IObjectValueSource.SetValue now throws ValueModificationException if modification is failed instead of supressing the exception. This allows to show the error info to user at the call site (e.g. in message box).

ValueReference.SetValue() and ArrayElementGroup.SetValue() implementations unified and moved to ValueModificationUtil.

Author: nerzhulart

Mono.Debugging/Mono.Debugging.Backend/IObjectValueSource.cs

@@ -28,12 +28,19 @@
 
 using System;
 using Mono.Debugging.Client;
+using Mono.Debugging.Evaluation;
 
 namespace Mono.Debugging.Backend
 {
 	public interface IObjectValueSource: IDebuggerBackendObject
 	{
 		ObjectValue[] GetChildren (ObjectPath path, int index, int count, EvaluationOptions options);
+
+		/// <summary>
+		/// Updates the value with the result of evaluation of <paramref name="value"/> expression
+		/// </summary>
+		/// <exception cref="ValueModificationException" /> call site should catch this exception and show it to user in pretty way (e.g. in message box)
+		/// All other exceptions indicate error and should be logged
 		EvaluationResult SetValue (ObjectPath path, string value, EvaluationOptions options);
 		ObjectValue GetValue (ObjectPath path, EvaluationOptions options);
 

Mono.Debugging/Mono.Debugging.Evaluation/ArrayElementGroup.cs

@@ -277,37 +277,18 @@ public static string GetArrayDescription (int[] bounds)
 
 			return sb.ToString ();
 		}
-		
-		public EvaluationResult SetValue (ObjectPath path, string value, EvaluationOptions options)
+
+		EvaluationResult IObjectValueSource.SetValue (ObjectPath path, string value, EvaluationOptions options)
 		{
 			if (path.Length != 2)
-				throw new NotSupportedException ();
+				throw new InvalidOperationException (string.Format ("ObjectPath for array element is invalid: {0}", path));
 
 			int[] idx = StringToIndices (path [1]);
-			
-			object val;
-			try {
-				EvaluationContext cctx = ctx.Clone ();
-				EvaluationOptions ops = options ?? cctx.Options;
-				ops.AllowMethodEvaluation = true;
-				ops.AllowTargetInvoke = true;
-				cctx.Options = ops;
-				ValueReference var = ctx.Evaluator.Evaluate (ctx, value, array.ElementType);
-				val = var.Value;
-				val = ctx.Adapter.Convert (ctx, val, array.ElementType);
-				array.SetElement (idx, val);
-			} catch {
-				val = array.GetElement (idx);
-			}
-			try {
-				return ctx.Evaluator.TargetObjectToExpression (ctx, val);
-			} catch (Exception ex) {
-				ctx.WriteDebuggerError (ex);
-				return new EvaluationResult ("? (" + ex.Message + ")");
-			}
+			var cctx = ctx.WithOptions (options);
+			return ValueModificationUtil.ModifyValue (cctx, value, array.ElementType, newVal => array.SetElement (idx, newVal));
 		}
-		
-		public ObjectValue GetValue (ObjectPath path, EvaluationOptions options)
+
+		ObjectValue IObjectValueSource.GetValue (ObjectPath path, EvaluationOptions options)
 		{
 			if (path.Length != 2)
 				throw new NotSupportedException ();

Mono.Debugging/Mono.Debugging.Evaluation/ValueModificationException.cs

@@ -0,0 +1,19 @@
+using System;
+
+namespace Mono.Debugging.Evaluation
+{
+	public class ValueModificationException : Exception
+	{
+		public ValueModificationException ()
+		{
+		}
+
+		public ValueModificationException (string message) : base (message)
+		{
+		}
+
+		public ValueModificationException (string message, Exception innerException) : base (message, innerException)
+		{
+		}
+	}
+}

Mono.Debugging/Mono.Debugging.Evaluation/ValueModificationUtil.cs

@@ -0,0 +1,50 @@
+using System;
+using Mono.Debugging.Backend;
+
+namespace Mono.Debugging.Evaluation
+{
+	public static class ValueModificationUtil
+	{
+		internal static ValueReference EvaluateRightHandValue (EvaluationContext context, string value, object expectedType)
+		{
+			context.Options.AllowMethodEvaluation = true;
+			context.Options.AllowTargetInvoke = true;
+			try {
+				return context.Evaluator.Evaluate (context, value, expectedType);
+			} catch (Exception e) {
+				throw new ValueModificationException(string.Format ("Cannot evaluate '{0}': {1}", value, e.Message), e);
+			}
+		}
+
+		internal static object ConvertRightHandValue (EvaluationContext context, object value, object expectedType)
+		{
+			try {
+				return context.Adapter.Convert (context, value, expectedType);
+			} catch (Exception e) {
+				throw new ValueModificationException(string.Format ("Conversion error: {0}", e.Message), e);
+			}
+		}
+
+		internal static EvaluationResult ModifyValue (EvaluationContext context, string value, object expectedType, Action<object> valueSetter)
+		{
+			var rightHandValue = EvaluateRightHandValue (context, value, expectedType);
+
+			object val;
+			try {
+				val = rightHandValue.Value;
+			} catch (Exception e) {
+				throw new ValueModificationException(string.Format ("Cannot get real object of {0}", value), e);
+			}
+			var convertedValue = ConvertRightHandValue (context, val, expectedType);
+			try {
+				valueSetter (convertedValue);
+			} catch (Exception e) {
+				throw new ValueModificationException(string.Format ("Error while assigning new value to object: {0}", e.Message), e);
+			}
+			// don't wrap with try-catch it, this call normally should not throw exceptions produced by wrong user input.
+			// If exception was occured this means something has gone wrong in we have to report it in log
+			return context.Evaluator.TargetObjectToExpression (context, convertedValue);
+		}
+
+	}
+}

Mono.Debugging/Mono.Debugging.Evaluation/ValueReference.cs

@@ -148,29 +148,9 @@ ObjectValue IObjectValueSource.GetValue (ObjectPath path, EvaluationOptions opti
 
 		EvaluationResult IObjectValueSource.SetValue (ObjectPath path, string value, EvaluationOptions options)
 		{
-			try {
-				Context.WaitRuntimeInvokes ();
-
-				var ctx = GetContext (options);
-				ctx.Options.AllowMethodEvaluation = true;
-				ctx.Options.AllowTargetInvoke = true;
-
-				var vref = ctx.Evaluator.Evaluate (ctx, value, Type);
-				var newValue = ctx.Adapter.Convert (ctx, vref.Value, Type);
-				SetValue (ctx, newValue);
-			} catch (Exception ex) {
-				Context.WriteDebuggerError (ex);
-				Context.WriteDebuggerOutput ("Value assignment failed: {0}: {1}\n", ex.GetType (), ex.Message);
-			}
-			
-			try {
-				return Context.Evaluator.TargetObjectToExpression (Context, Value);
-			} catch (Exception ex) {
-				Context.WriteDebuggerError (ex);
-				Context.WriteDebuggerOutput ("Value assignment failed: {0}: {1}\n", ex.GetType (), ex.Message);
-			}
-			
-			return null;
+			Context.WaitRuntimeInvokes ();
+			var ctx = GetContext (options);
+			return ValueModificationUtil.ModifyValue (ctx, value, Type, newVal => SetValue (ctx, newVal));
 		}
 
 		object IObjectValueSource.GetRawValue (ObjectPath path, EvaluationOptions options)