Deserialize mod rules only once when loading all maps.

This avoids loading, parsing and merging YAML rules for the mod during loading of each individual map. This saves significant time resolving custom rules on each map loaded.

OpenRA.Game/Map/MapCache.cs

@@ -123,10 +123,12 @@ namespace OpenRA
 				mapDirectoryTrackers.Add(new MapDirectoryTracker(mapGrid, package, classification));
 			}
 
+			// PERF: Load the mod YAML once outside the loop, and reuse it when resolving each maps custom YAML.
+			var modDataRules = modData.GetRulesYaml();
 			foreach (var kv in MapLocations)
 			{
 				foreach (var map in kv.Key.Contents)
-					LoadMap(map, kv.Key, kv.Value, mapGrid, null);
+					LoadMapInternal(map, kv.Key, kv.Value, mapGrid, null, modDataRules);
 			}
 
 			// We only want to track maps in runtime, not at loadtime
@@ -134,6 +136,11 @@ namespace OpenRA
 		}
 
 		public void LoadMap(string map, IReadOnlyPackage package, MapClassification classification, MapGrid mapGrid, string oldMap)
+		{
+			LoadMapInternal(map, package, classification, mapGrid, oldMap, null);
+		}
+
+		void LoadMapInternal(string map, IReadOnlyPackage package, MapClassification classification, MapGrid mapGrid, string oldMap, IEnumerable<List<MiniYamlNode>> modDataRules)
 		{
 			IReadOnlyPackage mapPackage = null;
 			try
@@ -144,7 +151,7 @@ namespace OpenRA
 					if (mapPackage != null)
 					{
 						var uid = Map.ComputeUID(mapPackage);
-						previews[uid].UpdateFromMap(mapPackage, package, classification, modData.Manifest.MapCompatibility, mapGrid.Type);
+						previews[uid].UpdateFromMap(mapPackage, package, classification, modData.Manifest.MapCompatibility, mapGrid.Type, modDataRules);
 
 						if (oldMap != uid)
 						{

OpenRA.Game/Map/MapPreview.cs

@@ -111,7 +111,7 @@ namespace OpenRA
 				return key == "world" || key == "player";
 			}
 
-			public void SetCustomRules(ModData modData, IReadOnlyFileSystem fileSystem, Dictionary<string, MiniYaml> yaml)
+			public void SetCustomRules(ModData modData, IReadOnlyFileSystem fileSystem, Dictionary<string, MiniYaml> yaml, IEnumerable<List<MiniYamlNode>> modDataRules)
 			{
 				RuleDefinitions = LoadRuleSection(yaml, "Rules");
 				WeaponDefinitions = LoadRuleSection(yaml, "Weapons");
@@ -131,14 +131,17 @@ namespace OpenRA
 					// This assumes/enforces that these actor types can only inherit abstract definitions (starting with ^)
 					if (RuleDefinitions != null)
 					{
-						var files = modData.Manifest.Rules.AsEnumerable();
+						modDataRules ??= modData.GetRulesYaml();
+						var files = Enumerable.Empty<string>();
 						if (RuleDefinitions.Value != null)
 						{
 							var mapFiles = FieldLoader.GetValue<string[]>("value", RuleDefinitions.Value);
 							files = files.Append(mapFiles);
 						}
 
-						var sources = files.Select(s => MiniYaml.FromStream(fileSystem.Open(s), s).Where(IsLoadableRuleDefinition).ToList());
+						var sources =
+							modDataRules.Select(x => x.Where(IsLoadableRuleDefinition).ToList())
+							.Concat(files.Select(s => MiniYaml.FromStream(fileSystem.Open(s), s).Where(IsLoadableRuleDefinition).ToList()));
 						if (RuleDefinitions.Nodes.Count > 0)
 							sources = sources.Append(RuleDefinitions.Nodes.Where(IsLoadableRuleDefinition).ToList());
 
@@ -319,10 +322,10 @@ namespace OpenRA
 				{ "Notifications", map.NotificationDefinitions },
 				{ "Sequences", map.SequenceDefinitions },
 				{ "ModelSequences", map.ModelSequenceDefinitions }
-			});
+			}, null);
 		}
 
-		public void UpdateFromMap(IReadOnlyPackage p, IReadOnlyPackage parent, MapClassification classification, string[] mapCompatibility, MapGridType gridType)
+		public void UpdateFromMap(IReadOnlyPackage p, IReadOnlyPackage parent, MapClassification classification, string[] mapCompatibility, MapGridType gridType, IEnumerable<List<MiniYamlNode>> modDataRules)
 		{
 			Dictionary<string, MiniYaml> yaml;
 			using (var yamlStream = p.GetStream("map.yaml"))
@@ -412,7 +415,7 @@ namespace OpenRA
 				newData.Status = MapStatus.Unavailable;
 			}
 
-			newData.SetCustomRules(modData, this, yaml);
+			newData.SetCustomRules(modData, this, yaml, modDataRules);
 
 			if (cache.LoadPreviewImages && p.Contains("map.png"))
 				using (var dataStream = p.GetStream("map.png"))
@@ -475,7 +478,7 @@ namespace OpenRA
 
 					var rulesString = Encoding.UTF8.GetString(Convert.FromBase64String(r.rules));
 					var rulesYaml = new MiniYaml("", MiniYaml.FromString(rulesString)).ToDictionary();
-					newData.SetCustomRules(modData, this, rulesYaml);
+					newData.SetCustomRules(modData, this, rulesYaml, null);
 				}
 				catch (Exception e)
 				{
@@ -554,7 +557,7 @@ namespace OpenRA
 						innerData.Status = MapStatus.DownloadError;
 					else
 					{
-						UpdateFromMap(package, mapInstallPackage, MapClassification.User, null, GridType);
+						UpdateFromMap(package, mapInstallPackage, MapClassification.User, null, GridType, null);
 						Game.RunAfterTick(onSuccess);
 					}
 				}

OpenRA.Game/ModData.cs

@@ -166,6 +166,11 @@ namespace OpenRA
 			return map;
 		}
 
+		public List<MiniYamlNode>[] GetRulesYaml()
+		{
+			return Manifest.Rules.Select(s => MiniYaml.FromStream(DefaultFileSystem.Open(s), s)).ToArray();
+		}
+
 		public void Dispose()
 		{
 			LoadScreen?.Dispose();