Add a sequence reference attribute to label fallbacks.

OpenRA.Game/Traits/LintAttributes.cs

@@ -55,10 +55,12 @@ namespace OpenRA.Traits
 	{
 		public readonly string ImageReference; // The field name in the same trait info that contains the image name.
 		public readonly bool Prefix;
-		public SequenceReferenceAttribute(string imageReference = null, bool prefix = false)
+		public readonly bool ActorNameFallback;
+		public SequenceReferenceAttribute(string imageReference = null, bool prefix = false, bool actorNameFallback = false)
 		{
 			ImageReference = imageReference;
 			Prefix = prefix;
+			ActorNameFallback = actorNameFallback;
 		}
 	}
 

OpenRA.Mods.Common/Lint/CheckSequences.cs

@@ -82,6 +82,12 @@ namespace OpenRA.Mods.Common.Lint
 											{
 												if (string.IsNullOrEmpty(imageOverride))
 												{
+													if (!sequenceReference.ActorNameFallback)
+													{
+														emitWarning("Custom sprite image of actor {0} is null and there is no fallback.".F(actorInfo.Value.Name));
+														continue;
+													}
+
 													foreach (var sequenceProvider in sequenceProviders)
 													{
 														var image = renderInfo.GetImage(actorInfo.Value, sequenceProvider, faction);

OpenRA.Mods.Common/Traits/Render/WithDecoration.cs

@@ -23,7 +23,7 @@ namespace OpenRA.Mods.Common.Traits.Render
 		public readonly string Image = null;
 
 		[FieldLoader.Require]
-		[SequenceReference("Image")]
+		[SequenceReference("Image", false, true)]
 		[Desc("Sequence used for this decoration (can be animated).")]
 		public readonly string Sequence = null;
 

OpenRA.Mods.Common/Traits/Render/WithIdleOverlay.cs

@@ -23,11 +23,11 @@ namespace OpenRA.Mods.Common.Traits.Render
 		[Desc("Image used for this decoration. Defaults to the actor's type.")]
 		public readonly string Image = null;
 
-		[SequenceReference("Image")]
+		[SequenceReference("Image", false, true)]
 		[Desc("Animation to play when the actor is created.")]
 		public readonly string StartSequence = null;
 
-		[SequenceReference("Image")]
+		[SequenceReference("Image", false, true)]
 		[Desc("Sequence name to use")]
 		public readonly string Sequence = "idle-overlay";