Add cvar_subs command

Dumb little thing, just wanted to test something.

Resources/Locale/en-US/commands.ftl

@@ -43,6 +43,13 @@ cmd-cvar-compl-list = List available CVars
 cmd-cvar-arg-name = <name | ?>
 cmd-cvar-value-hidden = <value hidden>
 
+## 'cvar_subs' command
+cmd-cvar_subs-desc = Lists the OnValueChanged subscriptions for a CVar.
+cmd-cvar_subs-help = Usage: cvar_subs <name>
+
+cmd-cvar_subs-invalid-args = Must provide exactly one argument.
+cmd-cvar_subs-arg-name = <name>
+
 ## 'list' command
 cmd-list-desc = Lists available commands, with optional search filter
 cmd-list-help = Usage: list [filter]

Robust.Shared/Configuration/ConfigurationCommands.cs

@@ -140,4 +140,47 @@ namespace Robust.Shared.Configuration
             throw new NotSupportedException();
         }
     }
+
+    internal sealed class CVarSubsCommand : LocalizedCommands
+    {
+        [Dependency] private readonly IConfigurationManager _cfg = default!;
+
+        public override string Command => "cvar_subs";
+
+        public override void Execute(IConsoleShell shell, string argStr, string[] args)
+        {
+            if (args.Length < 1)
+            {
+                shell.WriteError(Loc.GetString("cmd-cvar_subs-invalid-args"));
+                return;
+            }
+
+            var name = args[0];
+            var subs = ((ConfigurationManager)_cfg).GetSubs(name);
+
+            foreach (var @delegate in subs)
+            {
+                shell.WriteLine(ShowDelegateInfo(@delegate));
+            }
+        }
+
+        private static string ShowDelegateInfo(Delegate del)
+        {
+            return $"{del}: {del.Method} -> {del.Target}";
+        }
+
+        public override CompletionResult GetCompletion(IConsoleShell shell, string[] args)
+        {
+            if (args.Length == 1)
+            {
+                return CompletionResult.FromHintOptions(
+                    _cfg.GetRegisteredCVars()
+                        .Select(c => new CompletionOption(c))
+                        .OrderBy(c => c.Value),
+                    Loc.GetString("cmd-cvar_subs-arg-name"));
+            }
+
+            return CompletionResult.Empty;
+        }
+    }
 }

Robust.Shared/Configuration/ConfigurationManager.cs

@@ -777,6 +777,24 @@ namespace Robust.Shared.Configuration
             return Convert.ChangeType(value, cVar);
         }
 
+        internal List<Delegate> GetSubs(string name)
+        {
+            using (Lock.ReadGuard())
+            {
+                var list = new List<Delegate>();
+
+                if (!_configVars.TryGetValue(name, out var cVar))
+                    throw new InvalidConfigurationException($"Trying to get unregistered variable '{name}'");
+
+                foreach (var entry in cVar.ValueChanged.Entries)
+                {
+                    list.Add((Delegate) entry.Equality!);
+                }
+
+                return list;
+            }
+        }
+
         /// <summary>
         ///     Holds the data for a single configuration variable.
         /// </summary>