Add early hints support

While not part of the rack spec, this API is exposed
by both puma and falcon, and Rails use it when available.

The 103 Early Hints response code is specified in RFC 8297.

1 files changed, 30 insertions, 0 deletions

diff --git a/test/unit/test_server.rb b/test/unit/test_server.rb
index 8096955..d706243 100644
--- a/test/unit/test_server.rb
+++ b/test/unit/test_server.rb
@@ -23,6 +23,16 @@ class TestHandler
   end
 end
 
+class TestEarlyHintsHandler
+  def call(env)
+    while env['rack.input'].read(4096)
+    end
+    env['rack.early_hints'].call(
+      "Link" => "</style.css>; rel=preload; as=style\n</script.js>; rel=preload"
+    )
+    [200, { 'Content-Type' => 'text/plain' }, ['hello!\n']]
+  end
+end
 
 class WebServerTest < Test::Unit::TestCase
 
@@ -84,6 +94,26 @@ class WebServerTest < Test::Unit::TestCase
     tmp.close!
   end
 
+  def test_early_hints
+    teardown
+    redirect_test_io do
+      @server = HttpServer.new(TestEarlyHintsHandler.new,
+                               :listeners => [ "127.0.0.1:#@port"],
+                               :early_hints => true)
+      @server.start
+    end
+
+    sock = TCPSocket.new('127.0.0.1', @port)
+    sock.syswrite("GET / HTTP/1.0\r\n\r\n")
+
+    responses = sock.sysread(4096)
+    assert_match %r{\AHTTP/1.[01] 103\b}, responses
+    assert_match %r{^Link: </style\.css>}, responses
+    assert_match %r{^Link: </script\.js>}, responses
+
+    assert_match %r{^HTTP/1.[01] 200\b}, responses
+  end
+
   def test_broken_app
     teardown
     app = lambda { |env| raise RuntimeError, "hello" }