Bug 44266 - Unable to change variable values whilst debugging

Author: David Karlaš

Mono.Debugger.Soft/Mono.Debugger.Soft/Connection.cs

@@ -421,7 +421,7 @@ public abstract class Connection
 		 * with newer runtimes, and vice versa.
 		 */
 		internal const int MAJOR_VERSION = 2;
-		internal const int MINOR_VERSION = 43;
+		internal const int MINOR_VERSION = 44;
 
 		enum WPSuspendPolicy {
 			NONE = 0,
@@ -591,6 +591,7 @@ enum CmdStackFrame {
 			GET_THIS = 2,
 			SET_VALUES = 3,
 			GET_DOMAIN = 4,
+			SET_THIS = 5,
 		}
 
 		enum CmdArrayRef {
@@ -2400,6 +2401,10 @@ internal long StackFrame_GetDomain (long thread_id, long id) {
 			return SendReceive (CommandSet.STACK_FRAME, (int)CmdStackFrame.GET_DOMAIN, new PacketWriter ().WriteId (thread_id).WriteId (id)).ReadId ();
 		}
 
+		internal void StackFrame_SetThis (long thread_id, long id, ValueImpl value) {
+			SendReceive (CommandSet.STACK_FRAME, (int)CmdStackFrame.SET_THIS, new PacketWriter ().WriteId (thread_id).WriteId (id).WriteValue (value));
+		}
+
 		/*
 		 * ARRAYS
 		 */

Mono.Debugger.Soft/Mono.Debugger.Soft/StackFrame.cs

@@ -178,6 +178,15 @@ public Value GetThis () {
 			return vm.DecodeValue (vm.conn.StackFrame_GetThis (thread.Id, Id));
 		}
 
+		// Since protocol version 2.44
+		public void SetThis (Value value) {
+			if (value == null)
+				throw new ArgumentNullException ("value");
+			if (Method.IsStatic || !Method.DeclaringType.IsValueType)
+				throw new InvalidOperationException ("The frame's method needs to be a valuetype instance method.");
+			vm.conn.StackFrame_SetThis (thread.Id, Id, vm.EncodeValue (value));
+		}
+
 		public void SetValue (LocalVariable var, Value value) {
 			if (var == null)
 				throw new ArgumentNullException ("var");

Mono.Debugger.Soft/Mono.Debugger.Soft/VirtualMachine.cs

@@ -665,7 +665,7 @@ internal Value[] DecodeValues (ValueImpl[] values, Dictionary<int, Value> parent
 			return res;
 		}
 
-		internal ValueImpl EncodeValue (Value v) {
+		internal ValueImpl EncodeValue (Value v, List<Value> duplicates = null) {
 			if (v is PrimitiveValue) {
 				object val = (v as PrimitiveValue).Value;
 				if (val == null)
@@ -675,16 +675,22 @@ internal ValueImpl EncodeValue (Value v) {
 			} else if (v is ObjectMirror) {
 				return new ValueImpl { Type = ElementType.Object, Objid = (v as ObjectMirror).Id };
 			} else if (v is StructMirror) {
-				return new ValueImpl { Type = ElementType.ValueType, Klass = (v as StructMirror).Type.Id, Fields = EncodeValues ((v as StructMirror).Fields) };
+				if (duplicates == null)
+					duplicates = new List<Value> ();
+				if (duplicates.Contains (v))
+					return new ValueImpl { Type = (ElementType)ValueTypeId.VALUE_TYPE_ID_NULL, Objid = 0 };
+				duplicates.Add (v);
+
+				return new ValueImpl { Type = ElementType.ValueType, Klass = (v as StructMirror).Type.Id, Fields = EncodeValues ((v as StructMirror).Fields, duplicates) };
 			} else {
 				throw new NotSupportedException ();
 			}
 		}
 
-		internal ValueImpl[] EncodeValues (IList<Value> values) {
+		internal ValueImpl[] EncodeValues (IList<Value> values, List<Value> duplicates = null) {
 			ValueImpl[] res = new ValueImpl [values.Count];
 			for (int i = 0; i < values.Count; ++i)
-				res [i] = EncodeValue (values [i]);
+				res [i] = EncodeValue (values [i], duplicates);
 			return res;
 		}
 

Mono.Debugging.Soft/SoftDebuggerAdaptor.cs

@@ -774,10 +774,14 @@ IEnumerable<ValueReference> GetHoistedLocalVariables (SoftEvaluationContext cx,
 						var name = GetHoistedIteratorLocalName (field, cx);
 
 						if (!string.IsNullOrEmpty (name))
-							list.Add (new FieldValueReference (cx, field, val, type, name, ObjectValueFlags.Variable));
+							list.Add (new FieldValueReference (cx, field, val, type, name, ObjectValueFlags.Variable) {
+								ParentSource = vthis
+							});
 					}
 				} else if (!field.Name.Contains ("$")) {
-					list.Add (new FieldValueReference (cx, field, val, type, field.Name, ObjectValueFlags.Variable));
+					list.Add (new FieldValueReference (cx, field, val, type, field.Name, ObjectValueFlags.Variable) {
+						ParentSource = vthis
+					});
 				}
 			}
 

Mono.Debugging.Soft/ThisValueReference.cs

@@ -60,7 +60,10 @@ public override object Value {
 				return value;
 			}
 			set {
-				throw new NotSupportedException ();
+				if (frame.VirtualMachine.Version.AtLeast (2, 44)) {
+					this.value = (Value)value;
+					frame.SetThis ((Value)value);
+				}
 			}
 		}
 

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

@@ -243,7 +243,7 @@ public virtual IEnumerable<ValueReference> GetChildReferences (EvaluationOptions
 			return new ValueReference [0];
 		}
 
-		public IObjectSource ParentSource { get; internal set; }
+		public IObjectSource ParentSource { get; set; }
 
 		protected EvaluationContext GetChildrenContext (EvaluationOptions options)
 		{