Add --check-conditional-trait-interface-overrides utility command.

This command is used by `make check` to detect traits that incorrectly
override interface methods that are required for conditions to work
correctly.

OpenRA.Mods.Common/UtilityCommands/CheckConditionalTraitInterfaceOverrides.cs

@@ -0,0 +1,77 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2019 The OpenRA Developers (see AUTHORS)
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System;
+using System.Linq;
+using System.Reflection;
+using OpenRA.Mods.Common.Traits;
+using OpenRA.Traits;
+
+namespace OpenRA.Mods.Common.UtilityCommands
+{
+	public class CheckConditionalTraitInterfaceOverrides : IUtilityCommand
+	{
+		string IUtilityCommand.Name { get { return "--check-conditional-trait-interface-overrides"; } }
+
+		bool IUtilityCommand.ValidateArguments(string[] args)
+		{
+			return args.Length == 1;
+		}
+
+		int violationCount;
+
+		static bool IsConditionalTrait(Type type)
+		{
+			// Walk up the inheritance chain to check if any parent type is the generic ConditionalTrait type
+			while (type != null && type != typeof(object))
+			{
+				if (type.IsGenericType && type.GetGenericTypeDefinition() == typeof(ConditionalTrait<>))
+					return true;
+
+				type = type.BaseType;
+			}
+
+			return false;
+		}
+
+		void CheckInterfaceViolation(Utility utility, Type interfaceType, string methodName)
+		{
+			var types = utility.ModData.ObjectCreator.GetTypes()
+				.Where(t => interfaceType.IsAssignableFrom(t) && !t.IsGenericType);
+
+			foreach (var t in types)
+			{
+				if (!IsConditionalTrait(t))
+					continue;
+
+				var overridesCreated = t.GetMethod("{0}.{1}".F(interfaceType.FullName, methodName), BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.DeclaredOnly) != null;
+				if (overridesCreated)
+				{
+					Console.WriteLine("{0} must override ConditionalTrait's {1} method instead of implementing {2} directly", t.Name, methodName, interfaceType.Name);
+					violationCount++;
+				}
+			}
+		}
+
+		[Desc("Check for incorrect interface overrides in conditional traits defined in all assemblies referenced by the specified mod.")]
+		void IUtilityCommand.Run(Utility utility, string[] args)
+		{
+			CheckInterfaceViolation(utility, typeof(INotifyCreated), "Created");
+			CheckInterfaceViolation(utility, typeof(IObservesVariables), "GetVariableObservers");
+
+			if (violationCount > 0)
+			{
+				Console.WriteLine("Interface override violations: {0}", violationCount);
+				Environment.Exit(1);
+			}
+		}
+	}
+}