From 6f688a4644d6e5c33f86b693fd54747871a76772 Mon Sep 17 00:00:00 2001
From: Shivaram Lingamneni <slingamn@cs.stanford.edu>
Date: Fri, 8 May 2020 05:44:40 -0400
Subject: [PATCH] fix #994

---
 irc/client.go   | 7 +------
 irc/commands.go | 6 ++++++
 irc/handlers.go | 6 ++++++
 3 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/irc/client.go b/irc/client.go
index 5007c0dd..a290adf4 100644
--- a/irc/client.go
+++ b/irc/client.go
@@ -661,12 +661,7 @@ func (client *Client) run(session *Session) {
 
 		cmd, exists := Commands[msg.Command]
 		if !exists {
-			if len(msg.Command) > 0 {
-				session.Send(nil, client.server.name, ERR_UNKNOWNCOMMAND, client.Nick(), msg.Command, client.t("Unknown command"))
-			} else {
-				session.Send(nil, client.server.name, ERR_UNKNOWNCOMMAND, client.Nick(), "lastcmd", client.t("No command given"))
-			}
-			continue
+			cmd = unknownCommand
 		}
 
 		isExiting := cmd.Run(client.server, client, session, msg)
diff --git a/irc/commands.go b/irc/commands.go
index 5cd48ea0..1ad9f484 100644
--- a/irc/commands.go
+++ b/irc/commands.go
@@ -73,6 +73,12 @@ func (cmd *Command) Run(server *Server, client *Client, session *Session, msg ir
 	return exiting
 }
 
+// fake handler for unknown commands (see #994: this ensures the response tags are correct)
+var unknownCommand = Command{
+	handler:      unknownCommandHandler,
+	usablePreReg: true,
+}
+
 // Commands holds all commands executable by a client connected to us.
 var Commands map[string]Command
 
diff --git a/irc/handlers.go b/irc/handlers.go
index 8f1e6ad7..bdf228fe 100644
--- a/irc/handlers.go
+++ b/irc/handlers.go
@@ -2760,3 +2760,9 @@ func zncHandler(server *Server, client *Client, msg ircmsg.IrcMessage, rb *Respo
 	zncModuleHandler(client, msg.Params[0], msg.Params[1:], rb)
 	return false
 }
+
+// fake handler for unknown commands
+func unknownCommandHandler(server *Server, client *Client, msg ircmsg.IrcMessage, rb *ResponseBuffer) bool {
+	rb.Add(nil, server.name, ERR_UNKNOWNCOMMAND, client.Nick(), utils.SafeErrorParam(msg.Command), client.t("Unknown command"))
+	return false
+}