Fix NICK on upstreams supporting MONITOR

Previously, uc.network.Network.Nick wasn't successfully updated on
downstream NICK. This would cause soju to immediately switch back to the
old nick when the upstream supported MONITOR, so long as the network had
a nick configured as of initialization.

In addition, stop monitoring our desired nick once we've successfully
switched to it once, in order to not immediately undo server-induced
nick changes.

downstream.go

@@ -1838,6 +1838,7 @@ func (dc *downstreamConn) handleMessageRegistered(ctx context.Context, msg *irc.
 		}
 
 		if dc.network != nil {
+			dc.network.Network.Nick = nick
 			if uc := dc.upstream(); uc != nil {
 				uc.SendMessageLabeled(ctx, dc.id, &irc.Message{
 					Command: "NICK",

upstream.go

@@ -159,6 +159,8 @@ type upstreamConn struct {
 	regainNickBackoff *backoffer
 
 	gotMotd bool
+
+	hasDesiredNick bool
 }
 
 func connectToUpstream(ctx context.Context, network *network) (*upstreamConn, error) {
@@ -269,6 +271,7 @@ func connectToUpstream(ctx context.Context, network *network) (*upstreamConn, er
 		isupport:              make(map[string]*string),
 		pendingCmds:           make(map[string][]pendingUpstreamCommand),
 		monitored:             monitorCasemapMap{newCasemapMap()},
+		hasDesiredNick:        true,
 	}
 	return uc, nil
 }
@@ -948,6 +951,10 @@ func (uc *upstreamConn) handleMessage(ctx context.Context, msg *irc.Message) err
 				uc.pendingRegainNick = ""
 				uc.stopRegainNickTimer()
 			}
+			wantNick := database.GetNick(&uc.user.User, &uc.network.Network)
+			if uc.network.equalCasemap(wantNick, newNick) {
+				uc.hasDesiredNick = true
+			}
 		}
 
 		uc.channels.ForEach(func(ch *upstreamChannel) {
@@ -1581,7 +1588,7 @@ func (uc *upstreamConn) handleMessage(ctx context.Context, msg *irc.Message) err
 
 		// Check if the nick we want is now free
 		wantNick := database.GetNick(&uc.user.User, &uc.network.Network)
-		if !online && !uc.isOurNick(wantNick) {
+		if !online && !uc.isOurNick(wantNick) && !uc.hasDesiredNick {
 			found := false
 			for _, target := range targets {
 				prefix := irc.ParsePrefix(target)
@@ -1790,6 +1797,7 @@ func (uc *upstreamConn) handleMessage(ctx context.Context, msg *irc.Message) err
 		// servers have NICKLEN=30 so let's just use that.
 		if !uc.registered && len(uc.nick)+1 < 30 {
 			uc.nick = uc.nick + "_"
+			uc.hasDesiredNick = false
 			uc.logger.Printf("desired nick is not available, falling back to %q", uc.nick)
 			uc.SendMessage(ctx, &irc.Message{
 				Command: "NICK",
@@ -2238,7 +2246,8 @@ func (uc *upstreamConn) updateMonitor() {
 
 	wantNick := database.GetNick(&uc.user.User, &uc.network.Network)
 	wantNickCM := uc.network.casemap(wantNick)
-	if _, ok := add[wantNickCM]; !ok && !uc.monitored.Has(wantNick) && !uc.isOurNick(wantNick) {
+	if _, ok := add[wantNickCM]; !ok && !uc.monitored.Has(wantNick) &&
+			!uc.isOurNick(wantNick) && !uc.hasDesiredNick {
 		addList = append(addList, wantNickCM)
 		add[wantNickCM] = struct{}{}
 	}