Enable frozen string for app/helpers/**/*.rb

Partially addresses #47424.

app/helpers/accounts_helper.rb

+# frozen_string_literal: true
+
 module AccountsHelper
   def incoming_email_token_enabled?
     current_user.incoming_email_token && Gitlab::IncomingEmail.supports_issue_creation?

app/helpers/active_sessions_helper.rb

+# frozen_string_literal: true
+
 module ActiveSessionsHelper
   # Maps a device type as defined in `ActiveSession` to an svg icon name and
   # outputs the icon html.

app/helpers/appearances_helper.rb

+# frozen_string_literal: true
+
 module AppearancesHelper
   def brand_title
     current_appearance&.title.presence || 'GitLab Community Edition'

app/helpers/application_helper.rb

+# frozen_string_literal: true
+
 require 'digest/md5'
 require 'uri'
 
@@ -106,11 +108,11 @@ def extra_config
   #
   # Returns an HTML-safe String
   def time_ago_with_tooltip(time, placement: 'top', html_class: '', short_format: false)
-    css_classes = short_format ? 'js-short-timeago' : 'js-timeago'
-    css_classes << " #{html_class}" unless html_class.blank?
+    css_classes = [short_format ? 'js-short-timeago' : 'js-timeago']
+    css_classes << html_class unless html_class.blank?
 
     element = content_tag :time, l(time, format: "%b %d, %Y"),
-      class: css_classes,
+      class: css_classes.join(' '),
       title: l(time.to_time.in_time_zone, format: :timeago_tooltip),
       datetime: time.to_time.getutc.iso8601,
       data: {

app/helpers/application_settings_helper.rb

+# frozen_string_literal: true
+
 module ApplicationSettingsHelper
   extend self
 
@@ -73,12 +75,12 @@ def import_sources_checkboxes(help_block_id, options = {})
   def oauth_providers_checkboxes
     button_based_providers.map do |source|
       disabled = Gitlab::CurrentSettings.disabled_oauth_sign_in_sources.include?(source.to_s)
-      css_class = 'btn'
-      css_class << ' active' unless disabled
+      css_class = ['btn']
+      css_class << 'active' unless disabled
       checkbox_name = 'application_setting[enabled_oauth_sign_in_sources][]'
       name = Gitlab::Auth::OAuth::Provider.label_for(source)
 
-      label_tag(checkbox_name, class: css_class) do
+      label_tag(checkbox_name, class: css_class.join(' ')) do
         check_box_tag(checkbox_name, source, !disabled,
                       autocomplete: 'off',
                       id: name.tr(' ', '_')) + name

app/helpers/auth_helper.rb

+# frozen_string_literal: true
+
 module AuthHelper
   PROVIDERS_WITH_ICONS = %w(twitter github gitlab bitbucket google_oauth2 facebook azure_oauth2 authentiq).freeze
   LDAP_PROVIDER = /\Aldap/

app/helpers/auto_devops_helper.rb

+# frozen_string_literal: true
+
 module AutoDevopsHelper
   def show_auto_devops_callout?(project)
     Feature.get(:auto_devops_banner_disabled).off? &&

app/helpers/avatars_helper.rb

+# frozen_string_literal: true
+
 module AvatarsHelper
   def project_icon(project_id, options = {})
     source_icon(Project, project_id, options)
@@ -125,9 +127,9 @@ def source_icon(klass, source_id, options = {})
 
   def source_identicon(source, options = {})
     bg_key = (source.id % 7) + 1
-    options[:class] ||= ''
-    options[:class] << ' identicon'
-    options[:class] << " bg#{bg_key}"
+
+    options[:class] =
+      [*options[:class], "identicon bg#{bg_key}"].join(' ')
 
     content_tag(:div, class: options[:class].strip) do
       source.name[0, 1].upcase

app/helpers/award_emoji_helper.rb

+# frozen_string_literal: true
+
 module AwardEmojiHelper
   def toggle_award_url(awardable)
     return url_for([:toggle_award_emoji, awardable]) unless @project || awardable.is_a?(Note)

app/helpers/blame_helper.rb

+# frozen_string_literal: true
+
 module BlameHelper
   def age_map_duration(blame_groups, project)
     now = Time.zone.now

app/helpers/blob_helper.rb

+# frozen_string_literal: true
+
 module BlobHelper
   def highlight(blob_name, blob_content, repository: nil, plain: false)
     plain ||= blob_content.length > Blob::MAXIMUM_TEXT_HIGHLIGHT_SIZE

app/helpers/boards_helper.rb

+# frozen_string_literal: true
+
 module BoardsHelper
   def board
     @board ||= @board || @boards.first

app/helpers/branches_helper.rb

+# frozen_string_literal: true
+
 module BranchesHelper
   def project_branches
     options_for_select(@project.repository.branch_names, @project.default_branch)

app/helpers/breadcrumbs_helper.rb

+# frozen_string_literal: true
+
 module BreadcrumbsHelper
   def add_to_breadcrumbs(text, link)
     @breadcrumbs_extra_links ||= []

app/helpers/broadcast_messages_helper.rb

+# frozen_string_literal: true
+
 module BroadcastMessagesHelper
   def broadcast_message(message)
     return unless message.present?
@@ -8,18 +10,17 @@ def broadcast_message(message)
   end
 
   def broadcast_message_style(broadcast_message)
-    style = ''
+    style = []
 
     if broadcast_message.color.present?
       style << "background-color: #{broadcast_message.color}"
-      style << '; ' if broadcast_message.font.present?
     end
 
     if broadcast_message.font.present?
       style << "color: #{broadcast_message.font}"
     end
 
-    style
+    style.join('; ')
   end
 
   def broadcast_message_status(broadcast_message)

app/helpers/builds_helper.rb

+# frozen_string_literal: true
+
 module BuildsHelper
   def build_summary(build, skip: false)
     if build.has_trace?
@@ -12,10 +14,10 @@ def build_summary(build, skip: false)
   end
 
   def sidebar_build_class(build, current_build)
-    build_class = ''
-    build_class += ' active' if build.id === current_build.id
-    build_class += ' retried' if build.retried?
-    build_class
+    build_class = []
+    build_class << 'active' if build.id === current_build.id
+    build_class << 'retried' if build.retried?
+    build_class.join(' ')
   end
 
   def javascript_build_options

app/helpers/button_helper.rb

+# frozen_string_literal: true
+
 module ButtonHelper
   # Output a "Copy to Clipboard" button
   #

app/helpers/calendar_helper.rb

+# frozen_string_literal: true
+
 module CalendarHelper
   def calendar_url_options
     { format: :ics,

app/helpers/ci_status_helper.rb

+# frozen_string_literal: true
+
 ##
 # DEPRECATED
 #

app/helpers/clusters_helper.rb

+# frozen_string_literal: true
+
 module ClustersHelper
   def has_multiple_clusters?(project)
     false

app/helpers/commits_helper.rb

+# frozen_string_literal: true
+
 module CommitsHelper
   # Returns a link to the commit author. If the author has a matching user and
   # is a member of the current @project it will link to the team member page.

app/helpers/compare_helper.rb

+# frozen_string_literal: true
+
 module CompareHelper
   def create_mr_button?(from = params[:from], to = params[:to], project = @project)
     from.present? &&

app/helpers/components_helper.rb

+# frozen_string_literal: true
+
 module ComponentsHelper
   def gitlab_workhorse_version
     if request.headers['Gitlab-Workhorse'].present?

app/helpers/conversational_development_index_helper.rb

+# frozen_string_literal: true
+
 module ConversationalDevelopmentIndexHelper
   def score_level(score)
     if score < 33.33

app/helpers/count_helper.rb

+# frozen_string_literal: true
+
 module CountHelper
   def approximate_count_with_delimiters(count_data, model)
     count = count_data[model]

app/helpers/dashboard_helper.rb

+# frozen_string_literal: true
+
 module DashboardHelper
   def assigned_issues_dashboard_path
     issues_dashboard_path(assignee_id: current_user.id)

app/helpers/defer_script_tag_helper.rb

+# frozen_string_literal: true
+
 module DeferScriptTagHelper
   # Override the default ActionView `javascript_include_tag` helper to support page specific deferred loading
   def javascript_include_tag(*sources)

app/helpers/deploy_tokens_helper.rb

+# frozen_string_literal: true
+
 module DeployTokensHelper
   def expand_deploy_tokens_section?(deploy_token)
     deploy_token.persisted? ||

app/helpers/diff_helper.rb

+# frozen_string_literal: true
+
 module DiffHelper
   def mark_inline_diffs(old_line, new_line)
     old_diffs, new_diffs = Gitlab::Diff::InlineDiff.new(old_line, new_line).inline_diffs
@@ -39,7 +41,8 @@ def diff_match_line(old_pos, new_pos, text: '', view: :inline, bottom: false)
     line_num_class = %w[diff-line-num unfold js-unfold]
     line_num_class << 'js-unfold-bottom' if bottom
 
-    html = ''
+    html = []
+
     if old_pos
       html << content_tag(:td, '...', class: [*line_num_class, 'old_line'], data: { linenumber: old_pos })
       html << content_tag(:td, text, class: [*content_line_class, 'left-side']) if view == :parallel
@@ -50,7 +53,7 @@ def diff_match_line(old_pos, new_pos, text: '', view: :inline, bottom: false)
       html << content_tag(:td, text, class: [*content_line_class, ('right-side' if view == :parallel)])
     end
 
-    html.html_safe
+    html.join.html_safe
   end
 
   def diff_line_content(line)
@@ -215,9 +218,7 @@ def params_with_whitespace
   end
 
   def toggle_whitespace_link(url, options)
-    options[:class] ||= ''
-    options[:class] << ' btn btn-default'
-
+    options[:class] = [*options[:class], 'btn btn-default'].join(' ')
     link_to "#{hide_whitespace? ? 'Show' : 'Hide'} whitespace changes", url, class: options[:class]
   end
 

app/helpers/dropdowns_helper.rb

+# frozen_string_literal: true
+
 module DropdownsHelper
   def dropdown_tag(toggle_text, options: {}, &block)
     content_tag :div, class: "dropdown #{options[:wrapper_class] if options.key?(:wrapper_class)}" do
@@ -10,7 +12,7 @@ def dropdown_tag(toggle_text, options: {}, &block)
       dropdown_output = dropdown_toggle(toggle_text, data_attr, options)
 
       dropdown_output << content_tag(:div, class: "dropdown-menu dropdown-select #{options[:dropdown_class] if options.key?(:dropdown_class)}") do
-        output = ""
+        output = []
 
         if options.key?(:title)
           output << dropdown_title(options[:title])
@@ -31,8 +33,7 @@ def dropdown_tag(toggle_text, options: {}, &block)
         end
 
         output << dropdown_loading
-
-        output.html_safe
+        output.join.html_safe
       end
 
       dropdown_output.html_safe
@@ -50,7 +51,7 @@ def dropdown_toggle(toggle_text, data_attr, options = {})
 
   def dropdown_title(title, options: {})
     content_tag :div, class: "dropdown-title" do
-      title_output = ""
+      title_output = []
 
       if options.fetch(:back, false)
         title_output << content_tag(:button, class: "dropdown-title-button dropdown-menu-back", aria: { label: "Go back" }, type: "button") do
@@ -66,7 +67,7 @@ def dropdown_title(title, options: {})
         end
       end
 
-      title_output.html_safe
+      title_output.join.html_safe
     end
   end
 

app/helpers/emails_helper.rb

+# frozen_string_literal: true
+
 module EmailsHelper
   include AppearancesHelper
 
@@ -49,8 +51,8 @@ def password_reset_token_valid_time
 
   def reset_token_expire_message
     link_tag = link_to('request a new one', new_user_password_url(user_email: @user.email))
-    msg = "This link is valid for #{password_reset_token_valid_time}.  "
-    msg << "After it expires, you can #{link_tag}."
+    "This link is valid for #{password_reset_token_valid_time}.  " \
+    "After it expires, you can #{link_tag}."
   end
 
   def header_logo

app/helpers/emoji_helper.rb

+# frozen_string_literal: true
+
 module EmojiHelper
   def emoji_icon(*args)
     raw Gitlab::Emoji.gl_emoji_tag(*args)

app/helpers/environment_helper.rb

+# frozen_string_literal: true
+
 module EnvironmentHelper
   def environment_for_build(project, build)
     return unless build.environment

app/helpers/environments_helper.rb

+# frozen_string_literal: true
+
 module EnvironmentsHelper
   def environments_list_data
     {

app/helpers/events_helper.rb

+# frozen_string_literal: true
+
 module EventsHelper
   ICON_NAMES_BY_EVENT_TYPE = {
     'pushed to' => 'commit',

app/helpers/explore_helper.rb

+# frozen_string_literal: true
+
 module ExploreHelper
   def filter_projects_path(options = {})
     exist_opts = {

app/helpers/external_wiki_helper.rb

+# frozen_string_literal: true
+
 module ExternalWikiHelper
   def get_project_wiki_path(project)
     external_wiki_service = project.external_wiki

app/helpers/favicon_helper.rb

+# frozen_string_literal: true
+
 module FaviconHelper
   def favicon_extension_whitelist
     FaviconUploader::EXTENSION_WHITELIST

app/helpers/form_helper.rb

+# frozen_string_literal: true
+
 module FormHelper
   def form_errors(model, type: 'form')
     return unless model.errors.any?

app/helpers/git_helper.rb

+# frozen_string_literal: true
+
 module GitHelper
   def strip_gpg_signature(text)
     text.gsub(/-----BEGIN PGP SIGNATURE-----(.*)-----END PGP SIGNATURE-----/m, "")

app/helpers/gitlab_routing_helper.rb

+# frozen_string_literal: true
+
 # Shorter routing method for some project items
 module GitlabRoutingHelper
   extend ActiveSupport::Concern

app/helpers/graph_helper.rb

+# frozen_string_literal: true
+
 module GraphHelper
   def refs(repo, commit)
-    refs = commit.ref_names(repo).join(' ')
+    refs = [commit.ref_names(repo).join(' ')]
 
     # append note count
     notes_count = @graph.notes[commit.id]
     refs << "[#{pluralize(notes_count, 'note')}]" if notes_count > 0
 
-    refs
+    refs.join
   end
 
   def parents_zip_spaces(parents, parent_spaces)

app/helpers/groups_helper.rb

+# frozen_string_literal: true
+
 module GroupsHelper
   def group_nav_link_paths
     %w[groups#projects groups#edit badges#index ci_cd#show ldap_group_links#index hooks#index audit_events#index pipeline_quota#index]
@@ -43,22 +45,22 @@ def group_icon_url(group, options = {})
 
   def group_title(group, name = nil, url = nil)
     @has_group_title = true
-    full_title = ''
+    full_title = []
 
     group.ancestors.reverse.each_with_index do |parent, index|
       if index > 0
         add_to_breadcrumb_dropdown(group_title_link(parent, hidable: false, show_avatar: true, for_dropdown: true), location: :before)
       else
-        full_title += breadcrumb_list_item group_title_link(parent, hidable: false)
+        full_title << breadcrumb_list_item(group_title_link(parent, hidable: false))
       end
     end
 
-    full_title += render "layouts/nav/breadcrumbs/collapsed_dropdown", location: :before, title: _("Show parent subgroups")
+    full_title << render("layouts/nav/breadcrumbs/collapsed_dropdown", location: :before, title: _("Show parent subgroups"))
 
-    full_title += breadcrumb_list_item group_title_link(group)
-    full_title += ' &middot; '.html_safe + link_to(simple_sanitize(name), url, class: 'group-path breadcrumb-item-text js-breadcrumb-item-text') if name
+    full_title << breadcrumb_list_item(group_title_link(group))
+    full_title << ' &middot; '.html_safe + link_to(simple_sanitize(name), url, class: 'group-path breadcrumb-item-text js-breadcrumb-item-text') if name
 
-    full_title.html_safe
+    full_title.join.html_safe
   end
 
   def projects_lfs_status(group)
@@ -138,15 +140,8 @@ def get_group_sidebar_links
 
   def group_title_link(group, hidable: false, show_avatar: false, for_dropdown: false)
     link_to(group_path(group), class: "group-path #{'breadcrumb-item-text' unless for_dropdown} js-breadcrumb-item-text #{'hidable' if hidable}") do
-      output =
-        if (group.try(:avatar_url) || show_avatar) && !Rails.env.test?
-          group_icon(group, class: "avatar-tile", width: 15, height: 15)
-        else
-          ""
-        end
-
-      output << simple_sanitize(group.name)
-      output.html_safe
+      icon = group_icon(group, class: "avatar-tile", width: 15, height: 15) if (group.try(:avatar_url) || show_avatar) && !Rails.env.test?
+      [icon, simple_sanitize(group.name)].join.html_safe
     end
   end
 

app/helpers/hooks_helper.rb

+# frozen_string_literal: true
+
 module HooksHelper
   def link_to_test_hook(hook, trigger)
     path = case hook

app/helpers/icons_helper.rb

+# frozen_string_literal: true
+
 require 'json'
 
 module IconsHelper
@@ -47,9 +49,10 @@ def sprite_icon(icon_name, size: nil, css_class: nil)
       end
     end
 
-    css_classes = size ? "s#{size}" : ""
-    css_classes << " #{css_class}" unless css_class.blank?
-    content_tag(:svg, content_tag(:use, "", { "xlink:href" => "#{sprite_icon_path}##{icon_name}" } ), class: css_classes.empty? ? nil : css_classes)
+    css_classes = []
+    css_classes << "s#{size}" if size
+    css_classes << "#{css_class}" unless css_class.blank?
+    content_tag(:svg, content_tag(:use, "", { "xlink:href" => "#{sprite_icon_path}##{icon_name}" } ), class: css_classes.empty? ? nil : css_classes.join(' '))
   end
 
   def external_snippet_icon(name)
@@ -70,10 +73,10 @@ def audit_icon(names, options = {})
   end
 
   def spinner(text = nil, visible = false)
-    css_class = 'loading'
-    css_class << ' hide' unless visible
+    css_class = ['loading']
+    css_class << 'hide' unless visible
 
-    content_tag :div, class: css_class do
+    content_tag :div, class: css_class.join(' ') do
       icon('spinner spin') + text
     end
   end
@@ -97,9 +100,10 @@ def visibility_level_icon(level, fw: true, options: {})
         'globe'
       end
 
-    name << " fw" if fw
+    name = [name]
+    name << "fw" if fw
 
-    icon(name, options)
+    icon(name.join(' '), options)
   end
 
   def file_type_icon_class(type, mode, name)

app/helpers/import_helper.rb

+# frozen_string_literal: true
+
 module ImportHelper
   include ::Gitlab::Utils::StrongMemoize
 

app/helpers/instance_configuration_helper.rb

+# frozen_string_literal: true
+
 module InstanceConfigurationHelper
   def instance_configuration_cell_html(value, &block)
     return '-' unless value.to_s.presence

app/helpers/issuables_helper.rb

+# frozen_string_literal: true
+
 module IssuablesHelper
   include GitlabRoutingHelper
 
@@ -167,8 +169,9 @@ def to_url_reference(issuable)
   end
 
   def issuable_meta(issuable, project, text)
-    output = ""
+    output = []
     output << "Opened #{time_ago_with_tooltip(issuable.created_at)} by ".html_safe
+
     output << content_tag(:strong) do
       author_output = link_to_member(project, issuable.author, size: 24, mobile_classes: "d-none d-sm-inline", tooltip: true)
       author_output << link_to_member(project, issuable.author, size: 24, by_username: true, avatar: false, mobile_classes: "d-block d-sm-none")
@@ -185,7 +188,7 @@ def issuable_meta(issuable, project, text)
     output << content_tag(:span, (issuable.task_status if issuable.tasks?), id: "task_status", class: "d-none d-sm-none d-md-inline-block")
     output << content_tag(:span, (issuable.task_status_short if issuable.tasks?), id: "task_status_short", class: "d-md-none")
 
-    output.html_safe
+    output.join.html_safe
   end
 
   def issuable_todo(issuable)

app/helpers/issues_helper.rb

+# frozen_string_literal: true
+
 module IssuesHelper