Changes after review

NOTICE.md

@@ -81,14 +81,14 @@ A "contributor" is any person that distributes its contribution under this licen
 
 https://github.com/wayland-project/wayland-protocols
 
-Copyright © 2008-2013 Kristian Høgsberg
-Copyright © 2010-2013 Intel Corporation
-Copyright © 2013      Rafael Antognolli
-Copyright © 2013      Jasper St. Pierre
-Copyright © 2014      Jonas Ådahl
-Copyright © 2014      Jason Ekstrand
-Copyright © 2014-2015 Collabora, Ltd.
-Copyright © 2015      Red Hat Inc.
+Copyright © 2008-2013 Kristian Høgsberg
+Copyright © 2010-2013 Intel Corporation
+Copyright © 2013      Rafael Antognolli
+Copyright © 2013      Jasper St. Pierre
+Copyright © 2014      Jonas Ådahl
+Copyright © 2014      Jason Ekstrand
+Copyright © 2014-2015 Collabora, Ltd.
+Copyright © 2015      Red Hat Inc.
 
 Permission is hereby granted, free of charge, to any person obtaining a
 copy of this software and associated documentation files (the "Software"),
@@ -140,7 +140,7 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 https://github.com/toptensoftware/RichTextKit
 
-Copyright © 2019 Topten Software. All Rights Reserved.
+Copyright © 2019 Topten Software. All Rights Reserved.
 
 Licensed under the Apache License, Version 2.0 (the "License"); you may 
 not use this product except in compliance with the License. You may obtain 
@@ -334,3 +334,31 @@ https://github.com/flutter/flutter
 //ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 //(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 //SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+# Reactive Extensions
+
+https://github.com/dotnet/reactive
+
+The MIT License (MIT)
+
+Copyright (c) .NET Foundation and Contributors
+
+All rights reserved.
+
+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.

src/Avalonia.Base/Data/Core/ExpressionObserver.cs

@@ -104,7 +104,7 @@ namespace Avalonia.Data.Core
         public ExpressionObserver(
             Func<object?> rootGetter,
             ExpressionNode node,
-            IObservable<object> update,
+            IObservable<ValueTuple> update,
             string? description)
         {
             Description = description;
@@ -171,7 +171,7 @@ namespace Avalonia.Data.Core
         public static ExpressionObserver Create<T, U>(
             Func<T> rootGetter,
             Expression<Func<T, U>> expression,
-            IObservable<object> update,
+            IObservable<ValueTuple> update,
             bool enableDataValidation = false,
             string? description = null)
         {

src/Avalonia.Base/Reactive/Operators/Sink.cs

@@ -3,6 +3,8 @@ using System.Threading;
 
 namespace Avalonia.Reactive.Operators;
 
+// Code based on https://github.com/dotnet/reactive/blob/main/Rx.NET/Source/src/System.Reactive/Internal/Sink.cs
+
 internal abstract class Sink<TTarget> : IDisposable
 {
     private IDisposable? _upstream;

src/Markup/Avalonia.Markup/Data/BindingBase.cs

@@ -252,9 +252,8 @@ namespace Avalonia.Data
                 }).Switch();
         }
 
-        private class UpdateSignal : SingleSubscriberObservableBase<object>
+        private class UpdateSignal : SingleSubscriberObservableBase<ValueTuple>
         {
-            private static readonly object s_val = new(); 
             private readonly AvaloniaObject _target;
             private readonly AvaloniaProperty _property;
 
@@ -278,7 +277,7 @@ namespace Avalonia.Data
             {
                 if (e.Property == _property)
                 {
-                    PublishNext(s_val);
+                    PublishNext(default);
                 }
             }
         }

src/Markup/Avalonia.Markup/Markup/Parsers/ExpressionObserverBuilder.cs

@@ -63,7 +63,7 @@ namespace Avalonia.Markup.Parsers
         public static ExpressionObserver Build(
             Func<object> rootGetter,
             string expression,
-            IObservable<object> update,
+            IObservable<ValueTuple> update,
             bool enableDataValidation = false,
             string? description = null,
             Func<string, string, Type>? typeResolver = null)

tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Lifetime.cs

@@ -41,7 +41,7 @@ namespace Avalonia.Base.UnitTests.Data.Core
         [Fact]
         public void Should_Complete_When_Update_Observable_Completes()
         {
-            var update = new Subject<object>();
+            var update = new Subject<ValueTuple>();
             var target = ExpressionObserver.Create(() => 1, o => o, update);
             var completed = false;
 
@@ -54,7 +54,7 @@ namespace Avalonia.Base.UnitTests.Data.Core
         [Fact]
         public void Should_Complete_When_Update_Observable_Errors()
         {
-            var update = new Subject<object>();
+            var update = new Subject<ValueTuple>();
             var target = ExpressionObserver.Create(() => 1, o => o, update);
             var completed = false;
 
@@ -87,7 +87,7 @@ namespace Avalonia.Base.UnitTests.Data.Core
         public void Should_Unsubscribe_From_Update_Observable()
         {
             var scheduler = new TestScheduler();
-            var update = scheduler.CreateColdObservable<object>();
+            var update = scheduler.CreateColdObservable<ValueTuple>();
             var data = new { Foo = "foo" };
             var target = ExpressionObserver.Create(() => data, o => o.Foo, update);
             var result = new List<object>();

tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Property.cs

@@ -359,14 +359,14 @@ namespace Avalonia.Base.UnitTests.Data.Core
         public void Empty_Expression_Should_Track_Root()
         {
             var data = new Class1 { Foo = "foo" };
-            var update = new Subject<object>();
+            var update = new Subject<ValueTuple>();
             var target = ExpressionObserver.Create(() => data.Foo, o => o, update);
             var result = new List<object>();
 
             target.Subscribe(x => result.Add(x));
 
             data.Foo = "bar";
-            update.OnNext(Unit.Default);
+            update.OnNext(default);
 
             Assert.Equal(new[] { "foo", "bar" }, result);
 
@@ -533,15 +533,15 @@ namespace Avalonia.Base.UnitTests.Data.Core
             var first = new Class1 { Foo = "foo" };
             var second = new Class1 { Foo = "bar" };
             var root = first;
-            var update = new Subject<object>();
+            var update = new Subject<ValueTuple>();
             var target = ExpressionObserver.Create(() => root, o => o.Foo, update);
             var result = new List<object>();
             var sub = target.Subscribe(x => result.Add(x));
 
             root = second;
-            update.OnNext(Unit.Default);
+            update.OnNext(default);
             root = null;
-            update.OnNext(Unit.Default);
+            update.OnNext(default);
 
             Assert.Equal(
                 new object[]
@@ -640,7 +640,7 @@ namespace Avalonia.Base.UnitTests.Data.Core
         public void RootGetter_Is_Reevaluated_On_Subscribe()
         {
             var data = "foo";
-            var target = new ExpressionObserver(() => data, new EmptyExpressionNode(), new Subject<object>(), null);
+            var target = new ExpressionObserver(() => data, new EmptyExpressionNode(), new Subject<ValueTuple>(), null);
             var result = new List<object>();
             var sub = target.Subscribe(x => result.Add(x));