[OneBot] Fix ForwardEntity cannot be serialized (#824)

Author: DarkRRb

Lagrange.OneBot/Database/MessageChainFormatter.cs

@@ -0,0 +1,19 @@
+using Lagrange.Core.Message;
+using Lagrange.Core.Message.Entity;
+using MessagePack;
+using MessagePack.Formatters;
+
+namespace Lagrange.OneBot.Database;
+
+public class MessageChainFormatter : IMessagePackFormatter<MessageChain?>
+{
+    public MessageChain? Deserialize(ref MessagePackReader reader, MessagePackSerializerOptions options)
+    {
+        return MessagePackSerializer.Deserialize<MessageRecord>(ref reader, options);
+    }
+
+    public void Serialize(ref MessagePackWriter writer, MessageChain? value, MessagePackSerializerOptions options)
+    {
+        MessagePackSerializer.Serialize(ref writer, (MessageRecord?)value, options);
+    }
+}

Lagrange.OneBot/Database/MessageEntityResolver.cs

@@ -6,11 +6,15 @@ namespace Lagrange.OneBot.Database;
 
 public class MessageEntityResolver : IFormatterResolver
 {
-    private static readonly MessageEntityFormatter _FORMATTER = new();
+    private static readonly MessageEntityFormatter ENTITY_FORMATTER = new();
+
+    private static readonly MessageChainFormatter CHAIN_FORMATTER = new();
 
     public IMessagePackFormatter<T>? GetFormatter<T>()
     {
-        if (typeof(T) == typeof(IMessageEntity)) return (IMessagePackFormatter<T>?)_FORMATTER;
+        if (typeof(T) == typeof(IMessageEntity)) return (IMessagePackFormatter<T>)ENTITY_FORMATTER;
+
+        if (typeof(T) == typeof(MessageChain)) return (IMessagePackFormatter<T>)CHAIN_FORMATTER;
 
         return null;
     }

Lagrange.OneBot/Database/MessageRecord.cs

@@ -30,8 +30,8 @@ public partial class MessageRecord : IRealmObject
 {
     public static readonly MessagePackSerializerOptions OPTIONS = MessagePackSerializerOptions.Standard
         .WithResolver(CompositeResolver.Create(
-            ContractlessStandardResolver.Instance,
-            new MessageEntityResolver()
+            new MessageEntityResolver(),
+            ContractlessStandardResolver.Instance
         ));
 
     [PrimaryKey]
@@ -72,7 +72,7 @@ public static int CalcMessageHash(ulong msgId, uint seq)
         return ((ushort)seq << 16) | (ushort)msgId;
     }
 
-    public static implicit operator MessageRecord(MessageChain chain) => new()
+    public static implicit operator MessageRecord?(MessageChain? chain) => chain == null ? null : new()
     {
         Id = CalcMessageHash(chain.MessageId, chain.Sequence),
         Type = chain.Type,
@@ -92,8 +92,10 @@ MessageType.Temp or
         Entities = MessagePackSerializer.Serialize<List<IMessageEntity>>(chain, OPTIONS)
     };
 
-    public static implicit operator MessageChain(MessageRecord record)
+    public static implicit operator MessageChain?(MessageRecord? record)
     {
+        if (record == null) return null;
+
         var chain = record.Type switch
         {
             MessageType.Group => new MessageChain(