Create a MissingFirmwareException in Emulation.Common, and catch this in the Rom loading logic, on the client side, respond to this type of error with a nice message and an option to configure their firmware. Have NesHawk throw this exception when there is a missing FDS Bios. Other cores will need to be implemented this way too at some point

BizHawk.Client.Common/RomLoader.cs

@@ -29,6 +29,8 @@ namespace BizHawk.Client.Common
 {
 	public class RomLoader
 	{
+		public enum LoadErrorType { Unknown, MissingFirmware, XML }
+
 		// helper methods for the settings events
 		private object GetCoreSettings<T>()
 			where T : IEmulator
@@ -70,14 +72,16 @@ namespace BizHawk.Client.Common
 		public class RomErrorArgs : EventArgs
 		{
 			// TODO: think about naming here, what to pass, a lot of potential good information about what went wrong could go here!
-			public RomErrorArgs(string message, string systemId)
+			public RomErrorArgs(string message, string systemId, LoadErrorType type)
 			{
 				Message = message;
 				AttemptedCoreLoad = systemId;
+				Type = type;
 			}
 
 			public string Message { get; private set; }
 			public string AttemptedCoreLoad { get; private set; }
+			public LoadErrorType Type { get; private set; }
 		}
 
 		public class SettingsLoadArgs : EventArgs
@@ -112,11 +116,11 @@ namespace BizHawk.Client.Common
 			return null;
 		}
 
-		private void ThrowLoadError(string message, string systemId)
+		private void DoLoadErrorCallback(string message, string systemId, LoadErrorType type = LoadErrorType.Unknown)
 		{
 			if (OnLoadError != null)
 			{
-				OnLoadError(this, new RomErrorArgs(message, systemId));
+				OnLoadError(this, new RomErrorArgs(message, systemId, type));
 			}
 		}
 
@@ -270,7 +274,7 @@ namespace BizHawk.Client.Common
 						}
 						catch (Exception ex)
 						{
-							ThrowLoadError(ex.ToString(), "XMLGame Load Error"); // TODO: don't pass in XMLGame Load Error as a system ID
+							DoLoadErrorCallback(ex.ToString(), "DGB", LoadErrorType.XML);
 							return false;
 						}
 					}
@@ -387,7 +391,7 @@ namespace BizHawk.Client.Common
 									catch
 									{
 										// failed to load SGB bios.  to avoid catch-22, disable SGB mode
-										ThrowLoadError("Failed to load a GB rom in SGB mode.  Disabling SGB Mode.", game.System);
+										DoLoadErrorCallback("Failed to load a GB rom in SGB mode.  Disabling SGB Mode.", game.System);
 										Global.Config.GB_AsSGB = false;
 										throw;
 									}
@@ -433,7 +437,7 @@ namespace BizHawk.Client.Common
 
 					if (nextEmulator == null)
 					{
-						ThrowLoadError("No core could load the rom.", null);
+						DoLoadErrorCallback("No core could load the rom.", null);
 						return false;
 					}
 				}
@@ -450,9 +454,13 @@ namespace BizHawk.Client.Common
 					{
 						return LoadRom(path, nextComm, forceAccurateCore: true);
 					}
+					else if (ex is MissingFirmwareException)
+					{
+						DoLoadErrorCallback(ex.Message, system, LoadErrorType.MissingFirmware);
+					}
 					else
 					{
-						ThrowLoadError("A core accepted the rom, but threw an exception while loading it:\n\n" + ex, system);
+						DoLoadErrorCallback("A core accepted the rom, but threw an exception while loading it:\n\n" + ex, system);
 					}
 
 					return false;

BizHawk.Client.EmuHawk/MainForm.cs

@@ -3021,11 +3021,28 @@ namespace BizHawk.Client.EmuHawk
 
 		private void ShowLoadError(object sender, RomLoader.RomErrorArgs e)
 		{
-			string title = "load error";
-			if (e.AttemptedCoreLoad != null)
-				title = e.AttemptedCoreLoad + " load error";
+			if (e.Type == RomLoader.LoadErrorType.MissingFirmware)
+			{
+				var result = MessageBox.Show(
+					"You are missing the needed firmware files to load this Rom\n\nWould you like to open the firmware manager now and configure your firmwares?",
+					e.Message,
+					MessageBoxButtons.YesNo,
+					MessageBoxIcon.Error);
+				if (result == DialogResult.Yes)
+				{
+					FirmwaresMenuItem_Click(null, null);
+				}
+			}
+			else
+			{
+				string title = "load error";
+				if (e.AttemptedCoreLoad != null)
+				{
+					title = e.AttemptedCoreLoad + " load error";
+				}
 
-			MessageBox.Show(this, e.Message, title, MessageBoxButtons.OK, MessageBoxIcon.Error);
+				MessageBox.Show(this, e.Message, title, MessageBoxButtons.OK, MessageBoxIcon.Error);
+			}
 		}
 
 		private void NotifyCoreComm(string message)

BizHawk.Client.EmuHawk/tools/BatchRunner.cs

@@ -76,7 +76,7 @@ namespace BizHawk.Client.EmuHawk
 		void OnLoadError(object sender, RomLoader.RomErrorArgs e)
 		{
 			current.Status = Result.EStatus.ErrorOnLoad;
-			current.Messages.Add(string.Format("OnLoadError: {0}, {1}", e.AttemptedCoreLoad, e.Message));
+			current.Messages.Add(string.Format("OnLoadError: {0}, {1}, {2}", e.AttemptedCoreLoad, e.Message, e.Type.ToString()));
 		}
 
 		void CommMessage(string msg)

BizHawk.Emulation.Common/BizHawk.Emulation.Common.csproj

@@ -54,6 +54,7 @@
     <Compile Include="Database\Database.cs" />
     <Compile Include="Database\FirmwareDatabase.cs" />
     <Compile Include="Database\GameInfo.cs" />
+    <Compile Include="EmulationExceptions.cs" />
     <Compile Include="Extensions.cs" />
     <Compile Include="Interfaces\Base Implementations\NullController.cs" />
     <Compile Include="Interfaces\Base Implementations\NullEmulator.cs" />

BizHawk.Emulation.Common/EmulationExceptions.cs

@@ -0,0 +1,12 @@
+using System;
+
+namespace BizHawk.Emulation.Common
+{
+	public class MissingFirmwareException : Exception
+	{
+		public MissingFirmwareException(string message) : base(message)
+		{
+
+		}
+	}
+}

BizHawk.Emulation.Cores/Consoles/Nintendo/NES/NES.cs

@@ -511,7 +511,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 				origin = EDetectionOrigin.FDS;
 				LoadWriteLine("Found FDS header.");
 				if (fdsbios == null)
-					throw new Exception("Missing FDS Bios!");
+					throw new MissingFirmwareException("Missing FDS Bios");
 				cart = new CartInfo();
 				var fdsboard = new FDS();
 				fdsboard.biosrom = fdsbios;