Merge pull request #30744 from eileencodes/early-hints

Implement H2 Early Hints for Rails

3 files changed, 34 insertions, 5 deletions

diff --git a/actionview/lib/action_view/helpers/asset_tag_helper.rb b/actionview/lib/action_view/helpers/asset_tag_helper.rb
index bc2713d13e..f4f1030ac4 100644
--- a/actionview/lib/action_view/helpers/asset_tag_helper.rb
+++ b/actionview/lib/action_view/helpers/asset_tag_helper.rb
@@ -37,6 +37,9 @@ module ActionView
       # When the Asset Pipeline is enabled, you can pass the name of your manifest as
       # source, and include other JavaScript or CoffeeScript files inside the manifest.
       #
+      # If the server supports Early Hints header links for these assets will be
+      # automatically pushed.
+      #
       # ==== Options
       #
       # When the last parameter is a hash you can add HTML attributes using that
@@ -77,12 +80,20 @@ module ActionView
       def javascript_include_tag(*sources)
         options = sources.extract_options!.stringify_keys
         path_options = options.extract!("protocol", "extname", "host", "skip_pipeline").symbolize_keys
-        sources.uniq.map { |source|
+        early_hints_links = []
+
+        sources_tags = sources.uniq.map { |source|
+          href = path_to_javascript(source, path_options)
+          early_hints_links << "<#{href}>; rel=preload; as=script"
           tag_options = {
-            "src" => path_to_javascript(source, path_options)
+            "src" => href
           }.merge!(options)
           content_tag("script".freeze, "", tag_options)
         }.join("\n").html_safe
+
+        request.send_early_hints("Link" => early_hints_links.join("\n"))
+
+        sources_tags
       end
 
       # Returns a stylesheet link tag for the sources specified as arguments. If
@@ -92,6 +103,9 @@ module ActionView
       # to "screen", so you must explicitly set it to "all" for the stylesheet(s) to
       # apply to all media types.
       #
+      # If the server supports Early Hints header links for these assets  will be
+      # automatically pushed.
+      #
       #   stylesheet_link_tag "style"
       #   # => <link href="/assets/style.css" media="screen" rel="stylesheet" />
       #
@@ -113,14 +127,22 @@ module ActionView
       def stylesheet_link_tag(*sources)
         options = sources.extract_options!.stringify_keys
         path_options = options.extract!("protocol", "host", "skip_pipeline").symbolize_keys
-        sources.uniq.map { |source|
+        early_hints_links = []
+
+        sources_tags = sources.uniq.map { |source|
+          href = path_to_stylesheet(source, path_options)
+          early_hints_links << "<#{href}>; rel=preload; as=stylesheet"
           tag_options = {
             "rel" => "stylesheet",
             "media" => "screen",
-            "href" => path_to_stylesheet(source, path_options)
+            "href" => href
           }.merge!(options)
           tag(:link, tag_options)
         }.join("\n").html_safe
+
+        request.send_early_hints("Link" => early_hints_links.join("\n"))
+
+        sources_tags
       end
 
       # Returns a link tag that browsers and feed readers can use to auto-detect
diff --git a/actionview/test/template/asset_tag_helper_test.rb b/actionview/test/template/asset_tag_helper_test.rb
index 182d8f89f7..7475f5cc3c 100644
--- a/actionview/test/template/asset_tag_helper_test.rb
+++ b/actionview/test/template/asset_tag_helper_test.rb
@@ -19,6 +19,7 @@ class AssetTagHelperTest < ActionView::TestCase
       def ssl?() false end
       def host_with_port() "localhost" end
       def base_url() "http://www.example.com" end
+      def send_early_hints(links) end
     end.new
 
     @controller.request = @request
@@ -653,7 +654,9 @@ class AssetTagHelperNonVhostTest < ActionView::TestCase
     @controller = BasicController.new
     @controller.config.relative_url_root = "/collaboration/hieraki"
 
-    @request = Struct.new(:protocol, :base_url).new("gopher://", "gopher://www.example.com")
+    @request = Struct.new(:protocol, :base_url) do
+      def send_early_hints(links); end
+    end.new("gopher://", "gopher://www.example.com")
     @controller.request = @request
   end
 
diff --git a/actionview/test/template/javascript_helper_test.rb b/actionview/test/template/javascript_helper_test.rb
index 4478c9f4ab..a72bc6c2fe 100644
--- a/actionview/test/template/javascript_helper_test.rb
+++ b/actionview/test/template/javascript_helper_test.rb
@@ -6,11 +6,15 @@ class JavaScriptHelperTest < ActionView::TestCase
   tests ActionView::Helpers::JavaScriptHelper
 
   attr_accessor :output_buffer
+  attr_reader :request
 
   setup do
     @old_escape_html_entities_in_json = ActiveSupport.escape_html_entities_in_json
     ActiveSupport.escape_html_entities_in_json = true
     @template = self
+    @request = Class.new do
+      def send_early_hints(links) end
+    end.new
   end
 
   def teardown