update webpack helper to automatically include route-based entry points

app/helpers/webpack_helper.rb

@@ -5,6 +5,24 @@ module WebpackHelper
     javascript_include_tag(*gitlab_webpack_asset_paths(bundle, force_same_domain: force_same_domain))
   end
 
+  def webpack_controller_bundle_tags
+    bundles = []
+    segments = [*controller.controller_path.split('/'), controller.action_name].compact
+
+    until segments.empty?
+      begin
+        asset_paths = gitlab_webpack_asset_paths("pages.#{segments.join('.')}", extension: 'js')
+        bundles.unshift(*asset_paths)
+      rescue Webpack::Rails::Manifest::EntryPointMissingError
+        # no bundle exists for this path
+      end
+
+      segments.pop
+    end
+
+    javascript_include_tag(*bundles)
+  end
+
   # override webpack-rails gem helper until changes can make it upstream
   def gitlab_webpack_asset_paths(source, extension: nil, force_same_domain: false)
     return "" unless source.present?

app/views/layouts/_head.html.haml

@@ -41,6 +41,7 @@
   = webpack_bundle_tag "webpack_runtime"
   = webpack_bundle_tag "common"
   = webpack_bundle_tag "main"
+  = webpack_controller_bundle_tags
   = webpack_bundle_tag "raven" if current_application_settings.clientside_sentry_enabled
   = webpack_bundle_tag "test" if Rails.env.test?