Sanitize resource warheads

- Fix potential crash due to invalid target (no CenterPosition)
- Fix potential crash on multiple ResourceLayers

OpenRA.Mods.Common/Warheads/CreateResourceWarhead.cs

@@ -17,35 +17,43 @@ using OpenRA.Traits;
 
 namespace OpenRA.Mods.Common.Warheads
 {
-	public class CreateResourceWarhead : Warhead
+	public class CreateResourceWarhead : Warhead, IRulesetLoaded<WeaponInfo>
 	{
 		[Desc("Size of the area. The resources are seeded within this area.", "Provide 2 values for a ring effect (outer/inner).")]
 		public readonly int[] Size = { 0, 0 };
 
 		[Desc("Will this splatter resources and which?")]
+		[FieldLoader.Require]
 		public readonly string AddsResourceType = null;
 
+		void IRulesetLoaded<WeaponInfo>.RulesetLoaded(Ruleset rules, WeaponInfo info)
+		{
+			var world = rules.Actors["world"];
+			var resourceType = world.TraitInfos<ResourceTypeInfo>()
+				.FirstOrDefault(t => t.Type == AddsResourceType);
+
+			if (resourceType == null)
+				throw new YamlException("CreateResourceWarhead defines an invalid resource type '{0}'".F(AddsResourceType));
+		}
+
 		// TODO: Allow maximum resource splatter to be defined. (Per tile, and in total).
 		public override void DoImpact(Target target, WarheadArgs args)
 		{
-			if (string.IsNullOrEmpty(AddsResourceType))
+			if (target.Type == TargetType.Invalid)
 				return;
 
 			var firedBy = args.SourceActor;
+			var pos = target.CenterPosition;
 			var world = firedBy.World;
-			var targetTile = world.Map.CellContaining(target.CenterPosition);
-			var resLayer = world.WorldActor.Trait<ResourceLayer>();
+			var targetTile = world.Map.CellContaining(pos);
 
 			var minRange = (Size.Length > 1 && Size[1] > 0) ? Size[1] : 0;
 			var allCells = world.Map.FindTilesInAnnulus(targetTile, minRange, Size[0]);
 
 			var resourceType = world.WorldActor.TraitsImplementing<ResourceType>()
-				.FirstOrDefault(t => t.Info.Type == AddsResourceType);
+				.First(t => t.Info.Type == AddsResourceType);
 
-			if (resourceType == null)
-				Log.Write("debug", "Warhead defines an invalid resource type '{0}'".F(AddsResourceType));
-			else
-			{
+			var resLayer = world.WorldActor.Trait<ResourceLayer>();
 			foreach (var cell in allCells)
 			{
 				if (!resLayer.CanSpawnResourceAt(resourceType, cell))
@@ -56,5 +64,4 @@ namespace OpenRA.Mods.Common.Warheads
 			}
 		}
 	}
-	}
 }

OpenRA.Mods.Common/Warheads/DestroyResourceWarhead.cs

@@ -24,9 +24,13 @@ namespace OpenRA.Mods.Common.Warheads
 		// TODO: Allow maximum resource removal to be defined. (Per tile, and in total).
 		public override void DoImpact(Target target, WarheadArgs args)
 		{
+			if (target.Type == TargetType.Invalid)
+				return;
+
 			var firedBy = args.SourceActor;
+			var pos = target.CenterPosition;
 			var world = firedBy.World;
-			var targetTile = world.Map.CellContaining(target.CenterPosition);
+			var targetTile = world.Map.CellContaining(pos);
 			var resLayer = world.WorldActor.Trait<ResourceLayer>();
 
 			var minRange = (Size.Length > 1 && Size[1] > 0) ? Size[1] : 0;