DataContext bindings in ControlTemplate leak memory

[BAndysc]

Describe the bug

Having a datacontext binding in a ControlTemplate, like:

<TabStrip.Styles>
  <Style Selector="TabStripItem">
    <Setter Property="Template">
      <ControlTemplate>
        <DockPanel>
          <TextBlock x:DataType="avaloniaBugs:BigFileViewModel" Text="{CompiledBinding Title}" />
        </DockPanel>
      </ControlTemplate>
    </Setter>
  </Style>

leads to memory leaks. This can be workaround with an ItemTemplate, I think this use case should either work as expected or it should be be completely disallowed with a xaml compiler error.

To Reproduce

1. git clone https://github.com/BAndysc/avalonia-bugs-repro
2. git checkout bug_template_binding_leak
3. Run the app with a memory profiler, i.e. dotMemory
4. Press "New Tab"
5. Close the tabs
6. Observe the memory is not freed

Without bindings in Template:
Open MainWindow.axaml, comment lines https://github.com/BAndysc/avalonia-bugs-repro/blob/bug_template_binding_leak/AvaloniaBugs/MainWindow.axaml#L25-L26

Do the same steps - memory will be freed now.

Expected behavior

No response

Avalonia version

0.10, 11.0.x and latest nightly

OS

No response

Additional context

No response

[MrJul]

There are two leaks here:

• The first one and main one leaking all items is from the binding to #Root in https://github.com/BAndysc/avalonia-bugs-repro/blob/bug_template_binding_leak/AvaloniaBugs/MainWindow.axaml#L25 and is fixed in Fix binding related memory leaks #15485

• The second one is leaking only the last selected item and is fixed in fix: SelectingItemsControl Selection memory Leak #15446

[BAndysc]

With those two PRs it works much better now. There is, however, still one small "semi-leak"

1. Press Add Tab three times
2. Press Close All Tabs

One of the tabs will not be freed, until a new tab is opened

SelectedValue is not cleared, even tho SelectedItem was set to null

Of course this is not as serious as the previous leak, since upon opening a new tab, SelectedValue will be updated again and the old tab will be freed.

[MrJul]

The remaining problem here is that SelectionChanged isn't raised when the items collection is cleared (despite SelectedItem being changed). Because of that issue, the handler setting SelectedValue isn't being called.

[workgroupengineering]

@MrJul another unhandled scenario from this example is this #15455. Do I create a new issue?