Add shutdown_reason Websocket command

This allows changing the normal exit reason of Websocket
processes, providing a way to signal other processes of
why the exit occurred.

test/handlers/ws_shutdown_reason_commands_h.erl

@@ -0,0 +1,38 @@
+%% This module sends the process pid to the test pid
+%% found in the x-test-pid header, then changes the
+%% shutdown reason and closes the connection normally.
+
+-module(ws_shutdown_reason_commands_h).
+-behavior(cowboy_websocket).
+
+-export([init/2]).
+-export([websocket_init/1]).
+-export([websocket_handle/2]).
+-export([websocket_info/2]).
+
+init(Req, RunOrHibernate) ->
+	TestPid = list_to_pid(binary_to_list(cowboy_req:header(<<"x-test-pid">>, Req))),
+	{cowboy_websocket, Req, {TestPid, RunOrHibernate}}.
+
+websocket_init(State={TestPid, RunOrHibernate}) ->
+	TestPid ! {ws_pid, self()},
+	ShutdownReason = receive
+		{TestPid, SR} ->
+			SR
+	after 1000 ->
+		error(timeout)
+	end,
+	Commands = [
+		{shutdown_reason, ShutdownReason},
+		close
+	],
+	case RunOrHibernate of
+		run -> {Commands, State};
+		hibernate -> {Commands, State, hibernate}
+	end.
+
+websocket_handle(_, State) ->
+	{[], State}.
+
+websocket_info(_, State) ->
+	{[], State}.