Merge branch 'rubocop/enable-access-modifiers-cops' into 'master'

Enable Rubocop cops that check access modifiers

## What does this MR do?

This MR enables Rubocop cops that detect methods that should be restricted but are the part of public API because of access modifiers used improperly.

This also fixes existing offenses.

## Why was this MR needed?

Some method in our codebase are public instead of being private because it is sometimes difficult to get it right without static analysis.

## What are the relevant issue numbers?

See #17478  
Closes #17372 

See merge request !5014

16 files changed, 184 insertions, 177 deletions

diff --git a/.rubocop.yml b/.rubocop.yml
index 6adbda53456..556a5d11a39 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -510,6 +510,15 @@ Metrics/PerceivedComplexity:
 
 #################### Lint ################################
 
+# Checks for useless access modifiers.
+Lint/UselessAccessModifier:
+  Enabled: true
+
+# Checks for attempts to use `private` or `protected` to set the visibility
+# of a class method, which does not work.
+Lint/IneffectiveAccessModifier:
+  Enabled: false
+
 # Checks for ambiguous operators in the first argument of a method invocation
 # without parentheses.
 Lint/AmbiguousOperator:
diff --git a/.rubocop_todo.yml b/.rubocop_todo.yml
index b622b9239d4..76ae5952753 100644
--- a/.rubocop_todo.yml
+++ b/.rubocop_todo.yml
@@ -19,10 +19,6 @@ Lint/AssignmentInCondition:
 Lint/HandleExceptions:
   Enabled: false
 
-# Offense count: 21
-Lint/IneffectiveAccessModifier:
-  Enabled: false
-
 # Offense count: 2
 Lint/Loop:
   Enabled: false
@@ -48,10 +44,6 @@ Lint/UnusedBlockArgument:
 Lint/UnusedMethodArgument:
   Enabled: false
 
-# Offense count: 11
-Lint/UselessAccessModifier:
-  Enabled: false
-
 # Offense count: 12
 # Cop supports --auto-correct.
 Performance/PushSplat:
diff --git a/app/controllers/import/bitbucket_controller.rb b/app/controllers/import/bitbucket_controller.rb
index 25e58724860..944c73d139a 100644
--- a/app/controllers/import/bitbucket_controller.rb
+++ b/app/controllers/import/bitbucket_controller.rb
@@ -82,8 +82,6 @@ class Import::BitbucketController < Import::BaseController
     go_to_bitbucket_for_permissions
   end
 
-  private
-
   def access_params
     {
       bitbucket_access_token: session[:bitbucket_access_token],
diff --git a/app/controllers/import/gitlab_controller.rb b/app/controllers/import/gitlab_controller.rb
index 23a396e8084..08130ee8176 100644
--- a/app/controllers/import/gitlab_controller.rb
+++ b/app/controllers/import/gitlab_controller.rb
@@ -61,8 +61,6 @@ class Import::GitlabController < Import::BaseController
     go_to_gitlab_for_permissions
   end
 
-  private
-
   def access_params
     { gitlab_access_token: session[:gitlab_access_token] }
   end
diff --git a/app/helpers/diff_helper.rb b/app/helpers/diff_helper.rb
index 4c031942793..f35e2f6ddcd 100644
--- a/app/helpers/diff_helper.rb
+++ b/app/helpers/diff_helper.rb
@@ -144,8 +144,6 @@ module DiffHelper
     toggle_whitespace_link(url, options)
   end
 
-  private
-
   def hide_whitespace?
     params[:w] == '1'
   end
diff --git a/app/models/concerns/token_authenticatable.rb b/app/models/concerns/token_authenticatable.rb
index 885deaf78d2..24c7b26d223 100644
--- a/app/models/concerns/token_authenticatable.rb
+++ b/app/models/concerns/token_authenticatable.rb
@@ -1,12 +1,26 @@
 module TokenAuthenticatable
   extend ActiveSupport::Concern
 
+  private
+
+  def write_new_token(token_field)
+    new_token = generate_token(token_field)
+    write_attribute(token_field, new_token)
+  end
+
+  def generate_token(token_field)
+    loop do
+      token = Devise.friendly_token
+      break token unless self.class.unscoped.find_by(token_field => token)
+    end
+  end
+
   class_methods do
     def authentication_token_fields
       @token_fields || []
     end
 
-    private
+    private # rubocop:disable Lint/UselessAccessModifier
 
     def add_authentication_token_field(token_field)
       @token_fields = [] unless @token_fields
@@ -32,18 +46,4 @@ module TokenAuthenticatable
       end
     end
   end
-
-  private
-
-  def write_new_token(token_field)
-    new_token = generate_token(token_field)
-    write_attribute(token_field, new_token)
-  end
-
-  def generate_token(token_field)
-    loop do
-      token = Devise.friendly_token
-      break token unless self.class.unscoped.find_by(token_field => token)
-    end
-  end
 end
diff --git a/app/services/auth/container_registry_authentication_service.rb b/app/services/auth/container_registry_authentication_service.rb
index e294a962352..6072123b851 100644
--- a/app/services/auth/container_registry_authentication_service.rb
+++ b/app/services/auth/container_registry_authentication_service.rb
@@ -24,10 +24,14 @@ module Auth
       token[:access] = names.map do |name|
         { type: 'repository', name: name, actions: %w(*) }
       end
-      
+
       token.encoded
     end
 
+    def self.token_expire_at
+      Time.now + current_application_settings.container_registry_token_expire_delay.minutes
+    end
+
     private
 
     def authorized_token(*accesses)
@@ -35,7 +39,7 @@ module Auth
       token.issuer = registry.issuer
       token.audience = params[:service]
       token.subject = current_user.try(:username)
-      token.expire_time = ContainerRegistryAuthenticationService.token_expire_at
+      token.expire_time = self.class.token_expire_at
       token[:access] = accesses.compact
       token
     end
@@ -81,9 +85,5 @@ module Auth
     def registry
       Gitlab.config.registry
     end
-
-    def self.token_expire_at
-      Time.now + current_application_settings.container_registry_token_expire_delay.minutes
-    end
   end
 end
diff --git a/app/services/system_note_service.rb b/app/services/system_note_service.rb
index 1ab3b5789bc..e13dc9265b8 100644
--- a/app/services/system_note_service.rb
+++ b/app/services/system_note_service.rb
@@ -2,7 +2,9 @@
 #
 # Used for creating system notes (e.g., when a user references a merge request
 # from an issue, an issue's assignee changes, an issue is closed, etc.)
-class SystemNoteService
+module SystemNoteService
+  extend self
+
   # Called when commits are added to a Merge Request
   #
   # noteable         - Noteable object
@@ -15,7 +17,7 @@ class SystemNoteService
   # See new_commit_summary and existing_commit_summary.
   #
   # Returns the created Note object
-  def self.add_commits(noteable, project, author, new_commits, existing_commits = [], oldrev = nil)
+  def add_commits(noteable, project, author, new_commits, existing_commits = [], oldrev = nil)
     total_count  = new_commits.length + existing_commits.length
     commits_text = "#{total_count} commit".pluralize(total_count)
 
@@ -40,7 +42,7 @@ class SystemNoteService
   #   "Reassigned to @rspeicher"
   #
   # Returns the created Note object
-  def self.change_assignee(noteable, project, author, assignee)
+  def change_assignee(noteable, project, author, assignee)
     body = assignee.nil? ? 'Assignee removed' : "Reassigned to #{assignee.to_reference}"
 
     create_note(noteable: noteable, project: project, author: author, note: body)
@@ -63,7 +65,7 @@ class SystemNoteService
   #   "Removed ~5 label"
   #
   # Returns the created Note object
-  def self.change_label(noteable, project, author, added_labels, removed_labels)
+  def change_label(noteable, project, author, added_labels, removed_labels)
     labels_count = added_labels.count + removed_labels.count
 
     references     = ->(label) { label.to_reference(format: :id) }
@@ -101,7 +103,7 @@ class SystemNoteService
   #   "Miletone changed to 7.11"
   #
   # Returns the created Note object
-  def self.change_milestone(noteable, project, author, milestone)
+  def change_milestone(noteable, project, author, milestone)
     body = 'Milestone '
     body += milestone.nil? ? 'removed' : "changed to #{milestone.to_reference(project)}"
 
@@ -123,7 +125,7 @@ class SystemNoteService
   #   "Status changed to closed by bc17db76"
   #
   # Returns the created Note object
-  def self.change_status(noteable, project, author, status, source)
+  def change_status(noteable, project, author, status, source)
     body = "Status changed to #{status}"
     body << " by #{source.gfm_reference(project)}" if source
 
@@ -131,26 +133,26 @@ class SystemNoteService
   end
 
   # Called when 'merge when build succeeds' is executed
-  def self.merge_when_build_succeeds(noteable, project, author, last_commit)
+  def merge_when_build_succeeds(noteable, project, author, last_commit)
     body = "Enabled an automatic merge when the build for #{last_commit.to_reference(project)} succeeds"
 
     create_note(noteable: noteable, project: project, author: author, note: body)
   end
 
   # Called when 'merge when build succeeds' is canceled
-  def self.cancel_merge_when_build_succeeds(noteable, project, author)
+  def cancel_merge_when_build_succeeds(noteable, project, author)
     body = 'Canceled the automatic merge'
 
     create_note(noteable: noteable, project: project, author: author, note: body)
   end
 
-  def self.remove_merge_request_wip(noteable, project, author)
+  def remove_merge_request_wip(noteable, project, author)
     body = 'Unmarked this merge request as a Work In Progress'
 
     create_note(noteable: noteable, project: project, author: author, note: body)
   end
 
-  def self.add_merge_request_wip(noteable, project, author)
+  def add_merge_request_wip(noteable, project, author)
     body = 'Marked this merge request as a **Work In Progress**'
 
     create_note(noteable: noteable, project: project, author: author, note: body)
@@ -168,7 +170,7 @@ class SystemNoteService
   #   "Title changed from **Old** to **New**"
   #
   # Returns the created Note object
-  def self.change_title(noteable, project, author, old_title)
+  def change_title(noteable, project, author, old_title)
     new_title = noteable.title.dup
 
     old_diffs, new_diffs = Gitlab::Diff::InlineDiff.new(old_title, new_title).inline_diffs
@@ -191,7 +193,7 @@ class SystemNoteService
   # "Made the issue confidential"
   #
   # Returns the created Note object
-  def self.change_issue_confidentiality(issue, project, author)
+  def change_issue_confidentiality(issue, project, author)
     body = issue.confidential ? 'Made the issue confidential' : 'Made the issue visible'
     create_note(noteable: issue, project: project, author: author, note: body)
   end
@@ -210,7 +212,7 @@ class SystemNoteService
   #   "Target branch changed from `Old` to `New`"
   #
   # Returns the created Note object
-  def self.change_branch(noteable, project, author, branch_type, old_branch, new_branch)
+  def change_branch(noteable, project, author, branch_type, old_branch, new_branch)
     body = "#{branch_type} branch changed from `#{old_branch}` to `#{new_branch}`".capitalize
     create_note(noteable: noteable, project: project, author: author, note: body)
   end
@@ -229,7 +231,7 @@ class SystemNoteService
   #   "Restored target branch `feature`"
   #
   # Returns the created Note object
-  def self.change_branch_presence(noteable, project, author, branch_type, branch, presence)
+  def change_branch_presence(noteable, project, author, branch_type, branch, presence)
     verb =
       if presence == :add
         'restored'
@@ -245,7 +247,7 @@ class SystemNoteService
   # Example note text:
   #
   #   "Started branch `201-issue-branch-button`"
-  def self.new_issue_branch(issue, project, author, branch)
+  def new_issue_branch(issue, project, author, branch)
     h = Gitlab::Routing.url_helpers
     link = h.namespace_project_compare_url(project.namespace, project, from: project.default_branch, to: branch)
 
@@ -270,7 +272,7 @@ class SystemNoteService
   # See cross_reference_note_content.
   #
   # Returns the created Note object
-  def self.cross_reference(noteable, mentioner, author)
+  def cross_reference(noteable, mentioner, author)
     return if cross_reference_disallowed?(noteable, mentioner)
 
     gfm_reference = mentioner.gfm_reference(noteable.project)
@@ -294,7 +296,7 @@ class SystemNoteService
     end
   end
 
-  def self.cross_reference?(note_text)
+  def cross_reference?(note_text)
     note_text.start_with?(cross_reference_note_prefix)
   end
 
@@ -308,7 +310,7 @@ class SystemNoteService
   # mentioner - Mentionable object
   #
   # Returns Boolean
-  def self.cross_reference_disallowed?(noteable, mentioner)
+  def cross_reference_disallowed?(noteable, mentioner)
     return true if noteable.is_a?(ExternalIssue) && !noteable.project.jira_tracker_active?
     return false unless mentioner.is_a?(MergeRequest)
     return false unless noteable.is_a?(Commit)
@@ -328,7 +330,7 @@ class SystemNoteService
   #
   # Returns Boolean
 
-  def self.cross_reference_exists?(noteable, mentioner)
+  def cross_reference_exists?(noteable, mentioner)
     # Initial scope should be system notes of this noteable type
     notes = Note.system.where(noteable_type: noteable.class)
 
@@ -342,9 +344,60 @@ class SystemNoteService
     notes_for_mentioner(mentioner, noteable, notes).count > 0
   end
 
+  # Build an Array of lines detailing each commit added in a merge request
+  #
+  # new_commits - Array of new Commit objects
+  #
+  # Returns an Array of Strings
+  def new_commit_summary(new_commits)
+    new_commits.collect do |commit|
+      "* #{commit.short_id} - #{escape_html(commit.title)}"
+    end
+  end
+
+  # Called when the status of a Task has changed
+  #
+  # noteable  - Noteable object.
+  # project   - Project owning noteable
+  # author    - User performing the change
+  # new_task  - TaskList::Item object.
+  #
+  # Example Note text:
+  #
+  #   "Soandso marked the task Whatever as completed."
+  #
+  # Returns the created Note object
+  def change_task_status(noteable, project, author, new_task)
+    status_label = new_task.complete? ? Taskable::COMPLETED : Taskable::INCOMPLETE
+    body = "Marked the task **#{new_task.source}** as #{status_label}"
+    create_note(noteable: noteable, project: project, author: author, note: body)
+  end
+
+  # Called when noteable has been moved to another project
+  #
+  # direction    - symbol, :to or :from
+  # noteable     - Noteable object
+  # noteable_ref - Referenced noteable
+  # author       - User performing the move
+  #
+  # Example Note text:
+  #
+  #   "Moved to some_namespace/project_new#11"
+  #
+  # Returns the created Note object
+  def noteable_moved(noteable, project, noteable_ref, author, direction:)
+    unless [:to, :from].include?(direction)
+      raise ArgumentError, "Invalid direction `#{direction}`"
+    end
+
+    cross_reference = noteable_ref.to_reference(project)
+    body = "Moved #{direction} #{cross_reference}"
+    create_note(noteable: noteable, project: project, author: author, note: body)
+  end
+
   private
 
-  def self.notes_for_mentioner(mentioner, noteable, notes)
+  def notes_for_mentioner(mentioner, noteable, notes)
     if mentioner.is_a?(Commit)
       notes.where('note LIKE ?', "#{cross_reference_note_prefix}%#{mentioner.to_reference(nil)}")
     else
@@ -353,29 +406,18 @@ class SystemNoteService
     end
   end
 
-  def self.create_note(args = {})
+  def create_note(args = {})
     Note.create(args.merge(system: true))
   end
 
-  def self.cross_reference_note_prefix
+  def cross_reference_note_prefix
     'mentioned in '
   end
 
-  def self.cross_reference_note_content(gfm_reference)
+  def cross_reference_note_content(gfm_reference)
     "#{cross_reference_note_prefix}#{gfm_reference}"
   end
 
-  # Build an Array of lines detailing each commit added in a merge request
-  #
-  # new_commits - Array of new Commit objects
-  #
-  # Returns an Array of Strings
-  def self.new_commit_summary(new_commits)
-    new_commits.collect do |commit|
-      "* #{commit.short_id} - #{escape_html(commit.title)}"
-    end
-  end
-
   # Build a single line summarizing existing commits being added in a merge
   # request
   #
@@ -392,7 +434,7 @@ class SystemNoteService
   #   "* ea0f8418 - 1 commit from branch `feature`"
   #
   # Returns a newline-terminated String
-  def self.existing_commit_summary(noteable, existing_commits, oldrev = nil)
+  def existing_commit_summary(noteable, existing_commits, oldrev = nil)
     return '' if existing_commits.empty?
 
     count = existing_commits.size
@@ -415,47 +457,7 @@ class SystemNoteService
     "* #{commit_ids} - #{commits_text} from branch `#{branch}`\n"
   end
 
-  # Called when the status of a Task has changed
-  #
-  # noteable  - Noteable object.
-  # project   - Project owning noteable
-  # author    - User performing the change
-  # new_task  - TaskList::Item object.
-  #
-  # Example Note text:
-  #
-  #   "Soandso marked the task Whatever as completed."
-  #
-  # Returns the created Note object
-  def self.change_task_status(noteable, project, author, new_task)
-    status_label = new_task.complete? ? Taskable::COMPLETED : Taskable::INCOMPLETE
-    body = "Marked the task **#{new_task.source}** as #{status_label}"
-    create_note(noteable: noteable, project: project, author: author, note: body)
-  end
-
-  # Called when noteable has been moved to another project
-  #
-  # direction    - symbol, :to or :from
-  # noteable     - Noteable object
-  # noteable_ref - Referenced noteable
-  # author       - User performing the move
-  #
-  # Example Note text:
-  #
-  #   "Moved to some_namespace/project_new#11"
-  #
-  # Returns the created Note object
-  def self.noteable_moved(noteable, project, noteable_ref, author, direction:)
-    unless [:to, :from].include?(direction)
-      raise ArgumentError, "Invalid direction `#{direction}`"
-    end
-
-    cross_reference = noteable_ref.to_reference(project)
-    body = "Moved #{direction} #{cross_reference}"
-    create_note(noteable: noteable, project: project, author: author, note: body)
-  end
-
-  def self.escape_html(text)
+  def escape_html(text)
     Rack::Utils.escape_html(text)
   end
 end
diff --git a/lib/banzai/filter/emoji_filter.rb b/lib/banzai/filter/emoji_filter.rb
index ae7d31cf191..2492b5213ac 100644
--- a/lib/banzai/filter/emoji_filter.rb
+++ b/lib/banzai/filter/emoji_filter.rb
@@ -38,6 +38,11 @@ module Banzai
         end
       end
 
+      # Build a regexp that matches all valid :emoji: names.
+      def self.emoji_pattern
+        @emoji_pattern ||= /:(#{Gitlab::Emoji.emojis_names.map { |name| Regexp.escape(name) }.join('|')}):/
+      end
+
       private
 
       def emoji_url(name)
@@ -59,11 +64,6 @@ module Banzai
         ActionController::Base.helpers.url_to_image(image)
       end
 
-      # Build a regexp that matches all valid :emoji: names.
-      def self.emoji_pattern
-        @emoji_pattern ||= /:(#{Gitlab::Emoji.emojis_names.map { |name| Regexp.escape(name) }.join('|')}):/
-      end
-
       def emoji_pattern
         self.class.emoji_pattern
       end
diff --git a/lib/banzai/filter/markdown_filter.rb b/lib/banzai/filter/markdown_filter.rb
index 9b209533a89..ff580ec68f8 100644
--- a/lib/banzai/filter/markdown_filter.rb
+++ b/lib/banzai/filter/markdown_filter.rb
@@ -12,7 +12,12 @@ module Banzai
         html
       end
 
-      private
+      def self.renderer
+        @renderer ||= begin
+          renderer = Redcarpet::Render::HTML.new
+          Redcarpet::Markdown.new(renderer, redcarpet_options)
+        end
+      end
 
       def self.redcarpet_options
         # https://github.com/vmg/redcarpet#and-its-like-really-simple-to-use
@@ -28,12 +33,7 @@ module Banzai
         }.freeze
       end
 
-      def self.renderer
-        @renderer ||= begin
-          renderer = Redcarpet::Render::HTML.new
-          Redcarpet::Markdown.new(renderer, redcarpet_options)
-        end
-      end
+      private_class_method :redcarpet_options
     end
   end
 end
diff --git a/lib/banzai/renderer.rb b/lib/banzai/renderer.rb
index 910687a7b6a..a4ae27eefd8 100644
--- a/lib/banzai/renderer.rb
+++ b/lib/banzai/renderer.rb
@@ -1,5 +1,7 @@
 module Banzai
   module Renderer
+    extend self
+
     # Convert a Markdown String into an HTML-safe String of HTML
     #
     # Note that while the returned HTML will have been sanitized of dangerous
@@ -14,7 +16,7 @@ module Banzai
     # context  - Hash of context options passed to our HTML Pipeline
     #
     # Returns an HTML-safe String
-    def self.render(text, context = {})
+    def render(text, context = {})
       cache_key = context.delete(:cache_key)
       cache_key = full_cache_key(cache_key, context[:pipeline])
 
@@ -52,7 +54,7 @@ module Banzai
     #    texts_and_contexts
     #    => [{ text: '### Hello',
     #          context: { cache_key: [note, :note] } }]
-    def self.cache_collection_render(texts_and_contexts)
+    def cache_collection_render(texts_and_contexts)
       items_collection = texts_and_contexts.each_with_index do |item, index|
         context = item[:context]
         cache_key = full_cache_multi_key(context.delete(:cache_key), context[:pipeline])
@@ -81,7 +83,7 @@ module Banzai
       items_collection.map { |item| item[:rendered] }
     end
 
-    def self.render_result(text, context = {})
+    def render_result(text, context = {})
       text = Pipeline[:pre_process].to_html(text, context) if text
 
       Pipeline[context[:pipeline]].call(text, context)
@@ -100,7 +102,7 @@ module Banzai
     #            :user      - User object
     #
     # Returns an HTML-safe String
-    def self.post_process(html, context)
+    def post_process(html, context)
       context = Pipeline[context[:pipeline]].transform_context(context)
 
       pipeline = Pipeline[:post_process]
@@ -113,7 +115,7 @@ module Banzai
 
     private
 
-    def self.cacheless_render(text, context = {})
+    def cacheless_render(text, context = {})
       Gitlab::Metrics.measure(:banzai_cacheless_render) do
         result = render_result(text, context)
 
@@ -126,7 +128,7 @@ module Banzai
       end
     end
 
-    def self.full_cache_key(cache_key, pipeline_name)
+    def full_cache_key(cache_key, pipeline_name)
       return unless cache_key
       ["banzai", *cache_key, pipeline_name || :full]
     end
@@ -134,7 +136,7 @@ module Banzai
     # To map Rails.cache.read_multi results we need to know the Rails.cache.expanded_key.
     # Other option will be to generate stringified keys on our side and don't delegate to Rails.cache.expanded_key
     # method.
-    def self.full_cache_multi_key(cache_key, pipeline_name)
+    def full_cache_multi_key(cache_key, pipeline_name)
       return unless cache_key
       Rails.cache.send(:expanded_key, full_cache_key(cache_key, pipeline_name))
     end
diff --git a/lib/gitlab/ci/config/node/configurable.rb b/lib/gitlab/ci/config/node/configurable.rb
index aedc28fe1d0..2de82d40c9d 100644
--- a/lib/gitlab/ci/config/node/configurable.rb
+++ b/lib/gitlab/ci/config/node/configurable.rb
@@ -40,7 +40,7 @@ module Gitlab
               Hash[(@nodes || {}).map { |key, factory| [key, factory.dup] }]
             end
 
-            private
+            private # rubocop:disable Lint/UselessAccessModifier
 
             def node(key, node, metadata)
               factory = Node::Factory.new(node)
diff --git a/lib/gitlab/database.rb b/lib/gitlab/database.rb
index 078609c86f1..55b8f888d53 100644
--- a/lib/gitlab/database.rb
+++ b/lib/gitlab/database.rb
@@ -55,12 +55,12 @@ module Gitlab
       end
     end
 
-    private
-
     def self.connection
       ActiveRecord::Base.connection
     end
 
+    private_class_method :connection
+
     def self.database_version
       row = connection.execute("SELECT VERSION()").first
 
@@ -70,5 +70,7 @@ module Gitlab
         row.first
       end
     end
+
+    private_class_method :database_version
   end
 end
diff --git a/lib/gitlab/diff/inline_diff.rb b/lib/gitlab/diff/inline_diff.rb
index 28ad637fda4..55708d42161 100644
--- a/lib/gitlab/diff/inline_diff.rb
+++ b/lib/gitlab/diff/inline_diff.rb
@@ -19,24 +19,6 @@ module Gitlab
 
       attr_accessor :old_line, :new_line, :offset
 
-      def self.for_lines(lines)
-        changed_line_pairs = self.find_changed_line_pairs(lines)
-
-        inline_diffs = []
-
-        changed_line_pairs.each do |old_index, new_index|
-          old_line = lines[old_index]
-          new_line = lines[new_index]
-
-          old_diffs, new_diffs = new(old_line, new_line, offset: 1).inline_diffs
-
-          inline_diffs[old_index] = old_diffs
-          inline_diffs[new_index] = new_diffs
-        end
-
-        inline_diffs
-      end
-
       def initialize(old_line, new_line, offset: 0)
         @old_line = old_line[offset..-1]
         @new_line = new_line[offset..-1]
@@ -63,32 +45,54 @@ module Gitlab
         [old_diffs, new_diffs]
       end
 
-      private
+      class << self
+        def for_lines(lines)
+          changed_line_pairs = find_changed_line_pairs(lines)
 
-      # Finds pairs of old/new line pairs that represent the same line that changed
-      def self.find_changed_line_pairs(lines)
-        # Prefixes of all diff lines, indicating their types
-        # For example: `" - +  -+  ---+++ --+  -++"`
-        line_prefixes = lines.each_with_object("") { |line, s| s << line[0] }.gsub(/[^ +-]/, ' ')
+          inline_diffs = []
 
-        changed_line_pairs = []
-        line_prefixes.scan(LINE_PAIRS_PATTERN) do
-          # For `"---+++"`, `begin_index == 0`, `end_index == 6`
-          begin_index, end_index = Regexp.last_match.offset(:del_ins)
+          changed_line_pairs.each do |old_index, new_index|
+            old_line = lines[old_index]
+            new_line = lines[new_index]
 
-          # For `"---+++"`, `changed_line_count == 3`
-          changed_line_count = (end_index - begin_index) / 2
+            old_diffs, new_diffs = new(old_line, new_line, offset: 1).inline_diffs
 
-          halfway_index = begin_index + changed_line_count
-          (begin_index...halfway_index).each do |i|
-            # For `"---+++"`, index 1 maps to 1 + 3 = 4
-            changed_line_pairs << [i, i + changed_line_count]
+            inline_diffs[old_index] = old_diffs
+            inline_diffs[new_index] = new_diffs
           end
+
+          inline_diffs
         end
 
-        changed_line_pairs
+        private
+
+        # Finds pairs of old/new line pairs that represent the same line that changed
+        def find_changed_line_pairs(lines)
+          # Prefixes of all diff lines, indicating their types
+          # For example: `" - +  -+  ---+++ --+  -++"`
+          line_prefixes = lines.each_with_object("") { |line, s| s << line[0] }.gsub(/[^ +-]/, ' ')
+
+          changed_line_pairs = []
+          line_prefixes.scan(LINE_PAIRS_PATTERN) do
+            # For `"---+++"`, `begin_index == 0`, `end_index == 6`
+            begin_index, end_index = Regexp.last_match.offset(:del_ins)
+
+            # For `"---+++"`, `changed_line_count == 3`
+            changed_line_count = (end_index - begin_index) / 2
+
+            halfway_index = begin_index + changed_line_count
+            (begin_index...halfway_index).each do |i|
+              # For `"---+++"`, index 1 maps to 1 + 3 = 4
+              changed_line_pairs << [i, i + changed_line_count]
+            end
+          end
+
+          changed_line_pairs
+        end
       end
 
+      private
+
       def longest_common_prefix(a, b)
         max_length = [a.length, b.length].max
 
diff --git a/lib/gitlab/metrics.rb b/lib/gitlab/metrics.rb
index 86a5b9a201a..081576a440c 100644
--- a/lib/gitlab/metrics.rb
+++ b/lib/gitlab/metrics.rb
@@ -141,10 +141,10 @@ module Gitlab
       end
     end
 
-    private
-
     def self.current_transaction
       Transaction.current
     end
+
+    private_class_method :current_transaction
   end
 end
diff --git a/lib/gitlab/themes.rb b/lib/gitlab/themes.rb
index 83f91de810c..d4020af76f9 100644
--- a/lib/gitlab/themes.rb
+++ b/lib/gitlab/themes.rb
@@ -2,6 +2,8 @@ module Gitlab
   # Module containing GitLab's application theme definitions and helper methods
   # for accessing them.
   module Themes
+    extend self
+
     # Theme ID used when no `default_theme` configuration setting is provided.
     APPLICATION_DEFAULT = 2
 
@@ -22,7 +24,7 @@ module Gitlab
     # classes that might be applied to the `body` element
     #
     # Returns a String
-    def self.body_classes
+    def body_classes
       THEMES.collect(&:css_class).uniq.join(' ')
     end
 
@@ -33,26 +35,26 @@ module Gitlab
     # id - Integer ID
     #
     # Returns a Theme
-    def self.by_id(id)
+    def by_id(id)
       THEMES.detect { |t| t.id == id } || default
     end
 
     # Returns the number of defined Themes
-    def self.count
+    def count
       THEMES.size
     end
 
     # Get the default Theme
     #
     # Returns a Theme
-    def self.default
+    def default
       by_id(default_id)
     end
 
     # Iterate through each Theme
     #
     # Yields the Theme object
-    def self.each(&block)
+    def each(&block)
       THEMES.each(&block)
     end
 
@@ -61,7 +63,7 @@ module Gitlab
     # user - User record
     #
     # Returns a Theme
-    def self.for_user(user)
+    def for_user(user)
       if user
         by_id(user.theme_id)
       else
@@ -71,7 +73,7 @@ module Gitlab
 
     private
 
-    def self.default_id
+    def default_id
       id = Gitlab.config.gitlab.default_theme.to_i
 
       # Prevent an invalid configuration setting from causing an infinite loop