Stop setting SERVER_PORT env key if nil (#22)

According to the Rack specification, `env["SERVER_PORT"]` should either be a string containing decimal digits or not set at all.

Author: Francisco Mejia

lib/protocol/rack/adapter/rack2.rb

@@ -59,8 +59,12 @@ def make_environment(request)
 
 						# I'm not sure what sane defaults should be here:
 						CGI::SERVER_NAME => server_name,
-						CGI::SERVER_PORT => server_port,
 					}
+
+					# SERVER_PORT is optional but must not be set if it is not present.
+					if server_port
+						env[CGI::SERVER_PORT] = server_port
+					end
 
 					self.unwrap_request(request, env)
 

lib/protocol/rack/adapter/rack3.rb

@@ -55,8 +55,12 @@ def make_environment(request)
 
 						# I'm not sure what sane defaults should be here:
 						CGI::SERVER_NAME => server_name,
-						CGI::SERVER_PORT => server_port,
 					}
+
+					# SERVER_PORT is optional but must not be set if it is not present.
+					if server_port
+						env[CGI::SERVER_PORT] = server_port
+					end
 
 					self.unwrap_request(request, env)
 

lib/protocol/rack/adapter/rack31.rb

@@ -46,8 +46,12 @@ def make_environment(request)
 
 						# I'm not sure what sane defaults should be here:
 						CGI::SERVER_NAME => server_name,
-						CGI::SERVER_PORT => server_port,
 					}
+
+					# SERVER_PORT is optional but must not be set if it is not present.
+					if server_port
+						env[CGI::SERVER_PORT] = server_port
+					end
 
 					if body = request.body
 						if body.empty?

test/protocol/rack/adapter/generic.rb

@@ -35,6 +35,18 @@
 			expect(env).to have_keys("CONTENT_TYPE" => be == "text/plain")
 		end
 	end
+
+	with "app server without SERVER_PORT" do
+    let(:request) do
+      Protocol::HTTP::Request.new("https", "example.com", "GET", "/", "http/1.1", Protocol::HTTP::Headers[{"accept" => "text/html"}], nil)
+    end
+
+    it "does not include SERVER_PORT in the Rack environment" do
+      env = adapter.make_environment(request)
+      
+      expect(env).not.to have_keys(Protocol::Rack::CGI::SERVER_PORT)
+    end
+  end
 
 	with "a app that returns nil" do
 		include DisableConsoleContext