Merge pull request rails#42338 from jhawthorn/send_preload_header_streaming

Skip sending preload links headers when streaming

Author: jhawthorn

actionview/lib/action_view/helpers/asset_tag_helper.rb

@@ -544,6 +544,7 @@ def resolve_link_as(extname, mime_type)
         MAX_HEADER_SIZE = 8_000 # Some HTTP client and proxies have a 8kiB header limit
         def send_preload_links_header(preload_links, max_header_size: MAX_HEADER_SIZE)
           return if preload_links.empty?
+          return if response.sending?
 
           if respond_to?(:request) && request
             request.send_early_hints("Link" => preload_links.join("\n"))

actionview/test/template/asset_tag_helper_test.rb

@@ -6,9 +6,22 @@
 require "action_dispatch"
 ActionView::Template::Types.delegate_to Mime
 
+module AssetTagHelperTestHelpers
+  def with_preload_links_header(new_preload_links_header = true)
+    original_preload_links_header = ActionView::Helpers::AssetTagHelper.preload_links_header
+    ActionView::Helpers::AssetTagHelper.preload_links_header = new_preload_links_header
+
+    yield
+  ensure
+    ActionView::Helpers::AssetTagHelper.preload_links_header = original_preload_links_header
+  end
+end
+
 class AssetTagHelperTest < ActionView::TestCase
   tests ActionView::Helpers::AssetTagHelper
 
+  include AssetTagHelperTestHelpers
+
   attr_reader :request, :response
 
   class FakeRequest
@@ -24,6 +37,7 @@ class FakeResponse
     def headers
       @headers ||= {}
     end
+    def sending?; false; end
   end
 
   def setup
@@ -788,16 +802,6 @@ def test_caching_image_path_with_caching_and_proc_asset_host_using_request
       assert_equal "http://localhost/images/xml.png", image_path("xml.png")
     end
   end
-
-  private
-    def with_preload_links_header(new_preload_links_header = true)
-      original_preload_links_header = ActionView::Helpers::AssetTagHelper.preload_links_header
-      ActionView::Helpers::AssetTagHelper.preload_links_header = new_preload_links_header
-
-      yield
-    ensure
-      ActionView::Helpers::AssetTagHelper.preload_links_header = original_preload_links_header
-    end
 end
 
 class AssetTagHelperNonVhostTest < ActionView::TestCase
@@ -951,6 +955,32 @@ def test_javascript_include_tag_without_request
   end
 end
 
+class AssetTagHelperWithStreamingRequest < ActionView::TestCase
+  tests ActionView::Helpers::AssetTagHelper
+
+  include AssetTagHelperTestHelpers
+
+  def setup
+    super
+    response.sending!
+  end
+
+  def test_stylesheet_link_tag_with_streaming
+    with_preload_links_header do
+      assert_dom_equal(
+        %(<link rel="stylesheet" href="/stylesheets/foo.css" />),
+        stylesheet_link_tag("foo.css")
+      )
+    end
+  end
+
+  def test_javascript_include_tag_with_streaming
+    with_preload_links_header do
+      assert_dom_equal %(<script src="/javascripts/foo.js"></script>), javascript_include_tag("foo.js")
+    end
+  end
+end
+
 class AssetUrlHelperControllerTest < ActionView::TestCase
   tests ActionView::Helpers::AssetUrlHelper