Refactor `ServiceInjector`

src/BizHawk.Client.EmuHawk/Api/ApiManager.cs

@@ -2,6 +2,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Linq;
 using System.Reflection;
 
@@ -62,7 +63,7 @@ namespace BizHawk.Client.EmuHawk
 					tuple =>
 					{
 						var instance = tuple.Ctor.Invoke(tuple.CtorTypes.Select(t => avail[t]).ToArray());
-						ServiceInjector.UpdateServices(serviceProvider, instance);
+						Debug.Assert(ServiceInjector.UpdateServices(serviceProvider, instance, mayCache: true));
 						return (IExternalApi) instance;
 					}));
 		}

src/BizHawk.Client.EmuHawk/tools/Lua/LuaLibraries.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.ComponentModel;
+using System.Diagnostics;
 using System.IO;
 using System.Linq;
 using System.Reflection;
@@ -65,7 +66,7 @@ namespace BizHawk.Client.EmuHawk
 					|| lib.GetCustomAttribute<LuaLibraryAttribute>(inherit: false)?.Released is not false)
 				{
 					var instance = (LuaLibraryBase)Activator.CreateInstance(lib, this, _apiContainer, (Action<string>)LogToLuaConsole);
-					ServiceInjector.UpdateServices(serviceProvider, instance);
+					Debug.Assert(ServiceInjector.UpdateServices(serviceProvider, instance, mayCache: true));
 
 					// TODO: make EmuHawk libraries have a base class with common properties such as this
 					// and inject them here
@@ -181,7 +182,7 @@ namespace BizHawk.Client.EmuHawk
 			foreach (var lib in Libraries.Values)
 			{
 				lib.APIs = _apiContainer;
-				ServiceInjector.UpdateServices(newServiceProvider, lib);
+				Debug.Assert(ServiceInjector.UpdateServices(newServiceProvider, lib, mayCache: true));
 				lib.Restarted();
 			}
 		}

src/BizHawk.Client.EmuHawk/tools/ToolManager.cs

@@ -123,7 +123,7 @@ namespace BizHawk.Client.EmuHawk
 			if (!(CreateInstance<T>(toolPath) is T newTool)) return null;
 
 			if (newTool is Form form) form.Owner = _owner;
-			if (!ServiceInjector.UpdateServices(_emulator.ServiceProvider, newTool)) return null;
+			if (!ServiceInjector.UpdateServices(_emulator.ServiceProvider, newTool)) return null; //TODO pass `true` for `mayCache` when from EmuHawk assembly
 			SetBaseProperties(newTool);
 			var toolTypeName = typeof(T).FullName!;
 			// auto settings

src/BizHawk.Emulation.Common/ServiceInjector.cs

@@ -1,5 +1,7 @@
 using System;
+using System.Collections.Generic;
 using System.Linq;
+using System.Reflection;
 
 using BizHawk.Common.ReflectionExtensions;
 
@@ -10,30 +12,71 @@ namespace BizHawk.Emulation.Common
 	/// </summary>
 	public static class ServiceInjector
 	{
+		private readonly struct ServicePropInfo
+		{
+			public readonly Type PropType;
+
+			public readonly MethodInfo Setter;
+
+			public ServicePropInfo(Type propType, MethodInfo setter)
+			{
+				PropType = propType;
+				Setter = setter;
+			}
+		}
+
+		private static readonly Dictionary<Type, (List<ServicePropInfo> Req, List<ServicePropInfo> Opt)> _cache = new();
+
+		private static (List<ServicePropInfo> Req, List<ServicePropInfo> Opt) GetServicePropsFor(
+			this Type @class,
+			bool mayCache)
+		{
+			if (_cache.TryGetValue(@class, out var pair)) return pair;
+			pair = (new(), new());
+			foreach (var pi in @class.GetProperties(ReflectionExtensions.DI_TARGET_PROPS))
+			{
+				//TODO enumerate attrs only once
+				if (pi.GetCustomAttributes(typeof(RequiredServiceAttribute), inherit: false).Length is not 0)
+				{
+					pair.Req.Add(new(pi.PropertyType, pi.GetSetMethod(nonPublic: true)));
+				}
+				else if (pi.GetCustomAttributes(typeof(OptionalServiceAttribute), inherit: false).Length is not 0)
+				{
+					pair.Opt.Add(new(pi.PropertyType, pi.GetSetMethod(nonPublic: true)));
+				}
+			}
+			if (mayCache) _cache[@class] = pair;
+			return pair;
+		}
+
 		/// <summary>
 		/// Feeds the target its required services.
 		/// </summary>
+		/// <param name="mayCache">
+		/// <see langword="true"/> if the properties of <paramref name="target"/> may be written to cache,
+		/// i.e. if it's known to come from a first-party assembly and not an ext. tool.<br/>
+		/// Cache will still be read from regardless.
+		/// </param>
 		/// <returns>false if update failed</returns>
-		public static bool UpdateServices(IEmulatorServiceProvider source, object target)
+		/// <remarks>don't think having a genericised overload would be helpful, but TODO pass in type to save <c>target.GetType()</c> call</remarks>
+		public static bool UpdateServices(IEmulatorServiceProvider source, object target, bool mayCache = false)
 		{
 			Type targetType = target.GetType();
 			object?[] tmp = new object?[1];
-
-			foreach (var propInfo in targetType.GetPropertiesWithAttrib(typeof(RequiredServiceAttribute)))
+			var (req, opt) = GetServicePropsFor(targetType, mayCache: mayCache);
+			foreach (var info in req)
 			{
-				tmp[0] = source.GetService(propInfo.PropertyType);
+				tmp[0] = source.GetService(info.PropType);
 				if (tmp[0] == null)
 				{
 					return false;
 				}
-
-				propInfo.GetSetMethod(true).Invoke(target, tmp);
+				info.Setter.Invoke(target, tmp);
 			}
-
-			foreach (var propInfo in targetType.GetPropertiesWithAttrib(typeof(OptionalServiceAttribute)))
+			foreach (var info in opt)
 			{
-				tmp[0] = source.GetService(propInfo.PropertyType);
-				propInfo.GetSetMethod(true).Invoke(target, tmp);
+				tmp[0] = source.GetService(info.PropType);
+				info.Setter.Invoke(target, tmp);
 			}
 
 			return true;
@@ -44,11 +87,7 @@ namespace BizHawk.Emulation.Common
 		/// and the services provided by the emulator core.
 		/// </summary>
 		public static bool IsAvailable(IEmulatorServiceProvider source, Type targetType)
-		{
-			return targetType.GetPropertiesWithAttrib(typeof(RequiredServiceAttribute))
-				.Select(pi => pi.PropertyType)
-				.All(source.HasService);
-		}
+			=> GetServicePropsFor(targetType, mayCache: false).Req.TrueForAll(info => source.HasService(info.PropType));
 	}
 
 	[AttributeUsage(AttributeTargets.Property)]