Make sure we can only reply to an HTTP request inside Handler:handle.

Of course since requests are a record the response state can be explicitly
overriden, but standard use prevents errors by making sure only one reply
is sent.

src/cowboy_http_protocol.erl

@@ -143,7 +143,8 @@ handler_init(Req, State=#state{handler={Handler, Opts}}) ->
 -spec handler_loop(HandlerState::term(), Req::#http_req{},
 	State::#state{}) -> ok.
 handler_loop(HandlerState, Req, State=#state{handler={Handler, _Opts}}) ->
-	case catch Handler:handle(Req, HandlerState) of
+	case catch Handler:handle(Req#http_req{resp_state=waiting},
+			HandlerState) of
 		{ok, Req2, HandlerState2} ->
 			handler_terminate(HandlerState2, Req2, State);
 		{'EXIT', _Reason} ->
@@ -153,7 +154,8 @@ handler_loop(HandlerState, Req, State=#state{handler={Handler, _Opts}}) ->
 -spec handler_terminate(HandlerState::term(), Req::#http_req{},
 	State::#state{}) -> ok.
 handler_terminate(HandlerState, Req, State=#state{handler={Handler, _Opts}}) ->
-	Res = (catch Handler:terminate(Req, HandlerState)),
+	Res = (catch Handler:terminate(
+		Req#http_req{resp_state=locked}, HandlerState)),
 	%% @todo We need to check if the Req has been replied to.
 	%%       All requests must have a reply, at worst an error.
 	%%       If a request started but wasn't completed, complete it.

src/cowboy_http_req.erl

@@ -135,13 +135,14 @@ headers(Req) ->
 	Body::iolist(), Req::#http_req{}) -> ok.
 %% @todo Don't be naive about the headers!
 reply(Code, Headers, Body, Req=#http_req{socket=Socket,
-		transport=Transport, connection=Connection}) ->
+		transport=Transport, connection=Connection,
+		resp_state=waiting}) ->
 	StatusLine = ["HTTP/1.1 ", status(Code), "\r\n"],
 	BaseHeaders = ["Connection: ", atom_to_connection(Connection),
 		"\r\nContent-Length: ", integer_to_list(iolist_size(Body)), "\r\n"],
 	Transport:send(Socket,
 		[StatusLine, BaseHeaders, Headers, "\r\n", Body]),
-	{ok, Req}.
+	{ok, Req#http_req{resp_state=done}}.
 
 %% Internal.