Improve lookups of nodes by key in MiniYaml.

When handling the Nodes collection in MiniYaml, individual nodes are located via one of two methods:

// Lookup a single key with linear search.
var node = yaml.Nodes.FirstOrDefault(n => n.Key == "SomeKey");

// Convert to dictionary, expecting many key lookups.
var dict = nodes.ToDictionary();

// Lookup a single key in the dictionary.
var node = dict["SomeKey"];

To simplify lookup of individual keys via linear search, provide helper methods NodeWithKeyOrDefault and NodeWithKey. These helpers do the equivalent of Single{OrDefault} searches. Whilst this requires checking the whole list, it provides a useful correctness check. Two duplicated keys in TS yaml are fixed as a result. We can also optimize the helpers to not use LINQ, avoiding allocation of the delegate to search for a key.

Adjust existing code to use either lnear searches or dictionary lookups based on whether it will be resolving many keys. Resolving few keys can be done with linear searches to avoid building a dictionary. Resolving many keys should be done with a dictionary to avoid quaradtic runtime from repeated linear searches.

OpenRA.Game/ExternalMods.cs

@@ -94,17 +94,17 @@ void LoadMod(MiniYaml yaml, string path = null, bool forceRegistration = false)
 
 			if (sheetBuilder != null)
 			{
-				var iconNode = yaml.Nodes.FirstOrDefault(n => n.Key == "Icon");
+				var iconNode = yaml.NodeWithKeyOrDefault("Icon");
 				if (iconNode != null && !string.IsNullOrEmpty(iconNode.Value.Value))
 					using (var stream = new MemoryStream(Convert.FromBase64String(iconNode.Value.Value)))
 						mod.Icon = sheetBuilder.Add(new Png(stream));
 
-				var icon2xNode = yaml.Nodes.FirstOrDefault(n => n.Key == "Icon2x");
+				var icon2xNode = yaml.NodeWithKeyOrDefault("Icon2x");
 				if (icon2xNode != null && !string.IsNullOrEmpty(icon2xNode.Value.Value))
 					using (var stream = new MemoryStream(Convert.FromBase64String(icon2xNode.Value.Value)))
 						mod.Icon2x = sheetBuilder.Add(new Png(stream), 1f / 2);
 
-				var icon3xNode = yaml.Nodes.FirstOrDefault(n => n.Key == "Icon3x");
+				var icon3xNode = yaml.NodeWithKeyOrDefault("Icon3x");
 				if (icon3xNode != null && !string.IsNullOrEmpty(icon3xNode.Value.Value))
 					using (var stream = new MemoryStream(Convert.FromBase64String(icon3xNode.Value.Value)))
 						mod.Icon3x = sheetBuilder.Add(new Png(stream), 1f / 3);

OpenRA.Game/GameRules/SoundInfo.cs

@@ -44,12 +44,12 @@ public SoundInfo(MiniYaml y)
 			foreach (var t in classifiction.Value.Nodes)
 			{
 				var volumeModifier = 1f;
-				var volumeModifierNode = t.Value.Nodes.FirstOrDefault(x => x.Key == nameof(SoundPool.VolumeModifier));
+				var volumeModifierNode = t.Value.NodeWithKeyOrDefault(nameof(SoundPool.VolumeModifier));
 				if (volumeModifierNode != null)
 					volumeModifier = FieldLoader.GetValue<float>(volumeModifierNode.Key, volumeModifierNode.Value.Value);
 
 				var interruptType = SoundPool.DefaultInterruptType;
-				var interruptTypeNode = t.Value.Nodes.FirstOrDefault(x => x.Key == nameof(SoundPool.InterruptType));
+				var interruptTypeNode = t.Value.NodeWithKeyOrDefault(nameof(SoundPool.InterruptType));
 				if (interruptTypeNode != null)
 					interruptType = FieldLoader.GetValue<SoundPool.InterruptType>(interruptTypeNode.Key, interruptTypeNode.Value.Value);
 

OpenRA.Game/GameRules/WeaponInfo.cs

@@ -145,7 +145,8 @@ public WeaponInfo(MiniYaml content)
 
 		static object LoadProjectile(MiniYaml yaml)
 		{
-			if (!yaml.ToDictionary().TryGetValue("Projectile", out var proj))
+			var proj = yaml.NodeWithKeyOrDefault("Projectile")?.Value;
+			if (proj == null)
 				return null;
 
 			var ret = Game.CreateObject<IProjectileInfo>(proj.Value + "Info");

OpenRA.Game/GameSpeed.cs

@@ -10,7 +10,6 @@
 #endregion
 
 using System.Collections.Generic;
-using System.Linq;
 
 namespace OpenRA
 {
@@ -38,7 +37,7 @@ public class GameSpeeds : IGlobalModData
 		static object LoadSpeeds(MiniYaml y)
 		{
 			var ret = new Dictionary<string, GameSpeed>();
-			var speedsNode = y.Nodes.FirstOrDefault(n => n.Key == "Speeds");
+			var speedsNode = y.NodeWithKeyOrDefault("Speeds");
 			if (speedsNode == null)
 				throw new YamlException("Error parsing GameSpeeds: Missing Speeds node!");
 

OpenRA.Game/Graphics/CursorProvider.cs

@@ -27,22 +27,22 @@ public CursorProvider(ModData modData)
 			var sequenceYaml = MiniYaml.Merge(modData.Manifest.Cursors.Select(
 				s => MiniYaml.FromStream(fileSystem.Open(s), s)));
 
-			var nodesDict = new MiniYaml(null, sequenceYaml).ToDictionary();
+			var cursorsYaml = new MiniYaml(null, sequenceYaml).NodeWithKey("Cursors").Value;
 
 			// Overwrite previous definitions if there are duplicates
 			var pals = new Dictionary<string, IProvidesCursorPaletteInfo>();
 			foreach (var p in modData.DefaultRules.Actors[SystemActors.World].TraitInfos<IProvidesCursorPaletteInfo>())
 				if (p.Palette != null)
 					pals[p.Palette] = p;
 
-			Palettes = nodesDict["Cursors"].Nodes.Select(n => n.Value.Value)
+			Palettes = cursorsYaml.Nodes.Select(n => n.Value.Value)
 				.Where(p => p != null)
 				.Distinct()
 				.ToDictionary(p => p, p => pals[p].ReadPalette(modData.DefaultFileSystem));
 
 			var frameCache = new FrameCache(fileSystem, modData.SpriteLoaders);
 			var cursors = new Dictionary<string, CursorSequence>();
-			foreach (var s in nodesDict["Cursors"].Nodes)
+			foreach (var s in cursorsYaml.Nodes)
 				foreach (var sequence in s.Value.Nodes)
 					cursors.Add(sequence.Key, new CursorSequence(frameCache, sequence.Key, s.Key, s.Value.Value, sequence.Value));
 

OpenRA.Game/HotkeyDefinition.cs

@@ -10,7 +10,6 @@
 #endregion
 
 using System.Collections.Generic;
-using System.Linq;
 
 namespace OpenRA
 {
@@ -31,29 +30,26 @@ public HotkeyDefinition(string name, MiniYaml node)
 			if (!string.IsNullOrEmpty(node.Value))
 				Default = FieldLoader.GetValue<Hotkey>("value", node.Value);
 
-			var descriptionNode = node.Nodes.FirstOrDefault(n => n.Key == "Description");
-			if (descriptionNode != null)
-				Description = descriptionNode.Value.Value;
+			var nodeDict = node.ToDictionary();
 
-			var typesNode = node.Nodes.FirstOrDefault(n => n.Key == "Types");
-			if (typesNode != null)
-				Types = FieldLoader.GetValue<HashSet<string>>("Types", typesNode.Value.Value);
+			if (nodeDict.TryGetValue("Description", out var descriptionYaml))
+				Description = descriptionYaml.Value;
 
-			var contextsNode = node.Nodes.FirstOrDefault(n => n.Key == "Contexts");
-			if (contextsNode != null)
-				Contexts = FieldLoader.GetValue<HashSet<string>>("Contexts", contextsNode.Value.Value);
+			if (nodeDict.TryGetValue("Types", out var typesYaml))
+				Types = FieldLoader.GetValue<HashSet<string>>("Types", typesYaml.Value);
 
-			var platformNode = node.Nodes.FirstOrDefault(n => n.Key == "Platform");
-			if (platformNode != null)
+			if (nodeDict.TryGetValue("Contexts", out var contextYaml))
+				Contexts = FieldLoader.GetValue<HashSet<string>>("Contexts", contextYaml.Value);
+
+			if (nodeDict.TryGetValue("Platform", out var platformYaml))
 			{
-				var platformOverride = platformNode.Value.Nodes.FirstOrDefault(n => n.Key == Platform.CurrentPlatform.ToString());
+				var platformOverride = platformYaml.NodeWithKeyOrDefault(Platform.CurrentPlatform.ToString());
 				if (platformOverride != null)
 					Default = FieldLoader.GetValue<Hotkey>("value", platformOverride.Value.Value);
 			}
 
-			var readonlyNode = node.Nodes.FirstOrDefault(n => n.Key == "Readonly");
-			if (readonlyNode != null)
-				Readonly = FieldLoader.GetValue<bool>("Readonly", readonlyNode.Value.Value);
+			if (nodeDict.TryGetValue("Readonly", out var readonlyYaml))
+				Readonly = FieldLoader.GetValue<bool>("Readonly", readonlyYaml.Value);
 		}
 	}
 }

OpenRA.Game/Manifest.cs

@@ -214,7 +214,7 @@ static string[] YamlList(Dictionary<string, MiniYaml> yaml, string key)
 			if (!yaml.ContainsKey(key))
 				return Array.Empty<string>();
 
-			return yaml[key].ToDictionary().Keys.ToArray();
+			return yaml[key].Nodes.Select(n => n.Key).ToArray();
 		}
 
 		static IReadOnlyDictionary<string, string> YamlDictionary(Dictionary<string, MiniYaml> yaml, string key)

OpenRA.Game/Map/Map.cs

@@ -95,9 +95,9 @@ public MapField(string key, string fieldName = null, bool required = true, strin
 				t == typeof(MiniYaml) ? Type.MiniYaml : Type.Normal;
 		}
 
-		public void Deserialize(Map map, ImmutableArray<MiniYamlNode> nodes)
+		public void Deserialize(Map map, MiniYaml yaml)
 		{
-			var node = nodes.FirstOrDefault(n => n.Key == key);
+			var node = yaml.NodeWithKeyOrDefault(key);
 			if (node == null)
 			{
 				if (required)
@@ -363,13 +363,13 @@ public Map(ModData modData, IReadOnlyPackage package)
 
 			var yaml = new MiniYaml(null, MiniYaml.FromStream(Package.GetStream("map.yaml"), package.Name));
 			foreach (var field in YamlFields)
-				field.Deserialize(this, yaml.Nodes);
+				field.Deserialize(this, yaml);
 
 			if (MapFormat < SupportedMapFormat)
 				throw new InvalidDataException($"Map format {MapFormat} is not supported.\n File: {package.Name}");
 
-			PlayerDefinitions = MiniYaml.NodesOrEmpty(yaml, "Players");
-			ActorDefinitions = MiniYaml.NodesOrEmpty(yaml, "Actors");
+			PlayerDefinitions = yaml.NodeWithKeyOrDefault("Players")?.Value.Nodes ?? ImmutableArray<MiniYamlNode>.Empty;
+			ActorDefinitions = yaml.NodeWithKeyOrDefault("Actors")?.Value.Nodes ?? ImmutableArray<MiniYamlNode>.Empty;
 
 			Grid = modData.Manifest.Get<MapGrid>();
 

OpenRA.Game/MiniYaml.cs

@@ -141,6 +141,34 @@ public MiniYaml WithNodesAppended(IEnumerable<MiniYamlNode> nodes)
 			return new MiniYaml(Value, newNodes);
 		}
 
+		public MiniYamlNode NodeWithKey(string key)
+		{
+			var result = NodeWithKeyOrDefault(key);
+			if (result == null)
+				throw new InvalidDataException($"No node with key '{key}'");
+			return result;
+		}
+
+		public MiniYamlNode NodeWithKeyOrDefault(string key)
+		{
+			// PERF: Avoid LINQ.
+			var first = true;
+			MiniYamlNode result = null;
+			foreach (var node in Nodes)
+			{
+				if (node.Key != key)
+					continue;
+
+				if (!first)
+					throw new InvalidDataException($"Duplicate key '{node.Key}' in {node.Location}");
+
+				first = false;
+				result = node;
+			}
+
+			return result;
+		}
+
 		public Dictionary<string, MiniYaml> ToDictionary()
 		{
 			return ToDictionary(MiniYamlIdentity);
@@ -175,11 +203,6 @@ public MiniYaml(string value, IEnumerable<MiniYamlNode> nodes)
 			Nodes = ImmutableArray.CreateRange(nodes);
 		}
 
-		public static ImmutableArray<MiniYamlNode> NodesOrEmpty(MiniYaml y, string s)
-		{
-			return y.Nodes.FirstOrDefault(n => n.Key == s)?.Value.Nodes ?? ImmutableArray<MiniYamlNode>.Empty;
-		}
-
 		static List<MiniYamlNode> FromLines(IEnumerable<ReadOnlyMemory<char>> lines, string filename, bool discardCommentsAndWhitespace, Dictionary<string, string> stringPool)
 		{
 			stringPool ??= new Dictionary<string, string>();
@@ -668,6 +691,11 @@ yield return (hasKey ? key + ":" : "")
 				foreach (var line in Nodes.ToLines())
 					yield return "\t" + line;
 		}
+
+		public MiniYamlNodeBuilder NodeWithKeyOrDefault(string key)
+		{
+			return Nodes.SingleOrDefault(n => n.Key == key);
+		}
 	}
 
 	[Serializable]

OpenRA.Game/Network/GameServer.cs

@@ -140,7 +140,7 @@ public class GameServer
 		static object LoadClients(MiniYaml yaml)
 		{
 			var clients = new List<GameClient>();
-			var clientsNode = yaml.Nodes.FirstOrDefault(n => n.Key == "Clients");
+			var clientsNode = yaml.NodeWithKeyOrDefault("Clients");
 			if (clientsNode != null)
 			{
 				var regex = new Regex(@"Client@\d+");
@@ -159,7 +159,7 @@ public GameServer(MiniYaml yaml)
 			// Games advertised using the old API used a single Mods field
 			if (Mod == null || Version == null)
 			{
-				var modsNode = yaml.Nodes.FirstOrDefault(n => n.Key == "Mods");
+				var modsNode = yaml.NodeWithKeyOrDefault("Mods");
 				if (modsNode != null)
 				{
 					var modVersion = modsNode.Value.Value.Split('@');

OpenRA.Game/Network/LocalizedMessage.cs

@@ -60,7 +60,7 @@ public class LocalizedMessage
 		static object LoadArguments(MiniYaml yaml)
 		{
 			var arguments = new Dictionary<string, object>();
-			var argumentsNode = yaml.Nodes.FirstOrDefault(n => n.Key == "Arguments");
+			var argumentsNode = yaml.NodeWithKeyOrDefault("Arguments");
 			if (argumentsNode != null)
 			{
 				foreach (var argumentNode in argumentsNode.Value.Nodes)

OpenRA.Game/Network/Session.cs

@@ -227,7 +227,7 @@ public static Global Deserialize(MiniYaml data)
 			{
 				var gs = FieldLoader.Load<Global>(data);
 
-				var optionsNode = data.Nodes.FirstOrDefault(n => n.Key == "Options");
+				var optionsNode = data.NodeWithKeyOrDefault("Options");
 				if (optionsNode != null)
 					foreach (var n in optionsNode.Value.Nodes)
 						gs.LobbyOptions[n.Key] = FieldLoader.Load<LobbyOptionState>(n.Value);

OpenRA.Game/PlayerDatabase.cs

@@ -9,7 +9,6 @@
  */
 #endregion
 
-using System.Linq;
 using System.Threading.Tasks;
 using OpenRA.FileFormats;
 using OpenRA.Graphics;
@@ -94,10 +93,10 @@ public PlayerBadge LoadBadge(MiniYaml yaml)
 				});
 			}
 
-			var labelNode = yaml.Nodes.FirstOrDefault(n => n.Key == "Label");
-			var icon24Node = yaml.Nodes.FirstOrDefault(n => n.Key == "Icon24");
-			var icon48Node = yaml.Nodes.FirstOrDefault(n => n.Key == "Icon48");
-			var icon72Node = yaml.Nodes.FirstOrDefault(n => n.Key == "Icon72");
+			var labelNode = yaml.NodeWithKeyOrDefault("Label");
+			var icon24Node = yaml.NodeWithKeyOrDefault("Icon24");
+			var icon48Node = yaml.NodeWithKeyOrDefault("Icon48");
+			var icon72Node = yaml.NodeWithKeyOrDefault("Icon72");
 			if (labelNode == null)
 				return null;
 

OpenRA.Game/PlayerProfile.cs

@@ -10,7 +10,6 @@
 #endregion
 
 using System.Collections.Generic;
-using System.Linq;
 
 namespace OpenRA
 {
@@ -31,7 +30,7 @@ static object LoadBadges(MiniYaml yaml)
 		{
 			var badges = new List<PlayerBadge>();
 
-			var badgesNode = yaml.Nodes.FirstOrDefault(n => n.Key == "Badges");
+			var badgesNode = yaml.NodeWithKeyOrDefault("Badges");
 			if (badgesNode != null)
 			{
 				var playerDatabase = Game.ModData.Manifest.Get<PlayerDatabase>();

OpenRA.Game/Settings.cs

@@ -385,7 +385,7 @@ public void Save()
 					else
 					{
 						// Update or add the custom value
-						var fieldYaml = sectionYaml.Value.Nodes.FirstOrDefault(n => n.Key == fli.YamlName);
+						var fieldYaml = sectionYaml.Value.NodeWithKeyOrDefault(fli.YamlName);
 						if (fieldYaml != null)
 							fieldYaml.Value.Value = serialized;
 						else

OpenRA.Game/Traits/TraitsInterfaces.cs

@@ -11,7 +11,6 @@
 
 using System;
 using System.Collections.Generic;
-using System.Collections.Immutable;
 using System.Collections.ObjectModel;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
@@ -350,7 +349,7 @@ public interface INotifyGameSaved { void GameSaved(World w); }
 	public interface IGameSaveTraitData
 	{
 		List<MiniYamlNode> IssueTraitData(Actor self);
-		void ResolveTraitData(Actor self, ImmutableArray<MiniYamlNode> data);
+		void ResolveTraitData(Actor self, MiniYaml data);
 	}
 
 	[RequireExplicitImplementation]

OpenRA.Game/Widgets/WidgetLoader.cs

@@ -66,7 +66,7 @@ public Widget LoadWidget(WidgetArgs args, Widget parent, MiniYamlNode node)
 					foreach (var c in child.Value.Nodes)
 						LoadWidget(args, widget, c);
 
-			var logicNode = node.Value.Nodes.FirstOrDefault(n => n.Key == "Logic");
+			var logicNode = node.Value.NodeWithKeyOrDefault("Logic");
 			var logic = logicNode?.Value.ToDictionary();
 			args.Add("logicArgs", logic);
 

OpenRA.Game/World.cs

@@ -423,7 +423,7 @@ public void Tick()
 					if (tp.Actor == null)
 						break;
 
-					tp.Trait.ResolveTraitData(tp.Actor, kv.Value.Nodes);
+					tp.Trait.ResolveTraitData(tp.Actor, kv.Value);
 				}
 
 				gameSaveTraitData.Clear();

OpenRA.Mods.Cnc/Graphics/ClassicTilesetSpecificSpriteSequence.cs

@@ -10,7 +10,6 @@
 #endregion
 
 using System.Collections.Generic;
-using System.Linq;
 using OpenRA.Graphics;
 using OpenRA.Mods.Common.Graphics;
 
@@ -39,10 +38,10 @@ public ClassicTilesetSpecificSpriteSequence(SpriteCache cache, ISpriteSequenceLo
 
 		protected override IEnumerable<ReservationInfo> ParseFilenames(ModData modData, string tileset, int[] frames, MiniYaml data, MiniYaml defaults)
 		{
-			var node = data.Nodes.FirstOrDefault(n => n.Key == TilesetFilenames.Key) ?? defaults.Nodes.FirstOrDefault(n => n.Key == TilesetFilenames.Key);
+			var node = data.NodeWithKeyOrDefault(TilesetFilenames.Key) ?? defaults.NodeWithKeyOrDefault(TilesetFilenames.Key);
 			if (node != null)
 			{
-				var tilesetNode = node.Value.Nodes.FirstOrDefault(n => n.Key == tileset);
+				var tilesetNode = node.Value.NodeWithKeyOrDefault(tileset);
 				if (tilesetNode != null)
 				{
 					var loadFrames = CalculateFrameIndices(start, length, stride ?? length ?? 0, facings, frames, transpose, reverseFacings, shadowStart);
@@ -55,10 +54,10 @@ protected override IEnumerable<ReservationInfo> ParseFilenames(ModData modData,
 
 		protected override IEnumerable<ReservationInfo> ParseCombineFilenames(ModData modData, string tileset, int[] frames, MiniYaml data)
 		{
-			var node = data.Nodes.FirstOrDefault(n => n.Key == TilesetFilenames.Key);
+			var node = data.NodeWithKeyOrDefault(TilesetFilenames.Key);
 			if (node != null)
 			{
-				var tilesetNode = node.Value.Nodes.FirstOrDefault(n => n.Key == tileset);
+				var tilesetNode = node.Value.NodeWithKeyOrDefault(tileset);
 				if (tilesetNode != null)
 				{
 					if (frames == null)