configure webpack publicPath dynamically to account for CDN or relative path settings

2 files changed, 20 insertions, 15 deletions

diff --git a/app/assets/javascripts/webpack.js b/app/assets/javascripts/webpack.js
index 37420dcafa0..9a9cf395fb8 100644
--- a/app/assets/javascripts/webpack.js
+++ b/app/assets/javascripts/webpack.js
@@ -1,13 +1,9 @@
 /**
  * This is the first script loaded by webpack's runtime. It is used to manually configure
- * config.output.publicPath to account for relative_url_root settings which cannot be baked-in
- * to our webpack bundles.
+ * config.output.publicPath to account for relative_url_root or CDN settings which cannot be
+ * baked-in to our webpack bundles.
  */
 
-if (gon && gon.relative_url_root) {
-  // this assumes config.output.publicPath is an absolute path
-  const basePath = gon.relative_url_root.replace(/\/$/, '');
-
-  // eslint-disable-next-line camelcase, no-undef
-  __webpack_public_path__ = basePath + __webpack_public_path__;
+if (gon && gon.webpack_public_path) {
+  __webpack_public_path__ = gon.webpack_public_path; // eslint-disable-line
 }
diff --git a/app/helpers/webpack_helper.rb b/app/helpers/webpack_helper.rb
index 6bacda9fe75..0386df22374 100644
--- a/app/helpers/webpack_helper.rb
+++ b/app/helpers/webpack_helper.rb
@@ -11,20 +11,29 @@ module WebpackHelper
 
     paths = Webpack::Rails::Manifest.asset_paths(source)
     if extension
-      paths = paths.select { |p| p.ends_with? ".#{extension}" }
+      paths.select! { |p| p.ends_with? ".#{extension}" }
     end
 
-    # include full webpack-dev-server url for rspec tests running locally
+    force_host = webpack_public_host
+    if force_host
+      paths.map! { |p| "#{force_host}#{p}" }
+    end
+
+    paths
+  end
+
+  def webpack_public_host
     if Rails.env.test? && Rails.configuration.webpack.dev_server.enabled
       host = Rails.configuration.webpack.dev_server.host
       port = Rails.configuration.webpack.dev_server.port
       protocol = Rails.configuration.webpack.dev_server.https ? 'https' : 'http'
-
-      paths.map! do |p|
-        "#{protocol}://#{host}:#{port}#{p}"
-      end
+      "#{protocol}://#{host}:#{port}"
+    else
+      ActionController::Base.asset_host.try(:chomp, '/')
     end
+  end
 
-    paths
+  def webpack_public_path
+    "#{webpack_public_host}/#{Rails.application.config.webpack.public_path}/"
   end
 end