Fire Message events and enable GetMessage even if cache is disabled. Add Message.User null checks.

src/Discord.Net/DiscordClient.cs

@@ -858,45 +858,33 @@ namespace Discord
                         break;
                     case "MESSAGE_UPDATE":
                         {
-                            if (Config.MessageCacheSize > 0)
+                            var data = e.Payload.ToObject<MessageUpdateEvent>(_serializer);
+                            var channel = GetChannel(data.ChannelId);
+                            if (channel != null)
                             {
-                                var data = e.Payload.ToObject<MessageUpdateEvent>(_serializer);
-                                var channel = GetChannel(data.ChannelId);
-                                if (channel != null)
-                                {
-                                    var msg = channel.GetMessage(data.Id);
-                                    if (msg != null)
-                                    {
-                                        msg.Update(data);
-                                        if (Config.LogEvents)
-                                            Logger.Info($"Message Update: {channel.Server?.Name ?? "[Private]"}/{channel.Name}");
-                                        OnMessageUpdated(msg);
-                                    }
-                                }
-                                else
-                                    Logger.Warning("MESSAGE_UPDATE referenced an unknown channel.");
+                                var msg = channel.GetMessage(data.Id, data.Author.Id);
+                                msg.Update(data);
+                                if (Config.LogEvents)
+                                    Logger.Info($"Message Update: {channel.Server?.Name ?? "[Private]"}/{channel.Name}");
+                                OnMessageUpdated(msg);
                             }
+                            else
+                                Logger.Warning("MESSAGE_UPDATE referenced an unknown channel.");
                         }
                         break;
                     case "MESSAGE_DELETE":
                         {
-                            if (Config.MessageCacheSize > 0)
+                            var data = e.Payload.ToObject<MessageDeleteEvent>(_serializer);
+                            var channel = GetChannel(data.ChannelId);
+                            if (channel != null)
                             {
-                                var data = e.Payload.ToObject<MessageDeleteEvent>(_serializer);
-                                var channel = GetChannel(data.ChannelId);
-                                if (channel != null)
-                                {
-                                    var msg = channel.RemoveMessage(data.Id);
-                                    if (msg != null)
-                                    {
-                                        if (Config.LogEvents)
-                                            Logger.Info($"Message Deleted: {channel.Server?.Name ?? "[Private]"}/{channel.Name}");
-                                        OnMessageDeleted(msg);
-                                    }
-                                }
-                                else
-                                    Logger.Warning("MESSAGE_DELETE referenced an unknown channel.");
+                                var msg = channel.RemoveMessage(data.Id);
+                                if (Config.LogEvents)
+                                    Logger.Info($"Message Deleted: {channel.Server?.Name ?? "[Private]"}/{channel.Name}");
+                                OnMessageDeleted(msg);
                             }
+                            else
+                                Logger.Warning("MESSAGE_DELETE referenced an unknown channel.");
                         }
                         break;
                     case "MESSAGE_ACK":
@@ -907,7 +895,7 @@ namespace Discord
                                 var channel = GetChannel(data.ChannelId);
                                 if (channel != null)
                                 {
-                                    var msg = channel.GetMessage(data.MessageId);
+                                    var msg = channel.GetMessage(data.MessageId, null);
                                     if (msg != null)
                                     {
                                         if (Config.LogEvents)

src/Discord.Net/Models/Channel.cs

@@ -263,21 +263,25 @@ namespace Discord
             if (Client.Config.MessageCacheSize > 0)
             {
                 Message msg;
-                _messages.TryRemove(id, out msg);
-                return msg;
+                if (_messages.TryRemove(id, out msg))
+                    return msg;
             }
-            return null;
+            return new Message(id, this, null);
         }
 
         public Message GetMessage(ulong id)
+            => GetMessage(id, null);
+        internal Message GetMessage(ulong id, ulong? userId)
         {
-            if (Client.Config.MessageCacheSize <= 0)
-                throw new InvalidOperationException("Unable to retrieve a message when the message cache is disabled.");
-
-            Message result;
-            _messages.TryGetValue(id, out result);
-            return result;
+            if (Client.Config.MessageCacheSize > 0)
+            {
+                Message result;
+                if (_messages.TryGetValue(id, out result))
+                    return result;
+            }
+            return new Message(id, this, userId != null ? GetUser(userId.Value) : null);
         }
+
         public async Task<Message[]> DownloadMessages(int limit = 100, ulong? relativeMessageId = null, 
             RelativeDirection relativeDir = RelativeDirection.Before, bool useCache = true)
         {

src/Discord.Net/Models/Message.cs

@@ -206,7 +206,7 @@ namespace Discord
         /// <summary> Returns the server containing the channel this message was sent to. </summary>
         public Server Server => Channel.Server;
         /// <summary> Returns if this message was sent from the logged-in accounts. </summary>
-        public bool IsAuthor => User.Id == Client.CurrentUser?.Id;
+        public bool IsAuthor => User != null && User.Id == Client.CurrentUser?.Id;
 
 		internal Message(ulong id, Channel channel, User user)
 		{
@@ -279,7 +279,7 @@ namespace Discord
 			}
 			if (model.IsMentioningEveryone != null)
 			{
-				if (model.IsMentioningEveryone.Value && User.GetPermissions(channel).MentionEveryone)
+				if (model.IsMentioningEveryone.Value && User != null && User.GetPermissions(channel).MentionEveryone)
 					MentionedRoles = new Role[] { Server.EveryoneRole };
 				else
 					MentionedRoles = new Role[0];
@@ -360,6 +360,6 @@ namespace Discord
 
         public override bool Equals(object obj) => obj is Message && (obj as Message).Id == Id;
 		public override int GetHashCode() => unchecked(Id.GetHashCode() + 9979);
-		public override string ToString() => $"{User}: {RawText}";
+		public override string ToString() => $"{User?.Name ?? "Unknown User"}: {RawText}";
 	}
 }