Add subresource integrity for JS and CSS assets (#15096)

Fix #2744

lib/webpacker/helper_extensions.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+module Webpacker::HelperExtensions
+  def javascript_pack_tag(name, **options)
+    src, integrity = current_webpacker_instance.manifest.lookup!(name, type: :javascript, with_integrity: true)
+    javascript_include_tag(src, options.merge(integrity: integrity))
+  end
+
+  def stylesheet_pack_tag(name, **options)
+    src, integrity = current_webpacker_instance.manifest.lookup!(name, type: :stylesheet, with_integrity: true)
+    stylesheet_link_tag(src, options.merge(integrity: integrity))
+  end
+
+  def preload_pack_asset(name, **options)
+    src, integrity = current_webpacker_instance.manifest.lookup!(name, with_integrity: true)
+    preload_link_tag(src, options.merge(integrity: integrity))
+  end
+end
+
+Webpacker::Helper.prepend(Webpacker::HelperExtensions)

lib/webpacker/manifest_extensions.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+module Webpacker::ManifestExtensions
+  def lookup(name, pack_type = {})
+    asset = super
+
+    if pack_type[:with_integrity] && asset.respond_to?(:dig)
+      [asset.dig('src'), asset.dig('integrity')]
+    elsif asset.respond_to?(:dig)
+      asset.dig('src')
+    else
+      asset
+    end
+  end
+end
+
+Webpacker::Manifest.prepend(Webpacker::ManifestExtensions)