Merge branch 'feature/selectionmodel-reset-handling' into feature/selectionmodel-autoselect

src/Avalonia.Controls/SelectionModel.cs

@@ -344,6 +344,7 @@ namespace Avalonia.Controls
         public void Dispose()
         {
             ClearSelection(resetAnchor: false);
+            _rootNode.Cleanup();
             _rootNode.Dispose();
             _selectedIndicesCached = null;
             _selectedItemsCached = null;
@@ -796,6 +797,7 @@ namespace Avalonia.Controls
             }
 
             OnSelectionChanged(e);
+            _rootNode.Cleanup();
         }
 
         private void ApplyAutoSelect()

src/Avalonia.Controls/SelectionNode.cs

@@ -375,6 +375,19 @@ namespace Avalonia.Controls
             }
         }
 
+        public void Cleanup()
+        {
+            foreach (var child in _childrenNodes)
+            {
+                child?.Cleanup();
+
+                if (child?.SelectedCount == 0)
+                {
+                    child.Dispose();
+                }
+            }
+        }
+
         public bool Select(int index, bool select)
         {
             return Select(index, select, raiseOnSelectionChanged: true);
@@ -503,16 +516,6 @@ namespace Avalonia.Controls
             _selectedItems?.Clear();
             SelectedCount = 0;
             AnchorIndex = -1;
-
-            // This will throw away all the children SelectionNodes
-            // causing them to be unhooked from their data source. This
-            // essentially cleans up the tree.
-            foreach (var child in _childrenNodes)
-            {
-                child?.Dispose();
-            }
-
-            _childrenNodes.Clear();
         }
 
         private bool Select(int index, bool select, bool raiseOnSelectionChanged)

tests/Avalonia.Controls.UnitTests/SelectionModelTests.cs

@@ -1185,6 +1185,29 @@ namespace Avalonia.Controls.UnitTests
             Assert.Equal(1, raised);
         }
 
+        [Fact]
+        public void Clearing_Nested_Selection_Raises_SelectionChanged()
+        {
+            var target = new SelectionModel();
+            var raised = 0;
+
+            target.Source = CreateNestedData(1, 2, 3);
+            target.Select(1, 1);
+
+            target.SelectionChanged += (s, e) =>
+            {
+                Assert.Equal(new[] { new IndexPath(1, 1) }, e.DeselectedIndices);
+                Assert.Equal(new object[] { 4 }, e.DeselectedItems);
+                Assert.Empty(e.SelectedIndices);
+                Assert.Empty(e.SelectedItems);
+                ++raised;
+            };
+
+            target.ClearSelection();
+
+            Assert.Equal(1, raised);
+        }
+
         [Fact]
         public void Changing_Source_Raises_SelectionChanged()
         {