More nullability

src/BizHawk.Client.Common/Api/Classes/EmulationApi.cs

@@ -83,7 +83,7 @@ namespace BizHawk.Client.Common
 				{
 					return new {
 						disasm = DisassemblableCore.Disassemble(
-							string.IsNullOrEmpty(name) ? MemoryDomains.SystemBus : MemoryDomains[name],
+							string.IsNullOrEmpty(name) ? MemoryDomains.SystemBus : MemoryDomains[name]!,
 							pc,
 							out var l
 						),

src/BizHawk.Client.Common/CoreFileProvider.cs

@@ -1,4 +1,6 @@
-using System.Collections.Generic;
+#nullable enable
+
+using System.Collections.Generic;
 using System.IO;
 using BizHawk.Common.PathExtensions;
 using BizHawk.Emulation.Common;
@@ -49,10 +51,10 @@ namespace BizHawk.Client.Common
 			return null;
 		}
 
-		private (byte[] FW, string Path) GetFirmwareWithPathOrThrow(FirmwareID id, string msg)
+		private (byte[] FW, string Path) GetFirmwareWithPathOrThrow(FirmwareID id, string? msg)
 			=> GetFirmwareWithPath(id) ?? throw new MissingFirmwareException($"Couldn't find required firmware {id}.  This is fatal{(msg is null ? "." : $": {msg}")}");
 
-		public byte[] GetFirmware(FirmwareID id, string msg = null)
+		public byte[]? GetFirmware(FirmwareID id, string? msg = null)
 		{
 			var tuple = GetFirmwareWithPath(id);
 			if (tuple is null && msg is not null)
@@ -62,10 +64,10 @@ namespace BizHawk.Client.Common
 			return tuple?.FW;
 		}
 
-		public byte[] GetFirmwareOrThrow(FirmwareID id, string msg = null)
+		public byte[] GetFirmwareOrThrow(FirmwareID id, string? msg = null)
 			=> GetFirmwareWithPathOrThrow(id, msg).FW;
 
-		public (byte[] FW, GameInfo Game) GetFirmwareWithGameInfoOrThrow(FirmwareID id, string msg = null)
+		public (byte[] FW, GameInfo Game) GetFirmwareWithGameInfoOrThrow(FirmwareID id, string? msg = null)
 		{
 			var (fw, path) = GetFirmwareWithPathOrThrow(id, msg);
 			return (fw, Database.GetGameInfo(fw, path));

src/BizHawk.Emulation.Common/Base Implementations/BasicServiceProvider.cs

@@ -1,6 +1,4 @@
-#nullable disable
+using System;
-
-using System;
 using System.Collections.Generic;
 using System.Linq;
 
@@ -41,7 +39,7 @@ namespace BizHawk.Emulation.Common
 			while (coreType != typeof(object))
 			{
 				_services.Add(coreType, core);
-				coreType = coreType.BaseType;
+				coreType = coreType.BaseType!;
 			}
 		}
 
@@ -49,23 +47,16 @@ namespace BizHawk.Emulation.Common
 		/// <typeparam name="T">The <see cref="IEmulatorService"/> to register</typeparam>
 		/// <exception cref="ArgumentNullException"><paramref name="provider"/> is null</exception>
 		public void Register<T>(T provider)
-			where T : IEmulatorService
+			where T : class, IEmulatorService
 		{
-			if (provider == null)
-			{
-				throw new ArgumentNullException(nameof(provider));
-			}
-
 			_services[typeof(T)] = provider;
 		}
 
 		public T GetService<T>()
 			where T : IEmulatorService
-		{
+			=> (T) GetService(typeof(T))!;
-			return (T)GetService(typeof(T));
-		}
 
-		public object GetService(Type t)
+		public object? GetService(Type t)
 		{
 			return _services.TryGetValue(t, out var service) ? service : null;
 		}

src/BizHawk.Emulation.Common/Base Implementations/CallbackBasedTraceBuffer.cs

@@ -1,6 +1,4 @@
-#nullable disable
+using System;
-
-using System;
 using System.Collections.Generic;
 using System.Linq;
 
@@ -48,9 +46,9 @@ namespace BizHawk.Emulation.Common
 
 		protected abstract void TraceFromCallback(uint addr, uint value, uint flags);
 
-		private ITraceSink _sink;
+		private ITraceSink? _sink;
 
-		public ITraceSink Sink
+		public ITraceSink? Sink
 		{
 			get => _sink;
 			set
@@ -68,6 +66,7 @@ namespace BizHawk.Emulation.Common
 
 		public string Header { get; }
 
+#nullable disable
 		private class TracingMemoryCallback : IMemoryCallback
 		{
 			public TracingMemoryCallback(MemoryCallbackDelegate callback, string scope)
@@ -88,5 +87,6 @@ namespace BizHawk.Emulation.Common
 
 			public string Scope { get; }
 		}
+#nullable restore
 	}
 }

src/BizHawk.Emulation.Common/Base Implementations/InputCallbackSystem.cs

@@ -1,6 +1,4 @@
-#nullable disable
+using System;
-
-using System;
 using System.Collections.Generic;
 using System.Linq;
 
@@ -57,7 +55,7 @@ namespace BizHawk.Emulation.Common
 		}
 
 		public delegate void ActiveChangedEventHandler();
-		public event ActiveChangedEventHandler ActiveChanged;
+		public event ActiveChangedEventHandler? ActiveChanged;
 
 		private void Changes(bool hadAny, bool hasAny)
 		{

src/BizHawk.Emulation.Common/Base Implementations/MemoryBasedInputCallbackSystem.cs

@@ -1,6 +1,4 @@
-#nullable disable
+using System;
-
-using System;
 using System.Collections;
 using System.Collections.Generic;
 
@@ -18,11 +16,6 @@ namespace BizHawk.Emulation.Common
 
 		public MemoryBasedInputCallbackSystem(IDebuggable debuggableCore, string scope, IEnumerable<uint> addresses)
 		{
-			if (addresses == null)
-			{
-				throw new ArgumentException($"{nameof(addresses)} cannot be null.");
-			}
-
 			if (!debuggableCore.MemoryCallbacksAvailable())
 			{
 				throw new InvalidOperationException("Memory callbacks are required");

src/BizHawk.Emulation.Common/Base Implementations/NullSound.cs

@@ -1,6 +1,4 @@
-#nullable disable
+using System;
-
-using System;
 
 namespace BizHawk.Emulation.Common
 {

src/BizHawk.Emulation.Common/Base Implementations/NullVideo.cs

@@ -1,6 +1,4 @@
-#nullable disable
+namespace BizHawk.Emulation.Common
-
-namespace BizHawk.Emulation.Common
 {
 	/// <summary>
 	/// A default IVideoProvider that simply returns

src/BizHawk.Emulation.Common/Base Implementations/SimpleSyncSoundProvider.cs

@@ -1,6 +1,4 @@
-#nullable disable
+using System;
-
-using System;
 
 namespace BizHawk.Emulation.Common.Base_Implementations
 {

src/BizHawk.Emulation.Common/CoreComms.cs

@@ -1,6 +1,4 @@
-#nullable disable
+using System;
-
-using System;
 
 namespace BizHawk.Emulation.Common
 {

src/BizHawk.Emulation.Common/Interfaces/ICoreFileProvider.cs

@@ -1,6 +1,4 @@
-#nullable disable
+namespace BizHawk.Emulation.Common
-
-namespace BizHawk.Emulation.Common
 {
 	/// <summary>
 	/// Defines the means by which firmware, bios and other necessary files are provided to a core that needs them
@@ -24,15 +22,15 @@ namespace BizHawk.Emulation.Common
 
 		/// <param name="msg">warning message to show on failure</param>
 		/// <returns><see langword="null"/> iff failed</returns>
-		byte[] GetFirmware(FirmwareID id, string msg = null);
+		byte[]? GetFirmware(FirmwareID id, string? msg = null);
 
 		/// <param name="msg">exception message to show on failure</param>
 		/// <exception cref="MissingFirmwareException">if not found</exception>
-		byte[] GetFirmwareOrThrow(FirmwareID id, string msg = null);
+		byte[] GetFirmwareOrThrow(FirmwareID id, string? msg = null);
 
 		/// <param name="msg">exception message to show on failure</param>
 		/// <exception cref="MissingFirmwareException">if not found</exception>
 		/// <remarks>only used in PCEHawk</remarks>
-		(byte[] FW, GameInfo Game) GetFirmwareWithGameInfoOrThrow(FirmwareID id, string msg = null);
+		(byte[] FW, GameInfo Game) GetFirmwareWithGameInfoOrThrow(FirmwareID id, string? msg = null);
 	}
 }

src/BizHawk.Emulation.Common/Interfaces/IEmulatorServiceProvider.cs

@@ -1,6 +1,4 @@
-#nullable disable
+using System;
-
-using System;
 using System.Collections.Generic;
 
 namespace BizHawk.Emulation.Common
@@ -29,7 +27,7 @@ namespace BizHawk.Emulation.Common
 
 		/// <summary>
 		/// Returns an instance of T if T is available
-		/// Else returns null
+		/// Else throws NRE
 		/// </summary>
 		/// <typeparam name="T">The requested <see cref="IEmulatorService"/></typeparam>
 		T GetService<T>() where T : IEmulatorService;
@@ -38,7 +36,7 @@ namespace BizHawk.Emulation.Common
 		/// Returns an instance of t if t is available
 		/// Else returns null
 		/// </summary>
-		object GetService(Type t);
+		object? GetService(Type t);
 
 		/// <summary>
 		/// Gets a list of all currently registered services available to be retrieved

src/BizHawk.Emulation.Common/Interfaces/IInputCallbackSystem.cs

@@ -1,6 +1,4 @@
-#nullable disable
+using System;
-
-using System;
 using System.Collections.Generic;
 
 namespace BizHawk.Emulation.Common

src/BizHawk.Emulation.Common/Interfaces/Services/IDisassemblable.cs

@@ -1,6 +1,4 @@
-#nullable disable
+using System;
-
-using System;
 using System.Linq;
 using System.Collections.Generic;
 
@@ -40,12 +38,12 @@ namespace BizHawk.Emulation.Common
 	/// </summary>
 	public abstract class VerifiedDisassembler : IDisassemblable
 	{
-		private string _cpu;
+		private string? _cpu;
 
 		/// <exception cref="ArgumentException">(from setter) <paramref name="value"/> isn't the name of an available CPU</exception>
 		public virtual string Cpu
 		{
-			get => _cpu;
+			get => _cpu ??= AvailableCpus.First();
 			set
 			{
 				if (!AvailableCpus.Contains(value))
@@ -62,10 +60,5 @@ namespace BizHawk.Emulation.Common
 		public abstract string PCRegisterName { get; }
 
 		public abstract string Disassemble(MemoryDomain m, uint addr, out int length);
-
-		protected VerifiedDisassembler()
-		{
-			_cpu = AvailableCpus.First();
-		}
 	}
 }

src/BizHawk.Emulation.Common/ServiceAttributes.cs

@@ -1,6 +1,4 @@
-#nullable disable
+using System;
-
-using System;
 using System.Collections.Generic;
 using System.Linq;
 
@@ -26,7 +24,7 @@ namespace BizHawk.Emulation.Common
 	public sealed class ServiceNotApplicableAttribute : Attribute
 	{
 		/// <remarks>TODO neither array nor <see cref="IEnumerable{T}"/> is the correct collection to be using here, try <see cref="IReadOnlyList{T}"/>/<see cref="IReadOnlyCollection{T}"/> instead</remarks>
-		public ServiceNotApplicableAttribute(Type[] types)
+		public ServiceNotApplicableAttribute(Type[]? types)
 		{
 			NotApplicableTypes = types?.AsEnumerable() ?? Enumerable.Empty<Type>();
 		}

src/BizHawk.Emulation.Common/ServiceInjector.cs

@@ -1,6 +1,4 @@
-#nullable disable
+using System;
-
-using System;
 using System.Linq;
 
 using BizHawk.Common.ReflectionExtensions;
@@ -18,7 +16,7 @@ namespace BizHawk.Emulation.Common
 		public static void ClearServices(object target)
 		{
 			Type targetType = target.GetType();
-			object[] tmp = new object[1];
+			object?[] tmp = { null };
 
 			foreach (var propInfo in
 				targetType.GetPropertiesWithAttrib(typeof(RequiredServiceAttribute))
@@ -35,7 +33,7 @@ namespace BizHawk.Emulation.Common
 		public static bool UpdateServices(IEmulatorServiceProvider source, object target)
 		{
 			Type targetType = target.GetType();
-			object[] tmp = new object[1];
+			object?[] tmp = new object?[1];
 
 			foreach (var propInfo in targetType.GetPropertiesWithAttrib(typeof(RequiredServiceAttribute)))
 			{

src/BizHawk.Emulation.Common/SystemLookup.cs

@@ -1,6 +1,4 @@
-#nullable disable
+using System.Collections.Generic;
-
-using System.Collections.Generic;
 using System.Linq;
 
 namespace BizHawk.Emulation.Common

src/BizHawk.Emulation.Common/vpads_schemata/IVirtualPadSchema.cs

@@ -1,8 +1,5 @@
-#nullable disable
+using System;
-
-using System;
 using System.Collections.Generic;
-using BizHawk.Emulation.Common;
 
 namespace BizHawk.Emulation.Common
 {

src/BizHawk.Emulation.Common/vpads_schemata/PadSchema.cs

@@ -1,6 +1,4 @@
-#nullable disable
+using System.Collections.Generic;
-
-using System.Collections.Generic;
 using System.Drawing;
 
 namespace BizHawk.Emulation.Common
@@ -8,9 +6,13 @@ namespace BizHawk.Emulation.Common
 	public class PadSchema
 	{
 		public Size Size { get; set; }
+
 		public bool IsConsole { get; protected set; }
+
 		public IEnumerable<PadSchemaControl> Buttons { get; set; } = new List<PadSchemaControl>();
-		public string DisplayName { get; set; } // The name of the pad itself, presumably will be displayed by the given pad time if supplied
+
+		/// <summary>The name of the pad itself, presumably will be displayed by the given pad time if supplied</summary>
+		public string? DisplayName { get; set; }
 	}
 
 	public class ConsoleSchema : PadSchema