don't preload for defered scripts and disable push

actionview/lib/action_view/helpers/asset_tag_helper.rb

@@ -90,7 +90,7 @@ def javascript_include_tag(*sources)
 
         sources_tags = sources.uniq.map { |source|
           href = path_to_javascript(source, path_options)
-          preload_links << "<#{href}>; rel=preload; as=script"
+          preload_links << "<#{href}>; rel=preload; as=script; nopush" unless options["defer"]
           tag_options = {
             "src" => href
           }.merge!(options)
@@ -140,7 +140,7 @@ def stylesheet_link_tag(*sources)
 
         sources_tags = sources.uniq.map { |source|
           href = path_to_stylesheet(source, path_options)
-          preload_links << "<#{href}>; rel=preload; as=style"
+          preload_links << "<#{href}>; rel=preload; as=style; nopush"
           tag_options = {
             "rel" => "stylesheet",
             "media" => "screen",

actionview/test/template/asset_tag_helper_test.rb

@@ -513,10 +513,15 @@ def test_javascript_include_tag_without_request
   def test_should_set_preload_links
     stylesheet_link_tag("http://example.com/style.css")
     javascript_include_tag("http://example.com/all.js")
-    expected = "<http://example.com/style.css>; rel=preload; as=style,<http://example.com/all.js>; rel=preload; as=script"
+    expected = "<http://example.com/style.css>; rel=preload; as=style; nopush,<http://example.com/all.js>; rel=preload; as=script; nopush"
     assert_equal expected, @response.headers["Link"]
   end
 
+  def test_should_not_preload_links_with_defer
+    javascript_include_tag("http://example.com/all.js", defer: true)
+    assert_equal "", @response.headers["Link"]
+  end
+
   def test_image_path
     ImagePathToTag.each { |method, tag| assert_dom_equal(tag, eval(method)) }
   end