[2020-02][debugger] Fix NOT_IMPLEMENTED while debugging. (#19450)

* Backporting this, and after this I will backport the bump protocol for this PR.

* Bump API snapshot submodule

Co-authored-by: monojenkins <jo.shields+jenkins@xamarin.com>

4 files changed, 35 insertions, 4 deletions

diff --git a/mcs/class/Mono.Debugger.Soft/Mono.Debugger.Soft/Connection.cs b/mcs/class/Mono.Debugger.Soft/Mono.Debugger.Soft/Connection.cs
index 03724b7f7bc..70de4ad7bea 100644
--- a/mcs/class/Mono.Debugger.Soft/Mono.Debugger.Soft/Connection.cs
+++ b/mcs/class/Mono.Debugger.Soft/Mono.Debugger.Soft/Connection.cs
@@ -409,6 +409,9 @@ namespace Mono.Debugger.Soft
 		public ErrorCode ErrorCode {
 			get; set;
 		}
+		public string ErrorMessage {
+			get; set;
+		}
 	}
 
 	/*
@@ -792,10 +795,12 @@ namespace Mono.Debugger.Soft
 
 				// For reply packets
 				offset = 0;
-				ReadInt (); // length
+				var len = ReadInt (); // length
 				ReadInt (); // id
 				ReadByte (); // flags
 				ErrorCode = ReadShort ();
+				if (ErrorCode == (int)Mono.Debugger.Soft.ErrorCode.INVALID_ARGUMENT && len > offset)
+					ErrorMsg = ReadString ();
 			}
 
 			public CommandSet CommandSet {
@@ -810,6 +815,10 @@ namespace Mono.Debugger.Soft
 				get; set;
 			}
 
+			public string ErrorMsg {
+				get; internal set;
+			}
+
 			public int Offset {
 				get {
 					return offset;
@@ -1792,7 +1801,7 @@ namespace Mono.Debugger.Soft
 							LogPacket (packetId, encoded_packet, reply, command_set, command, watch);
 						if (r.ErrorCode != 0) {
 							if (ErrorHandler != null)
-								ErrorHandler (this, new ErrorHandlerEventArgs () { ErrorCode = (ErrorCode)r.ErrorCode });
+								ErrorHandler (this, new ErrorHandlerEventArgs () { ErrorCode = (ErrorCode)r.ErrorCode, ErrorMessage = r.ErrorMsg});
 							throw new NotImplementedException ("No error handler set.");
 						} else {
 							return r;
diff --git a/mcs/class/Mono.Debugger.Soft/Mono.Debugger.Soft/VirtualMachine.cs b/mcs/class/Mono.Debugger.Soft/Mono.Debugger.Soft/VirtualMachine.cs
index 12274864d4c..f85e807201f 100644
--- a/mcs/class/Mono.Debugger.Soft/Mono.Debugger.Soft/VirtualMachine.cs
+++ b/mcs/class/Mono.Debugger.Soft/Mono.Debugger.Soft/VirtualMachine.cs
@@ -371,7 +371,7 @@ namespace Mono.Debugger.Soft
 			case ErrorCode.NO_SEQ_POINT_AT_IL_OFFSET:
 				throw new ArgumentException ("Cannot set breakpoint on the specified IL offset.");
 			default:
-				throw new CommandException (args.ErrorCode);
+				throw new CommandException (args.ErrorCode, args.ErrorMessage);
 			}
 		}
 
@@ -887,13 +887,18 @@ namespace Mono.Debugger.Soft
 
 	public class CommandException : Exception {
 
-		internal CommandException (ErrorCode error_code) : base ("Debuggee returned error code " + error_code + ".") {
+		internal CommandException (ErrorCode error_code, string error_message) : base ("Debuggee returned error code " + error_code + (error_message == null || error_message.Length == 0 ? "." : " - " + error_message + ".")) {
 			ErrorCode = error_code;
+			ErrorMessage = error_message;
 		}
 
 		public ErrorCode ErrorCode {
 			get; set;
 		}
+
+		public string ErrorMessage {
+			get; internal set;
+		}
 	}
 
 	public class VMNotSuspendedException : InvalidOperationException
diff --git a/mcs/class/Mono.Debugger.Soft/Test/dtest-app.cs b/mcs/class/Mono.Debugger.Soft/Test/dtest-app.cs
index e6b79fdd406..2f77ac510c6 100644
--- a/mcs/class/Mono.Debugger.Soft/Test/dtest-app.cs
+++ b/mcs/class/Mono.Debugger.Soft/Test/dtest-app.cs
@@ -617,6 +617,7 @@ public class Tests : TestsBase, ITest2
 			ss_multi_thread ();
 			return 0;
 		}
+		test_invalid_argument_assembly_get_type ();
 		return 3;
 	}
 
@@ -645,6 +646,10 @@ public class Tests : TestsBase, ITest2
 		LocalReflectClass.RunMe ();
 	}
 
+	public static void test_invalid_argument_assembly_get_type () {
+
+	}
+
 	public static void breakpoints () {
 		/* Call these early so it is JITted by the time a breakpoint is placed on it */
 		bp3 ();
diff --git a/mcs/class/Mono.Debugger.Soft/Test/dtest.cs b/mcs/class/Mono.Debugger.Soft/Test/dtest.cs
index d6ca7dc3255..a8f12094bbd 100644
--- a/mcs/class/Mono.Debugger.Soft/Test/dtest.cs
+++ b/mcs/class/Mono.Debugger.Soft/Test/dtest.cs
@@ -5202,6 +5202,18 @@ public class DebuggerTests
 	}
 	
 	[Test]
+	public void InvalidArgumentAssemblyGetType () {
+		Event e = run_until ("test_invalid_argument_assembly_get_type");
+		var assembly = entry_point.DeclaringType.Assembly;
+		try {
+			var type = assembly.GetType ("System.Collections.Generic.Dictionary<double, float>.Main");
+		}
+		catch (CommandException ex) {
+			Assert.AreEqual(ex.ErrorMessage, "Unexpected assembly-qualified type \"System.Collections.Generic.Dictionary<double, float>.Main\" was provided");
+		}
+	}
+	
+	[Test]
 	public void CheckSuspendPolicySentWhenLaunchSuspendYes () {
 		vm.Exit (0);
 		var port = GetFreePort ();