fix handleTOPIC only supporting modern RPL_TOPIC (#72)

handleTOPIC was using the wrong event parameters when a TOPIC message
or (old) RPL_TOPIC was received, it only handles (new) RPL_TOPIC messages
correctly.

TOPIC messages are defined as `TOPIC <channel> [:<topic>]` in both specs
while RPL_TOPIC differs between RFC1459/RFC2812 and "Modern IRC" such that
they are respectively defined as `RPC_TOPIC <channel> :<topic>` and
`RPL_TOPIC <client> <channel> :<topic>`.

The old code only correctly parsed the "Modern IRC" RPL_TOPIC variant and
not the (old) RPL_TOPIC or TOPIC events, these were instead silently never
used in state tracking of the channel topic.

builtin.go

@@ -223,14 +223,19 @@ func handlePART(c *Client, e Event) {
 // handleTOPIC handles incoming TOPIC events and keeps channel tracking info
 // updated with the latest channel topic.
 func handleTOPIC(c *Client, e Event) {
-	var name string
+	var name, topic string
 	switch len(e.Params) {
 	case 0:
 		return
-	case 1:
+	case 1: // TOPIC, message format is `TOPIC <channel>`
 		name = e.Params[0]
-	default:
+		topic = ""
+	case 2: // TOPIC, message format is `TOPIC <channel> :<topic>`
+		name = e.Params[0]
+		topic = e.Last()
+	default: // RPL_TOPIC, message format is `332 <client> <channel> :<topic>`
 		name = e.Params[1]
+		topic = e.Last()
 	}
 
 	c.state.Lock()
@@ -240,7 +245,7 @@ func handleTOPIC(c *Client, e Event) {
 		return
 	}
 
-	channel.Topic = e.Last()
+	channel.Topic = topic
 	c.state.Unlock()
 	c.state.notify(c, UPDATE_STATE)
 }

state_test.go

@@ -42,12 +42,13 @@ const mockConnStartState = `:dummy.int NOTICE * :*** Looking up your hostname...
 :dummy.int 354 nick 1 #channel nick2 other.int nick2 nick2 :realname2
 :dummy.int 315 nick #channel :End of /WHO list.
 :[email protected] JOIN #channel2 * :realname
-:dummy.int 332 nick #channel2 :example topic
+:dummy.int 332 nick #channel2 :example init topic
 :dummy.int 353 nick = #channel2 :[email protected] @[email protected]
 :dummy.int 366 nick #channel2 :End of /NAMES list.
 :dummy.int 354 nick 1 #channel2 ~user local.int nick 0 :realname
 :dummy.int 354 nick 1 #channel2 nick2 other.int nick2 nick2 :realname2
 :dummy.int 315 nick #channel2 :End of /WHO list.
+:dummy.int TOPIC #channel2 :example topic
 `
 
 const mockConnEndState = `:[email protected] QUIT :example reason
@@ -190,6 +191,10 @@ func TestState(t *testing.T) {
 			t.Fatal("User.InChannel() returned false for existing channel")
 		}
 
+		if ch2 := c.LookupChannel("#channel2"); ch2.Topic != "example topic" {
+			t.Fatalf("Channel.Topic == %q, want \"example topic\"", ch2.Topic)
+		}
+
 		finishStart <- true
 	})