Make sure new value is returned.

When a property value is set, if a new value isn't notified via INPC,
then send the new value after the set succeeds.

src/Markup/Avalonia.Markup/Data/Plugins/InpcPropertyAccessorPlugin.cs

@@ -54,6 +54,7 @@ namespace Avalonia.Markup.Data.Plugins
         {
             private readonly WeakReference _reference;
             private readonly PropertyInfo _property;
+            private bool _eventRaised;
 
             public Accessor(WeakReference reference,  PropertyInfo property)
             {
@@ -79,7 +80,14 @@ namespace Avalonia.Markup.Data.Plugins
             {
                 if (_property.CanWrite)
                 {
+                    _eventRaised = false;
                     _property.SetValue(_reference.Target, value);
+
+                    if (!_eventRaised)
+                    {
+                        SendCurrentValue();
+                    }
+
                     return true;
                 }
 
@@ -90,6 +98,7 @@ namespace Avalonia.Markup.Data.Plugins
             {
                 if (e.PropertyName == _property.Name || string.IsNullOrEmpty(e.PropertyName))
                 {
+                    _eventRaised = true;
                     SendCurrentValue();
                 }
             }
@@ -134,16 +143,6 @@ namespace Avalonia.Markup.Data.Plugins
                         nameof(inpc.PropertyChanged),
                         this);
                 }
-                else
-                {
-                    Logger.Information(
-                        LogArea.Binding,
-                        this,
-                        "Bound to property {Property} on {Source} which does not implement INotifyPropertyChanged",
-                        _property.Name,
-                        _reference.Target,
-                        _reference.Target.GetType());
-                }
             }
         }
     }

tests/Avalonia.Markup.UnitTests/Data/ExpressionObserverTests_Property.cs

@@ -437,6 +437,32 @@ namespace Avalonia.Markup.UnitTests.Data
             }
         }
 
+        [Fact]
+        public void SetValue_Should_Notify_New_Value_With_Inpc()
+        {
+            var data = new Class1();
+            var target = new ExpressionObserver(data, "Foo");
+            var result = new List<object>();
+
+            target.Subscribe(x => result.Add(x));
+            target.SetValue("bar");
+
+            Assert.Equal(new[] { null, "bar" }, result);
+        }
+
+        [Fact]
+        public void SetValue_Should_Notify_New_Value_Without_Inpc()
+        {
+            var data = new Class1();
+            var target = new ExpressionObserver(data, "Bar");
+            var result = new List<object>();
+
+            target.Subscribe(x => result.Add(x));
+            target.SetValue("bar");
+
+            Assert.Equal(new[] { null, "bar" }, result);
+        }
+
         [Fact]
         public void SetValue_Should_Return_False_For_Missing_Object()
         {