[Debugger] Fixed tracking of current expressions in Watch Pad

This avoids scenarios where we clear the expressions list thereby
losing all known expressions.

Fixes https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1002638/

Author: jstedfast

main/src/addins/MonoDevelop.Debugger/MonoDevelop.Debugger.csproj

@@ -206,6 +206,7 @@
     <Compile Include="MonoDevelop.Debugger\ObjectValue\Mac\MacDebuggerObjectValueView.cs" />
     <Compile Include="MonoDevelop.Debugger\ObjectValue\Mac\MacDebuggerObjectTypeView.cs" />
     <Compile Include="MonoDevelop.Debugger\ObjectValue\Mac\MacDebuggerObjectPinView.cs" />
+    <Compile Include="MonoDevelop.Debugger\ObjectValue\ExpressionEventArgs.cs" />
   </ItemGroup>
   <ItemGroup Condition="$(OS) != 'Windows_NT'">
     <Compile Include="MonoDevelop.Debugger.VSTextView\ExceptionCaught\ExceptionCaughtProvider.cs" />

main/src/addins/MonoDevelop.Debugger/MonoDevelop.Debugger/ObjectValue/ExpressionEventArgs.cs

@@ -0,0 +1,59 @@
+//
+// ExpressionEventArgs.cs
+//
+// Author:
+//       Jeffrey Stedfast <[email protected]>
+//
+// Copyright (c) 2019 Microsoft Corp.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+using System;
+
+namespace MonoDevelop.Debugger
+{
+	public class ExpressionEventArgs : EventArgs
+	{
+		public ExpressionEventArgs (string expression)
+		{
+			Expression = expression;
+		}
+
+		public string Expression {
+			get; private set;
+		}
+	}
+
+	public class ExpressionChangedEventArgs : EventArgs
+	{
+		public ExpressionChangedEventArgs (string oldExpression, string newExpression)
+		{
+			OldExpression = oldExpression;
+			NewExpression = newExpression;
+		}
+
+		public string OldExpression {
+			get; private set;
+		}
+
+		public string NewExpression {
+			get; private set;
+		}
+	}
+}

main/src/addins/MonoDevelop.Debugger/MonoDevelop.Debugger/ObjectValue/Mac/MacObjectValueTreeView.cs

@@ -818,7 +818,7 @@ bool CanDelete (out bool enabled)
 
 			var selectedRows = SelectedRows;
 			foreach (var row in selectedRows) {
-				var item = (MacObjectValueNode)ItemAtRow ((nint)row);
+				var item = (MacObjectValueNode) ItemAtRow ((nint) row);
 
 				if (!(item.Target.Parent is RootObjectValueNode)) {
 					enabled = false;

main/src/addins/MonoDevelop.Debugger/MonoDevelop.Debugger/ObjectValue/ObjectValueTreeViewController.cs

@@ -300,6 +300,9 @@ void RemoveValue (ObjectValueNode node)
 		{
 			UnregisterNode (node);
 			OnEvaluationCompleted (node, new ObjectValueNode[0]);
+
+			if (AllowWatchExpressions && node.Parent is RootObjectValueNode)
+				ExpressionRemoved?.Invoke (this, new ExpressionEventArgs (node.Name));
 		}
 
 		// TODO: can we improve this
@@ -371,6 +374,10 @@ public bool GetNodeWasExpandedAtLastCheckpoint (ObjectValueNode node)
 
 		#region Expressions
 
+		public event EventHandler<ExpressionEventArgs> ExpressionAdded;
+		public event EventHandler<ExpressionChangedEventArgs> ExpressionChanged;
+		public event EventHandler<ExpressionEventArgs> ExpressionRemoved;
+
 		public void AddExpression (string expression)
 		{
 			if (!AllowWatchExpressions) {
@@ -381,6 +388,8 @@ public void AddExpression (string expression)
 			LoggingService.LogInfo ("Evaluating expression '{0}'", expression);
 			var node = Frame.EvaluateExpression (expression);
 			AddValue (node);
+
+			ExpressionAdded?.Invoke (this, new ExpressionEventArgs (expression));
 		}
 
 		public void AddExpressions (IList<string> expressions)
@@ -391,24 +400,34 @@ public void AddExpressions (IList<string> expressions)
 			if (Frame != null) {
 				var nodes = Frame.EvaluateExpressions (expressions);
 				AddValues (nodes);
+
+				var expressionAdded = ExpressionAdded;
+				if (expressionAdded != null) {
+					foreach (var expression in expressions)
+						expressionAdded (this, new ExpressionEventArgs (expression));
+				}
 			}
 		}
 
 		bool EditExpression (ObjectValueNode node, string newExpression)
 		{
-			if (node.Name == newExpression)
+			var oldExpression = node.Name;
+
+			if (oldExpression == newExpression)
 				return false;
 
 			UnregisterNode (node);
 			if (string.IsNullOrEmpty (newExpression)) {
 				// we want the expression removed from the tree
 				OnEvaluationCompleted (node, new ObjectValueNode[0]);
+				ExpressionRemoved?.Invoke (this, new ExpressionEventArgs (oldExpression));
 				return true;
 			}
 
 			var expressionNode = Frame.EvaluateExpression (newExpression);
 			RegisterNode (expressionNode);
 			OnEvaluationCompleted (node, new ObjectValueNode[] { expressionNode });
+			ExpressionChanged?.Invoke (this, new ExpressionChangedEventArgs (oldExpression, newExpression));
 
 			return true;
 		}

main/src/addins/MonoDevelop.Debugger/MonoDevelop.Debugger/WatchPad.cs

@@ -45,7 +45,11 @@ public class WatchPad : ObjectValuePad, IMementoCapable, ICustomXmlSerializer
 
 		public WatchPad () : base (true)
 		{
-			if (!UseNewTreeView) {
+			if (UseNewTreeView) {
+				controller.ExpressionAdded += OnExpressionAdded;
+				controller.ExpressionChanged += OnExpressionChanged;
+				controller.ExpressionRemoved += OnExpressionRemoved;
+			} else {
 				tree.EnableModelDragDest (DropTargets, Gdk.DragAction.Copy);
 				tree.DragDataReceived += HandleDragDataReceived;
 			}
@@ -80,19 +84,19 @@ public void AddWatch (string expression)
 			}
 		}
 
-		void SaveExpressions ()
-		{
-			expressions.Clear ();
-			expressions.AddRange (controller.GetExpressions ());
-		}
-
 		void RestoreExpressions ()
 		{
-			// remove the expressions because we're going to rebuild them
-			controller.ClearAll ();
+			controller.ExpressionAdded -= OnExpressionAdded;
+
+			try {
+				// remove the expressions because we're going to rebuild them
+				controller.ClearAll ();
 
-			// re-add the expressions which will reevaluate the expressions and repopulate the treeview
-			controller.AddExpressions (expressions);
+				// re-add the expressions which will reevaluate the expressions and repopulate the treeview
+				controller.AddExpressions (expressions);
+			} finally {
+				controller.ExpressionAdded += OnExpressionAdded;
+			}
 		}
 
 		public override void OnUpdateFrame ()
@@ -114,24 +118,43 @@ public override void OnUpdateValues ()
 			}
 		}
 
-		protected override void OnDebuggerResumed (object s, EventArgs a)
+		void OnExpressionAdded (object sender, ExpressionEventArgs e)
 		{
-			// base will clear the controller, which removes all values and expressions
+			LoggingService.LogInfo ("Expression added: {0}", e.Expression);
+			expressions.Add (e.Expression);
+		}
 
-			if (UseNewTreeView && !IsInitialResume)
-				SaveExpressions ();
+		void OnExpressionChanged (object sender, ExpressionChangedEventArgs e)
+		{
+			LoggingService.LogInfo ("Expression changed: '{0}' -> '{1}'", e.OldExpression, e.NewExpression);
+			int index = expressions.IndexOf (e.OldExpression);
 
-			base.OnDebuggerResumed (s, a);
+			if (index != -1) {
+				expressions[index] = e.NewExpression;
+			} else {
+				LoggingService.LogWarning ("Failed to find old expression: {0}", e.OldExpression);
+				expressions.Add (e.NewExpression);
+			}
 		}
 
-		protected override void OnDebuggerStopped (object s, EventArgs a)
+		void OnExpressionRemoved (object sender, ExpressionEventArgs e)
 		{
-			// base will clear the controller, which removes all values and expressions
+			LoggingService.LogInfo ("Expression removed: {0}", e.Expression);
+			if (!expressions.Remove (e.Expression))
+				LoggingService.LogWarning ("Failed to remove expression: {0}", e.Expression);
+		}
 
-			if (UseNewTreeView)
-				SaveExpressions ();
+		public override void Dispose ()
+		{
+			if (UseNewTreeView) {
+				controller.ExpressionAdded -= OnExpressionAdded;
+				controller.ExpressionChanged -= OnExpressionChanged;
+				controller.ExpressionRemoved -= OnExpressionRemoved;
+			} else {
+				tree.DragDataReceived -= HandleDragDataReceived;
+			}
 
-			base.OnDebuggerStopped (s, a);
+			base.Dispose ();
 		}
 
 		#region IMementoCapable implementation