Add test to prevent adding unserializable types to Config

src/BizHawk.Tests/Client.Common/config/SerializationStabilityTests.cs

@@ -0,0 +1,84 @@
+using System;
+using System.Collections.Generic;
+using System.Reflection;
+
+using BizHawk.Client.Common;
+
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+using Newtonsoft.Json.Linq;
+
+namespace BizHawk.Tests.Client.Common.config
+{
+	[TestClass]
+	public sealed class SerializationStabilityTests
+	{
+		private static readonly IReadOnlySet<Type> KnownGoodFromStdlib = new HashSet<Type>
+		{
+			typeof(bool),
+			typeof(DateTime),
+			typeof(Dictionary<,>),
+			typeof(int),
+			typeof(JToken),
+			typeof(Nullable<>),
+			typeof(object),
+			typeof(float),
+			typeof(string),
+		};
+
+		private static readonly IReadOnlyDictionary<Type, string> KnownGoodFromBizHawk = new Dictionary<Type, string>
+		{
+			[typeof(AnalogBind)] = "TODO",
+			[typeof(BindingCollection)] = "TODO",
+			[typeof(CheatConfig)] = "TODO",
+			[typeof(FeedbackBind)] = "TODO",
+			[typeof(MessagePosition)] = "TODO",
+			[typeof(MovieConfig)] = "TODO",
+			[typeof(PathEntryCollection)] = "TODO",
+			[typeof(RecentFiles)] = "TODO",
+			[typeof(RewindConfig)] = "TODO",
+			[typeof(SaveStateConfig)] = "TODO",
+			[typeof(ToolDialogSettings)] = "TODO",
+			[typeof(ZoomFactors)] = "TODO",
+		};
+
+		[TestMethod]
+		public void AssertAllTypesKnownSerializable()
+		{
+			static void CheckMemberAndTypeParams(Type t, string groupDesc)
+			{
+				if (t.IsEnum) return;
+				if (t.IsConstructedGenericType)
+				{
+					CheckMemberAndTypeParams(t.GetGenericTypeDefinition(), groupDesc);
+					foreach (var typeParam in t.GenericTypeArguments) CheckMemberAndTypeParams(typeParam, groupDesc);
+					return;
+				}
+				Assert.IsTrue(KnownGoodFromStdlib.Contains(t) || KnownGoodFromBizHawk.ContainsKey(t), $"type {t.FullName}, present in {groupDesc}, may not be serializable");
+			}
+			static void CheckAll<T>(string? groupDesc = null)
+			{
+				var t = typeof(T);
+				groupDesc ??= t.Name;
+				foreach (var mi in t.GetMembers(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic))
+				{
+					if (mi is PropertyInfo pi) CheckMemberAndTypeParams(pi.PropertyType, groupDesc);
+					else if (mi is FieldInfo fi) CheckMemberAndTypeParams(fi.FieldType, groupDesc);
+				}
+			}
+			CheckAll<Config>();
+		}
+
+#if false
+		[TestMethod]
+		public void TestRoundTripSerialization()
+		{
+			foreach (var kvp in KnownGoodFromBizHawk)
+			{
+				//TODO deserialize kvp.Value as an instance of the type kvp.Key, then reserialize it and compare that to kvp.Value
+				// should probably clean up the types in question first
+			}
+		}
+#endif
+	}
+}