Don't throw an exception when a field is missing

OpenRA.Game/GameRules/ActorInfo.cs

@@ -44,7 +44,11 @@ namespace OpenRA
 				{
 					try
 					{
-						traits.Add(LoadTraitInfo(creator, t.Key.Split('@')[0], t.Value));
+						// HACK: The linter does not want to crash when a trait doesn't exist but only print an error instead
+						// LoadTraitInfo will only return null to signal us to abort here if the linter is running
+						var trait = LoadTraitInfo(creator, t.Key.Split('@')[0], t.Value);
+						if (trait != null)
+							traits.Add(trait);
 					}
 					catch (FieldLoader.MissingFieldsException e)
 					{
@@ -73,7 +77,13 @@ namespace OpenRA
 			if (!string.IsNullOrEmpty(my.Value))
 				throw new YamlException("Junk value `{0}` on trait node {1}"
 				.F(my.Value, traitName));
+
+			// HACK: The linter does not want to crash when a trait doesn't exist but only print an error instead
+			// ObjectCreator will only return null to signal us to abort here if the linter is running
 			var info = creator.CreateObject<ITraitInfo>(traitName + "Info");
+			if (info == null)
+				return null;
+
 			try
 			{
 				FieldLoader.Load(info, my);

OpenRA.Game/ObjectCreator.cs

@@ -74,8 +74,8 @@ namespace OpenRA
 			return assemblies.Select(a => a.First).FirstOrDefault(a => a.FullName == e.Name);
 		}
 
-		public static Action<string> MissingTypeAction =
+		// Only used by the linter to prevent exceptions from being thrown during a lint run
-			s => { throw new InvalidOperationException("Cannot locate type: {0}".F(s)); };
+		public static Action<string> MissingTypeAction = null;
 
 		public T CreateObject<T>(string className)
 		{
@@ -87,7 +87,12 @@ namespace OpenRA
 			var type = typeCache[className];
 			if (type == null)
 			{
+				// HACK: The linter does not want to crash but only print an error instead
+				if (MissingTypeAction != null)
 					MissingTypeAction(className);
+				else
+					throw new InvalidOperationException("Cannot locate type: {0}".F(className));
+
 				return default(T);
 			}