Merge branch '328741-preload-source-editor' into 'master'

Preload monaco globally

See merge request gitlab-org/gitlab!61112

app/helpers/webpack_helper.rb

@@ -5,6 +5,10 @@ module WebpackHelper
     javascript_include_tag(*webpack_entrypoint_paths(bundle))
   end
 
+  def webpack_preload_asset_tag(asset, options = {})
+    preload_link_tag(Gitlab::Webpack::Manifest.asset_paths(asset).first, options)
+  end
+
   def webpack_controller_bundle_tags
     chunks = []
 

app/views/layouts/_head.html.haml

@@ -32,6 +32,8 @@
   - if page_canonical_link
     %link{ rel: 'canonical', href: page_canonical_link }
 
+  = webpack_preload_asset_tag("monaco")
+
   = favicon_link_tag favicon, id: 'favicon', data: { original_href: favicon }, type: 'image/png'
 
   = render 'layouts/startup_css'

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

@@ -62,6 +62,12 @@ RSpec.describe 'layouts/_head' do
     expect(rendered).to match('<link rel="stylesheet" media="print" href="/stylesheets/highlight/themes/solarised-light.css" />')
   end
 
+  it 'preloads Monaco' do
+    render
+
+    expect(rendered).to match('<link rel="preload" href="/assets/webpack/monaco.chunk.js" as="script" type="text/javascript">')
+  end
+
   context 'when an asset_host is set and snowplow url is set' do
     let(:asset_host) { 'http://test.host' }
     let(:snowplow_collector_hostname) { 'www.snow.plow' }