:disable Cop/ModuleWithInstanceVariables
         def interval_step
           @interval_step ||= 1.month
         end

lib/gitlab/ci/config/entry/configurable.rb

@@ -13,7 +13,6 @@ module Gitlab
         #   script: ...
         #   artifacts: ...
         #
-        # rubocop:disable Cop/ModuleWithInstanceVariables
         module Configurable
           extend ActiveSupport::Concern
 
@@ -25,6 +24,7 @@ module Gitlab
             end
           end
 
+          # rubocop:disable Cop/ModuleWithInstanceVariables
           def compose!(deps = nil)
             return unless valid?
 

lib/gitlab/ci/config/entry/validatable.rb

@@ -1,4 +1,3 @@
-# rubocop:disable Cop/ModuleWithInstanceVariables
 module Gitlab
   module Ci
     class Config
@@ -13,6 +12,7 @@ module Gitlab
             end
           end
 
+          # rubocop:disable Cop/ModuleWithInstanceVariables
           def errors
             @validator.messages + descendants.flat_map(&:errors)
           end

lib/gitlab/ci/model.rb

@@ -5,7 +5,6 @@ module Gitlab
         "ci_"
       end
 
-      # rubocop:disable Cop/ModuleWithInstanceVariables
       def model_name
         @model_name ||= ActiveModel::Name.new(self, nil, self.name.split("::").last)
       end

lib/gitlab/cycle_analytics/base_query.rb

@@ -7,11 +7,11 @@ module Gitlab
 
       private
 
-      # rubocop:disable Cop/ModuleWithInstanceVariables
       def base_query
         @base_query ||= stage_query
       end
 
+      # rubocop:disable Cop/ModuleWithInstanceVariables
       def stage_query
         query = mr_closing_issues_table.join(issue_table).on(issue_table[:id].eq(mr_closing_issues_table[:issue_id]))
           .join(issue_metrics_table).on(issue_table[:id].eq(issue_metrics_table[:issue_id]))

lib/gitlab/cycle_analytics/production_helper.rb

@@ -1,7 +1,7 @@
-# rubocop:disable Cop/ModuleWithInstanceVariables
 module Gitlab
   module CycleAnalytics
     module ProductionHelper
+      # rubocop:disable Cop/ModuleWithInstanceVariables
       def stage_query
         super.where(mr_metrics_table[:first_deployed_to_production_at].gteq(@options[:from]))
       end

lib/gitlab/email/handler/reply_processing.rb

@@ -12,7 +12,6 @@ module Gitlab
           raise NotImplementedError
         end
 
-        # rubocop:disable Cop/ModuleWithInstanceVariables
         def message
           @message ||= process_message
         end

lib/gitlab/emoji.rb

@@ -1,4 +1,3 @@
-# rubocop:disable Cop/ModuleWithInstanceVariables
 module Gitlab
   module Emoji
     extend self
@@ -32,8 +31,7 @@ module Gitlab
     end
 
     def emoji_unicode_version(name)
-      @emoji_unicode_versions_by_name ||= JSON.parse(File.read(Rails.root.join('fixtures', 'emojis', 'emoji-unicode-version-map.json')))
-      @emoji_unicode_versions_by_name[name]
+      emoji_unicode_versions_by_name[name]
     end
 
     def normalize_emoji_name(name)
@@ -57,5 +55,12 @@ module Gitlab
 
       ActionController::Base.helpers.content_tag('gl-emoji', emoji_info['moji'], title: emoji_info['description'], data: data)
     end
+
+    private
+
+    def emoji_unicode_versions_by_name
+      @emoji_unicode_versions_by_name ||=
+        JSON.parse(File.read(Rails.root.join('fixtures', 'emojis', 'emoji-unicode-version-map.json')))
+    end
   end
 end

lib/gitlab/identifier.rb

@@ -52,7 +52,6 @@ module Gitlab
       end
     end
 
-    # rubocop:disable Cop/ModuleWithInstanceVariables
     def identification_cache
       @identification_cache ||= {
         email: {},

lib/gitlab/metrics/influx_db.rb

@@ -1,4 +1,3 @@
-# rubocop:disable Cop/ModuleWithInstanceVariables
 module Gitlab
   module Metrics
     module InfluxDb
@@ -150,6 +149,7 @@ module Gitlab
 
       # When enabled this should be set before being used as the usual pattern
       # "@foo ||= bar" is _not_ thread-safe.
+      # rubocop:disable Cop/ModuleWithInstanceVariables
       def pool
         if influx_metrics_enabled?
           if @pool.nil?

lib/gitlab/metrics/prometheus.rb

@@ -1,6 +1,5 @@
 require 'prometheus/client'
 
-# rubocop:disable Cop/ModuleWithInstanceVariables
 module Gitlab
   module Metrics
     module Prometheus
@@ -14,6 +13,7 @@ module Gitlab
           ::File.writable?(multiprocess_files_dir)
       end
 
+      # rubocop:disable Cop/ModuleWithInstanceVariables
       def prometheus_metrics_enabled?
         return @prometheus_metrics_enabled if defined?(@prometheus_metrics_enabled)
 

lib/gitlab/prometheus/additional_metrics_parser.rb

@@ -26,7 +26,6 @@ module Gitlab
         load_yaml_file&.map(&:deep_symbolize_keys).freeze
       end
 
-      # rubocop:disable Cop/ModuleWithInstanceVariables
       def load_yaml_file
         @loaded_yaml_file ||= YAML.load_file(Rails.root.join('config/prometheus/additional_metrics.yml'))
       end

lib/gitlab/prometheus/queries/query_additional_metrics.rb

@@ -56,7 +56,6 @@ module Gitlab
           query
         end
 
-        # rubocop:disable Cop/ModuleWithInstanceVariables
         def available_metrics
           @available_metrics ||= client_label_values || []
         end

lib/gitlab/regex.rb

@@ -1,4 +1,3 @@
-# rubocop:disable Cop/ModuleWithInstanceVariables
 module Gitlab
   module Regex
     extend self

lib/gitlab/slash_commands/presenters/issue_base.rb

@@ -1,4 +1,3 @@
-# rubocop:disable Cop/ModuleWithInstanceVariables
 module Gitlab
   module SlashCommands
     module Presenters
@@ -11,14 +10,17 @@ module Gitlab
           issuable.open? ? 'Open' : 'Closed'
         end
 
+        # rubocop:disable Cop/ModuleWithInstanceVariables
         def project
           @resource.project
         end
 
+        # rubocop:disable Cop/ModuleWithInstanceVariables
         def author
           @resource.author
         end
 
+        # rubocop:disable Cop/ModuleWithInstanceVariables
         def fields
           [
             {

lib/gitlab/themes.rb

@@ -72,7 +72,6 @@ module Gitlab
 
     private
 
-    # rubocop:disable Cop/ModuleWithInstanceVariables
     def default_id
       @default_id ||= begin
         id = Gitlab.config.gitlab.default_theme.to_i

lib/tasks/gitlab/task_helpers.rb

@@ -1,6 +1,5 @@
 require 'rainbow/ext/string'
 
-# rubocop:disable Cop/ModuleWithInstanceVariables
 module Gitlab
   TaskFailedError = Class.new(StandardError)
   TaskAbortedByUserError = Class.new(StandardError)
@@ -105,6 +104,7 @@ module Gitlab
       Gitlab.config.gitlab.user
     end
 
+    # rubocop:disable Cop/ModuleWithInstanceVariables
     def gitlab_user?
       return @is_gitlab_user unless @is_gitlab_user.nil?
 
@@ -112,6 +112,7 @@ module Gitlab
       @is_gitlab_user = current_user == gitlab_user
     end
 
+    # rubocop:disable Cop/ModuleWithInstanceVariables
     def warn_user_is_not_gitlab
       return if @warned_user_not_gitlab
 

qa/qa/runtime/namespace.rb

@@ -3,7 +3,6 @@ module QA
     module Namespace
       extend self
 
-      # rubocop:disable Cop/ModuleWithInstanceVariables
       def time
         @time ||= Time.now
       end

rubocop/cop/module_with_instance_variables.rb

@@ -45,11 +45,29 @@ module RuboCop
 
       def check_method_definition(node)
         node.each_child_node(:def) do |definition|
-          definition.each_descendant(:ivar, :ivasgn) do |offense|
-            add_offense(offense, :expression)
+          # We allow this pattern:
+          # def f
+          #   @f ||= true
+          # end
+          if only_ivar_or_assignment?(definition)
+            # We don't allow if any other ivar is used
+            definition.each_descendant(:ivar) do |offense|
+              add_offense(offense, :expression)
+            end
+          else
+            definition.each_descendant(:ivar, :ivasgn) do |offense|
+              add_offense(offense, :expression)
+            end
           end
         end
       end
+
+      def only_ivar_or_assignment?(definition)
+        node = definition.child_nodes.last
+
+        definition.child_nodes.size == 2 &&
+          node.or_asgn_type? && node.child_nodes.first.ivasgn_type?
+      end
     end
   end
 end

spec/rubocop/cop/module_with_instance_variables_spec.rb

@@ -19,12 +19,20 @@ describe RuboCop::Cop::ModuleWithInstanceVariables do
     end
   end
 
+  shared_examples('not registering offense') do
+    it 'does not register offenses' do
+      inspect_source(cop, source)
+
+      expect(cop.offenses).to be_empty
+    end
+  end
+
   context 'when source is a regular module' do
     let(:source) do
       <<~RUBY
         module M
           def f
-            @f ||= true
+            @f = true
           end
         end
       RUBY
@@ -59,7 +67,7 @@ describe RuboCop::Cop::ModuleWithInstanceVariables do
         module N
           module M
             def f
-              @f ||= true
+              @f = true
             end
 
             def g
@@ -79,39 +87,86 @@ describe RuboCop::Cop::ModuleWithInstanceVariables do
     it_behaves_like 'registering offense'
   end
 
-  context 'when source is offending but it is a rails helper' do
-    before do
-      allow(cop).to receive(:rails_helper?).and_return(true)
-    end
-
-    it 'does not register offenses' do
-      inspect_source(cop, <<~RUBY)
-        module M
-          def f
-            @f ||= true
-          end
-        end
-      RUBY
-
-      expect(cop.offenses).to be_empty
-    end
-  end
-
-  context 'when source is offending but it is a rails mailer' do
-    before do
-      allow(cop).to receive(:rails_mailer?).and_return(true)
-    end
-
-    it 'does not register offenses' do
-      inspect_source(cop, <<~RUBY)
+  context 'with regular ivar assignment' do
+    let(:source) do
+      <<~RUBY
         module M
           def f
             @f = true
           end
         end
       RUBY
+    end
 
-      expect(cop.offenses).to be_empty
+    context 'when source is offending but it is a rails helper' do
+      before do
+        allow(cop).to receive(:rails_helper?).and_return(true)
+      end
+
+      it_behaves_like 'not registering offense'
+    end
+
+    context 'when source is offending but it is a rails mailer' do
+      before do
+        allow(cop).to receive(:rails_mailer?).and_return(true)
+      end
+
+      it_behaves_like 'not registering offense'
+    end
+
+    context 'when source is offending but it is a spec helper' do
+      before do
+        allow(cop).to receive(:spec_helper?).and_return(true)
+      end
+
+      it_behaves_like 'not registering offense'
     end
   end
+
+  context 'when source is using simple or ivar assignment' do
+    let(:source) do
+      <<~RUBY
+        module M
+          def f
+            @f ||= true
+          end
+        end
+      RUBY
+    end
+
+    it_behaves_like 'not registering offense'
+  end
+
+  context 'when source is using simple or ivar assignment with other ivar' do
+    let(:source) do
+      <<~RUBY
+        module M
+          def f
+            @f ||= g(@g)
+          end
+        end
+      RUBY
+    end
+
+    let(:offending_lines) { [3] }
+
+    it_behaves_like 'registering offense'
+  end
+
+  context 'when source is using or ivar assignment with something else' do
+    let(:source) do
+      <<~RUBY
+        module M
+          def f
+            @f ||= true
+            @f.to_s
+          end
+        end
+      RUBY
+    end
+
+    let(:offending_lines) { [3, 4] }
+
+    it_behaves_like 'registering offense'
+  end
 end