PLT-6556 Fixed last member of a channel not being able to delete channel with api v4 (#6397)

api4/channel.go

@@ -482,6 +482,14 @@ func deleteChannel(c *Context, w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	var memberCount int64
+	if memberCount, err = app.GetChannelMemberCount(c.Params.ChannelId); err != nil {
+		c.Err = err
+		return
+	}
+
+	// Allow delete if user is the only member left in channel
+	if memberCount > 1 {
 		if channel.Type == model.CHANNEL_OPEN && !app.SessionHasPermissionToChannel(c.Session, channel.Id, model.PERMISSION_DELETE_PUBLIC_CHANNEL) {
 			c.SetPermissionError(model.PERMISSION_DELETE_PUBLIC_CHANNEL)
 			return
@@ -491,6 +499,7 @@ func deleteChannel(c *Context, w http.ResponseWriter, r *http.Request) {
 			c.SetPermissionError(model.PERMISSION_DELETE_PRIVATE_CHANNEL)
 			return
 		}
+	}
 
 	err = app.DeleteChannel(channel, c.Session.UserId)
 	if err != nil {

api4/channel_test.go

@@ -1006,6 +1006,16 @@ func TestDeleteChannel(t *testing.T) {
 
 	_, resp = th.SystemAdminClient.DeleteChannel(privateChannel7.Id)
 	CheckNoError(t, resp)
+
+	// last member of a channel should be able to delete it regardless of required permissions
+	publicChannel6 = th.CreateChannelWithClient(th.Client, model.CHANNEL_OPEN)
+	privateChannel7 = th.CreateChannelWithClient(th.Client, model.CHANNEL_PRIVATE)
+
+	_, resp = Client.DeleteChannel(publicChannel6.Id)
+	CheckNoError(t, resp)
+
+	_, resp = Client.DeleteChannel(privateChannel7.Id)
+	CheckNoError(t, resp)
 }
 
 func TestGetChannelByName(t *testing.T) {