reflect changes in Rack::Utils::HTTP_STATUS_CODES

Applications may want to alter the message associated with HTTP
status codes in Rack::Utils::HTTP_STATUS_CODES.  Avoid memoizing
status lines ahead-of-time

Note: this introduces a minor performance regression, but ought to
be unnoticeable unless you're running "Hello world"-type apps.

lib/unicorn/http_response.rb

@@ -10,25 +10,24 @@
 # is the job of Rack, with the exception of the "Date" and "Status" header.
 module Unicorn::HttpResponse
 
-  # Every standard HTTP code mapped to the appropriate message.
-  CODES = Rack::Utils::HTTP_STATUS_CODES.inject({}) { |hash,(code,msg)|
-    hash[code] = "#{code} #{msg}"
-    hash
-  }
   CRLF = "\r\n"
 
+  # internal API, code will always be common-enough-for-even-old-Rack
   def err_response(code, response_start_sent)
-    "#{response_start_sent ? '' : 'HTTP/1.1 '}#{CODES[code]}\r\n\r\n"
+    "#{response_start_sent ? '' : 'HTTP/1.1 '}" \
+      "#{code} #{Rack::Utils::HTTP_STATUS_CODES[code]}\r\n\r\n"
   end
 
   # writes the rack_response to socket as an HTTP response
   def http_response_write(socket, status, headers, body,
                           response_start_sent=false)
     hijack = nil
 
-    http_response_start = response_start_sent ? '' : 'HTTP/1.1 '
     if headers
-      buf = "#{http_response_start}#{CODES[status.to_i] || status}\r\n" \
+      code = status.to_i
+      msg = Rack::Utils::HTTP_STATUS_CODES[code]
+      start = response_start_sent ? ''.freeze : 'HTTP/1.1 '.freeze
+      buf = "#{start}#{msg ? %Q(#{code} #{msg}) : status}\r\n" \
             "Date: #{httpdate}\r\n" \
             "Connection: close\r\n"
       headers.each do |key, value|

test/unit/test_response.rb

@@ -79,4 +79,24 @@ def test_unknown_status_pass_through
     headers = out.string.split(/\r\n\r\n/).first.split(/\r\n/)
     assert %r{\AHTTP/\d\.\d 666 I AM THE BEAST\z}.match(headers[0])
   end
+
+  def test_modified_rack_http_status_codes_late
+    r, w = IO.pipe
+    pid = fork do
+      r.close
+      # Users may want to globally override the status text associated
+      # with an HTTP status code in their app.
+      Rack::Utils::HTTP_STATUS_CODES[200] = "HI"
+      http_response_write(w, 200, {}, [])
+      w.close
+    end
+    w.close
+    assert_equal "HTTP/1.1 200 HI\r\n", r.gets
+    r.read # just drain the pipe
+    pid, status = Process.waitpid2(pid)
+    assert_predicate status, :success?
+  ensure
+    r.close
+    w.close unless w.closed?
+  end
 end