Events and registered commands on TreeView are unreliable when refreshing treeview

[FPtje]

Does this issue occur when all extensions are disabled?: No/unknown, because I need an extension to show the behavior in the first place.

• VS Code Version: vscode-1.68.1
• OS Version: NixOS, with nixpkgs at revision 95e79164be1f7d883ed9ffda8b7d4ad3a17e6c1e. Also seen with Ubuntu 20.04.

Steps to Reproduce:

• Create an extension with a tree view as per the basic instructions at https://code.visualstudio.com/api/extension-guides/tree-view
• Refresh the tree very often, by using some function like this (this makes it easier to reproduce):

  async function refreshVeryOften(provider: NodeDependenciesProvider) {
      while (true) {
          await new Promise(f => setTimeout(f, 10)); // Wait 10ms, or some other small amount of time
          provider._onDidChangeTreeData.fire();
      }
  }

• Register some view actions, as per https://code.visualstudio.com/api/extension-guides/tree-view#view-actions
  • Let's say we add the nodeDependencies.editEntry command and add it to the view/item/context, as per the example.
• Register an onDidExpandElement and onDidCollapseElement listener that just run console.log. e.g.:

  treeView.onDidExpandElement(event => console.log("onDidExpandElement", event));
  treeView.onDidCollapseElement(event => console.log("onDidCollapseElement", event));

• Start VS Code with the extension
• Try to run the added view action a couple of times
• Try to expand/collapse some tree items. It might take some times to reproduce

Expected results

Despite the refreshes, I would expect the onDidExpandElement and onDidCollapseElement listeners to run and console.log the event. I would also expect the nodeDependencies.editEntry command to always run, and the function is passed a TreeItem.

Actual result

• onDidExpandElement often does not get called, even though in the UI, I see that the tree view item is expanded
• onDidCollapseElement often does not get called, even though in the UI, I see that the tree view item is collapsed
• The nodeDependencies.editEntry registered command sometimes gets called with no arguments, i.e. no TreeItem is passed.

Video example

This is in a different project, namely my Semaphore CI extension. Note that I have set the refresh delay to 2 seconds (2000ms).

Same for collapsing/expanding events. In the video you can see the element being expanded and collapsed, but not every change in the UI is shown in the events.

Speculated cause

I think some part of the tree view is removed before the new one is finished rendering, during a refresh. Either way it seems like some race/timing condition, because it sometimes happens and sometimes doesn't, even though the code path on the extension side should be exactly the same.

[alexr00]

I think some part of the tree view is removed before the new one is finished rendering, during a refresh.

When I investigated this before, I saw that this is exactly what happens.