Fix LocalValue bindings during batch update.

LocalValue bindings are special case due to their interaction with the local value set by a non-binding.

src/Avalonia.Base/PropertyStore/PriorityValue.cs

@@ -27,6 +27,7 @@ namespace Avalonia.PropertyStore
         private Optional<T> _localValue;
         private Optional<T> _value;
         private bool _isCalculatingValue;
+        private bool _batchUpdate;
 
         public PriorityValue(
             IAvaloniaObject owner,
@@ -93,6 +94,8 @@ namespace Avalonia.PropertyStore
 
         public void BeginBatchUpdate()
         {
+            _batchUpdate = true;
+
             foreach (var entry in _entries)
             {
                 (entry as IBatchUpdate)?.BeginBatchUpdate();
@@ -101,6 +104,8 @@ namespace Avalonia.PropertyStore
 
         public void EndBatchUpdate()
         {
+            _batchUpdate = false;
+
             foreach (var entry in _entries)
             {
                 (entry as IBatchUpdate)?.EndBatchUpdate();
@@ -165,6 +170,17 @@ namespace Avalonia.PropertyStore
             var binding = new BindingEntry<T>(_owner, Property, source, priority, this);
             var insert = FindInsertPoint(binding.Priority);
             _entries.Insert(insert, binding);
+
+            if (_batchUpdate)
+            {
+                binding.BeginBatchUpdate();
+                
+                if (priority == BindingPriority.LocalValue)
+                {
+                    binding.Start(ignoreBatchUpdate: true);
+                }
+            }
+
             return binding;
         }
 

src/Avalonia.Base/ValueStore.cs

@@ -313,6 +313,11 @@ namespace Avalonia
             if (slot is IPriorityValueEntry<T> e)
             {
                 priorityValue = new PriorityValue<T>(_owner, property, this, e);
+
+                if (_batchUpdate is object)
+                {
+                    priorityValue.BeginBatchUpdate();
+                }
             }
             else if (slot is PriorityValue<T> p)
             {

tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_BatchUpdate.cs

@@ -233,40 +233,72 @@ namespace Avalonia.Base.UnitTests
         }
 
         [Fact]
-        public void Bindings_Should_Not_Be_Subscribed_During_Batch_Update()
+        public void LocalValue_Bindings_Should_Be_Subscribed_During_Batch_Update()
         {
             var target = new TestClass();
             var observable1 = new TestObservable<string>("foo");
             var observable2 = new TestObservable<string>("bar");
-            var observable3 = new TestObservable<string>("baz");
+            var raised = new List<AvaloniaPropertyChangedEventArgs>();
+
+            target.PropertyChanged += (s, e) => raised.Add(e);
 
+            // We need to subscribe to LocalValue bindings even if we've got a batch operation
+            // in progress because otherwise we don't know whether the binding or a subsequent
+            // SetValue with local priority will win. Notifications however shouldn't be sent.
             target.BeginBatchUpdate();
             target.Bind(TestClass.FooProperty, observable1, BindingPriority.LocalValue);
             target.Bind(TestClass.FooProperty, observable2, BindingPriority.LocalValue);
-            target.Bind(TestClass.FooProperty, observable3, BindingPriority.Style);
+
+            Assert.Equal(1, observable1.SubscribeCount);
+            Assert.Equal(1, observable2.SubscribeCount);
+            Assert.Empty(raised);
+        }
+
+        [Fact]
+        public void Style_Bindings_Should_Not_Be_Subscribed_During_Batch_Update()
+        {
+            var target = new TestClass();
+            var observable1 = new TestObservable<string>("foo");
+            var observable2 = new TestObservable<string>("bar");
+
+            target.BeginBatchUpdate();
+            target.Bind(TestClass.FooProperty, observable1, BindingPriority.Style);
+            target.Bind(TestClass.FooProperty, observable2, BindingPriority.StyleTrigger);
 
             Assert.Equal(0, observable1.SubscribeCount);
             Assert.Equal(0, observable2.SubscribeCount);
-            Assert.Equal(0, observable3.SubscribeCount);
         }
 
         [Fact]
-        public void Active_Binding_Should_Be_Subscribed_After_Batch_Uppdate()
+        public void Active_Style_Binding_Should_Be_Subscribed_After_Batch_Uppdate_1()
         {
             var target = new TestClass();
             var observable1 = new TestObservable<string>("foo");
             var observable2 = new TestObservable<string>("bar");
-            var observable3 = new TestObservable<string>("baz");
 
             target.BeginBatchUpdate();
-            target.Bind(TestClass.FooProperty, observable1, BindingPriority.LocalValue);
-            target.Bind(TestClass.FooProperty, observable2, BindingPriority.LocalValue);
-            target.Bind(TestClass.FooProperty, observable3, BindingPriority.Style);
+            target.Bind(TestClass.FooProperty, observable1, BindingPriority.Style);
+            target.Bind(TestClass.FooProperty, observable2, BindingPriority.Style);
             target.EndBatchUpdate();
 
             Assert.Equal(0, observable1.SubscribeCount);
             Assert.Equal(1, observable2.SubscribeCount);
-            Assert.Equal(0, observable3.SubscribeCount);
+        }
+
+        [Fact]
+        public void Active_Style_Binding_Should_Be_Subscribed_After_Batch_Uppdate_2()
+        {
+            var target = new TestClass();
+            var observable1 = new TestObservable<string>("foo");
+            var observable2 = new TestObservable<string>("bar");
+
+            target.BeginBatchUpdate();
+            target.Bind(TestClass.FooProperty, observable1, BindingPriority.StyleTrigger);
+            target.Bind(TestClass.FooProperty, observable2, BindingPriority.Style);
+            target.EndBatchUpdate();
+
+            Assert.Equal(1, observable1.SubscribeCount);
+            Assert.Equal(0, observable2.SubscribeCount);
         }
 
         public class TestClass : AvaloniaObject