Fix regression in autojoining with legacy tokens (slack). Fixes #651 (#848)

bridge/slack/legacy.go

@@ -13,7 +13,9 @@ type BLegacy struct {
 }
 
 func NewLegacy(cfg *bridge.Config) bridge.Bridger {
-	return &BLegacy{Bslack: newBridge(cfg)}
+	b := &BLegacy{Bslack: newBridge(cfg)}
+	b.legacy = true
+	return b
 }
 
 func (b *BLegacy) Connect() error {

bridge/slack/slack.go

@@ -32,6 +32,7 @@ type Bslack struct {
 
 	channels *channels
 	users    *users
+	legacy   bool
 }
 
 const (
@@ -151,6 +152,18 @@ func (b *Bslack) JoinChannel(channel config.ChannelInfo) error {
 		return nil
 	}
 
+	// try to join a channel when in legacy
+	if b.legacy {
+		_, err := b.sc.JoinChannel(channel.Name)
+		if err != nil {
+			switch err.Error() {
+			case "name_taken", "restricted_action":
+			case "default":
+				return err
+			}
+		}
+	}
+
 	b.channels.populateChannels(false)
 
 	channelInfo, err := b.channels.getChannel(channel.Name)
@@ -163,7 +176,8 @@ func (b *Bslack) JoinChannel(channel config.ChannelInfo) error {
 		channel.Name = channelInfo.Name
 	}
 
-	if !channelInfo.IsMember {
+	// we can't join a channel unless we are using legacy tokens #651
+	if !channelInfo.IsMember && !b.legacy {
 		return fmt.Errorf("slack integration that matterbridge is using is not member of channel '%s', please add it manually", channelInfo.Name)
 	}
 	return nil