Removes the Startup_CSS Feature flag

Reduces the Startup CSS Helper to only non spec

Updating to use always startup_css for a pipeline

Fixed loading spec for highlight stylesheet

Complete remove of the startupCss Helper

app/assets/javascripts/helpers/startup_css_helper.js

@@ -22,7 +22,7 @@ const handleStartupEvents = () => {
 
 /* For `waitForCSSLoaded` methods, see docs.gitlab.com/ee/development/fe_guide/performance.html#important-considerations */
 export const waitForCSSLoaded = (action = () => {}) => {
-  if (!gon?.features?.startupCss || allLinksLoaded()) {
+  if (allLinksLoaded()) {
     return new Promise((resolve) => {
       action();
       resolve();

app/helpers/application_helper.rb

@@ -4,8 +4,6 @@ require 'digest/md5'
 require 'uri'
 
 module ApplicationHelper
-  include StartupCssHelper
-
   # See https://docs.gitlab.com/ee/development/ee_features.html#code-in-appviews
   # rubocop: disable CodeReuse/ActiveRecord
   # We allow partial to be nil so that collection views can be passed in
@@ -250,11 +248,7 @@ module ApplicationHelper
   end
 
   def stylesheet_link_tag_defer(path)
-    if use_startup_css?
-      stylesheet_link_tag(path, media: "print", crossorigin: ActionController::Base.asset_host ? 'anonymous' : nil)
-    else
-      stylesheet_link_tag(path, media: "all")
-    end
+    stylesheet_link_tag(path, media: "print", crossorigin: ActionController::Base.asset_host ? 'anonymous' : nil)
   end
 
   def outdated_browser?

app/helpers/startup_css_helper.rb

-# frozen_string_literal: true
-
-module StartupCssHelper
-  def use_startup_css?
-    (Feature.enabled?(:startup_css) || params[:startup_css] == 'true' || cookies['startup_css'] == 'true') && !Rails.env.test?
-  end
-end

app/views/layouts/_head.html.haml

@@ -43,8 +43,6 @@
     = stylesheet_link_tag_defer "application"
     = yield :page_specific_styles
     = stylesheet_link_tag_defer "application_utilities"
-  - unless use_startup_css?
-    = stylesheet_link_tag_defer "themes/#{user_application_theme_css_filename}" if user_application_theme_css_filename
   = stylesheet_link_tag "disable_animations", media: "all" if Rails.env.test? || Gitlab.config.gitlab['disable_animations']
 
   = stylesheet_link_tag_defer "highlight/themes/#{user_color_scheme}"

app/views/layouts/_startup_css.haml

-- return unless use_startup_css?
-
 - startup_filename = current_path?("sessions#new") ? 'signin' : user_application_theme == 'gl-dark' ? 'dark' : 'general'
 
 %style{ type: "text/css" }

app/views/layouts/_startup_css_activation.haml

-- return unless use_startup_css?
-
 = javascript_tag do
   :plain
     document.querySelectorAll('link[media="print"]').forEach(linkTag => {

config/feature_flags/development/startup_css.yml

----
-name: startup_css
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/39713
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/238718
-milestone: '13.3'
-type: development
-group: group::editor
-default_enabled: false

lib/gitlab/gon_helper.rb

@@ -4,7 +4,6 @@
 
 module Gitlab
   module GonHelper
-    include StartupCssHelper
     include WebpackHelper
 
     def add_gon_variables
@@ -49,9 +48,6 @@ module Gitlab
       push_frontend_feature_flag(:usage_data_api, default_enabled: true)
       push_frontend_feature_flag(:security_auto_fix, default_enabled: false)
       push_frontend_feature_flag(:gl_tooltips, default_enabled: :yaml)
-
-      # Startup CSS feature is a special one as it can be enabled by means of cookies and params
-      gon.push({ features: { 'startupCss' => use_startup_css? } }, true)
     end
 
     # Exposes the state of a feature flag to the frontend code.

spec/frontend/helpers/startup_css_helper_spec.js

@@ -39,24 +39,7 @@ describe('waitForCSSLoaded', () => {
     });
   });
 
-  describe('with startup css disabled', () => {
-    gon.features = {
-      startupCss: false,
-    };
-
-    it('should invoke the action right away', async () => {
-      const events = waitForCSSLoaded(mockedCallback);
-      await events;
-
-      expect(mockedCallback).toHaveBeenCalledTimes(1);
-    });
-  });
-
   describe('with startup css enabled', () => {
-    gon.features = {
-      startupCss: true,
-    };
-
     it('should dispatch CSSLoaded when the assets are cached or already loaded', async () => {
       setFixtures(`
         <link href="one.css" data-startupcss="loaded">

spec/views/layouts/_head.html.haml_spec.rb

@@ -59,7 +59,7 @@ RSpec.describe 'layouts/_head' do
 
     render
 
-    expect(rendered).to match('<link rel="stylesheet" media="all" href="/stylesheets/highlight/themes/solarised-light.css" />')
+    expect(rendered).to match('<link rel="stylesheet" media="print" href="/stylesheets/highlight/themes/solarised-light.css" />')
   end
 
   context 'when an asset_host is set and snowplow url is set' do