upstream: decode ISUPPORT values

We don't really need to decode values for the ISUPPORT tokens we
care about, but maybe will in the future, and we re-encode them
when sending them to downstream. This resulted in double-encoded
NETWORK value for instance.

Author: emersion

upstream.go

@@ -998,7 +998,7 @@ func (uc *upstreamConn) handleMessage(ctx context.Context, msg *irc.Message) err
 				token = token[1:]
 			} else if i := strings.IndexByte(token, '='); i >= 0 {
 				parameter = token[:i]
-				value = token[i+1:]
+				value = xirc.DecodeIsupportValue(token[i+1:])
 				hasValue = true
 			}
 			parameter = strings.ToUpper(parameter)

xirc/genmsg.go

@@ -111,8 +111,6 @@ func GenerateIsupport(tokens []string) []*irc.Message {
 	return msgs
 }
 
-var isupportEncoder = strings.NewReplacer(" ", "\\x20", "\\", "\\x5C")
-
 func GenerateMOTD(motd string) []*irc.Message {
 	var msgs []*irc.Message
 	msgs = append(msgs, &irc.Message{

xirc/xirc.go

@@ -139,3 +139,12 @@ func (ms *MembershipSet) Remove(membership Membership) {
 		}
 	}
 }
+
+func DecodeIsupportValue(v string) string {
+	return isupportDecoder.Replace(v)
+}
+
+var (
+	isupportEncoder = strings.NewReplacer(" ", "\\x20", "\\", "\\x5C")
+	isupportDecoder = strings.NewReplacer("\\x20", " ", "\\x5C", "\\")
+)