Provide more helpful errors for invalid keys.

When it is first load, if an invalid key is present in `discord_format`
we inform the user of a fatal error and exit.
If it's on reload we don't apply the new format and inform the user such
was not done and that there is an error with an invalid key being
present in the `discord_format` setting.

bridge/irc_manager.go

@@ -361,15 +361,7 @@ func (m *IRCManager) SendMessage(channel string, msg *DiscordMessage) {
 
 	// Person is appearing offline (or the bridge is running in Simple Mode)
 	if !ok {
-		// length := len(msg.Author.Username)
 		for _, line := range strings.Split(content, "\n") {
-			// m.bridge.ircListener.Privmsg(channel, fmt.Sprintf(
-			// 	"<%s#%s> %s",
-			// 	msg.Author.Username[:1]+"\u200B"+msg.Author.Username[1:length],
-			// 	msg.Author.Discriminator,
-			// 	line,
-			// ))
-
 			m.bridge.ircListener.Privmsg(channel, m.formatIRCMessage(msg, line))
 		}
 		return

main.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"flag"
+	"fmt"
 	"os"
 	"os/signal"
 	"path/filepath"
@@ -85,8 +86,14 @@ func main() {
 		*insecure = viper.GetBool("insecure")
 	}
 	//
-	discordFormat := viper.GetStringMapString("discord_format")
-	discordFormat = setupDiscordFormat(discordFormat)
+	rawDiscordFormat := viper.GetStringMapString("discord_format")
+	var discordFormat map[string]string
+	if df, err := setupDiscordFormat(rawDiscordFormat); err == nil {
+		discordFormat = df
+	} else {
+		log.WithError(err).Fatal("discord_format setting is invalid")
+		return
+	}
 	//
 	viper.SetDefault("avatar_url", "https://ui-avatars.com/api/?name=${USERNAME}")
 	avatarURL := viper.GetString("avatar_url")
@@ -217,6 +224,14 @@ func main() {
 		}
 		dib.Config.DiscordIgnores = discordIgnores
 
+		rawDiscordFormat := viper.GetStringMapString("discord_format")
+		if discordFormat, err := setupDiscordFormat(rawDiscordFormat); err == nil {
+			dib.Config.DiscordFormat = discordFormat
+		} else {
+			log.WithError(err).Error("discord_format setting is invalid, this setting has not been updated")
+		}
+		dib.Config.IRCFormat = viper.GetString("irc_format")
+
 		chans := viper.GetStringMapString("channel_mappings")
 		equalChans := reflect.DeepEqual(chans, channelMappings)
 		if !equalChans {
@@ -257,7 +272,8 @@ func setupHostmaskMatchers(hostmasks []string) []glob.Glob {
 	return matchers
 }
 
-func setupDiscordFormat(discordFormat map[string]string) map[string]string {
+func setupDiscordFormat(discordFormat map[string]string) (map[string]string, error) {
+	var err error
 	// lowercase to match that YAML lowercases it
 	discordFormatDefaults := map[string]string{
 		"join": "_${NICK} joined (${IDENT}@${HOST})_",
@@ -272,7 +288,14 @@ func setupDiscordFormat(discordFormat map[string]string) map[string]string {
 		}
 	}
 
-	return discordFormat
+	for ev := range discordFormat {
+		if _, ok := discordFormatDefaults[ev]; !ok {
+			err = fmt.Errorf("Unknown format key %s", ev)
+			break
+		}
+	}
+
+	return discordFormat, err
 }
 
 func SetLogDebug(debug bool) {