implement "pubsub numsub"; fix glitch in command tree (impacts "command" and...

implement "pubsub numsub"; fix glitch in command tree (impacts "command" and "command info" - gave nil name)

toys/StackExchange.Redis.Server/RedisServer.cs

@@ -576,6 +576,15 @@ protected virtual TypedRedisValue Publish(RedisClient client, RedisRequest reque
             return TypedRedisValue.Integer(count);
         }
 
+        [RedisCommand(-3, "pubsub", "numsub", LockFree = true)]
+        protected virtual TypedRedisValue PubsubNumsub(RedisClient client, RedisRequest request)
+        {
+            var channel = request.GetChannel(2, RedisChannel.PatternMode.Literal);
+            var subscribers = FilterSubscribers(channel);
+            int count = subscribers.Count;
+            if (count != 0) ArrayPool<RedisClient>.Shared.Return(subscribers.Array);
+            return TypedRedisValue.Integer(count);
+        }
 
 
         [RedisCommand(1, LockFree = true)]

toys/StackExchange.Redis.Server/RespServer.cs

@@ -52,7 +52,9 @@ RedisCommandAttribute CheckSignatureAndGetAttribute(MethodInfo method)
                 if (grp.Any(x => x.IsSubCommand))
                 {
                     var subs = grp.Where(x => x.IsSubCommand).ToArray();
-                    parent = grp.SingleOrDefault(x => !x.IsSubCommand).WithSubCommands(subs);
+                    parent = grp.SingleOrDefault(x => !x.IsSubCommand);
+                    if (parent.Command == null) parent = new RespCommand(subs[0].Command);
+                    parent = parent.WithSubCommands(subs);
                 }
                 else
                 {
@@ -137,6 +139,13 @@ private RespCommand(RespCommand parent, RespCommand[] subs)
                 _operation = parent._operation;
                 _subcommands = subs;
             }
+
+            internal RespCommand(string command) : this()
+            {
+                Command = command;
+                Arity = -1;
+                MaxArgs = int.MaxValue;
+            }
             public bool IsUnknown => _operation == null;
             public RespCommand Resolve(in RedisRequest request)
             {