Remove from logical children and clear item container on reset

[Meloman19]

What does the pull request do?

On collection reset remove from logical children and clear container (similarly like OnItemsChanged.Remove)

What is the current behavior?

Currently on collection reset removing from logical children happen after checking for ItemIsOwnContainer. And the container is not cleared at all.

[avaloniaui-bot]

You can test this PR using the following package version. 11.2.999-cibuild0048706-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[cla-avalonia]

• All contributors have signed the CLA.

[Meloman19]

@cla-avalonia agree

[jp2masa]

This code was already here, but it looks a bit suspicious. It checks if the ItemIsOwnContainerProperty is not set, but it should also check if it's set to false, I think?

EDIT: I see, it's a private property and it's only set to true, so it's probably done like this for performance reasons.

[Meloman19]

I think it's just mistake made due to inattention. You can look at the local method Remove in OnItemsChanged at this file. When item removed from the list, it is always remove from logical children and IsOwn property used only for clearing.

[pavelovcharov]

A simple test for this case could be added here

Avalonia/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs

Line 978 in 0063a5e

        [Fact]
        public void ContainerClearing_Is_Raised_When_ItemsSource_Is_Cleared()
        {
            using var app = Start();
            var itemsSource = new ObservableCollection<object> { "Foo", "Bar", "Baz" };
            var target = CreateTarget(itemsSource: itemsSource);

            var expectedContainers = itemsSource.Select(x => target.ContainerFromItem(x)).ToArray();  
            var actualContainers = new List<Control>();
            var raised = 0;
            
            target.ContainerClearing += (s, e) =>
            {
                actualContainers.Add(e.Container);
                ++raised;
            };
            
            itemsSource.Clear();
            
            Assert.Equal(3, raised);
            Assert.Equal(expectedContainers, actualContainers);
        }

[Meloman19]

@pavelovcharov Thanks! I forgot about the test.

[avaloniaui-bot]

You can test this PR using the following package version. 11.2.999-cibuild0048726-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[grokys]

Sorry about the delay in getting to this, looks good to me, thank you!