TreeNode memory leak and multiple getChildren calls

Steps to reproduce

This issue can be reproduced with release 7.0.1 of this GitHub repository.

1. Run npm run example:cli:win
2. In Chrome, open http://localhost:4200
3. Open the browser console.
4. Expand “asyncroot”. Observe that the console shows one “toggleExpanded” event and one “loadNodeChildren” event, which is expected.
5. (Important) Refresh the browser to clear the asynchronously loaded children.
6. Click the “Add Node” button ten times.
7. (Optional) Use the browser developer tools to try to force garbage collection.
8. Expand “asyncroot”. Observe that the console shows one “toggleExpanded” event and eleven “loadNodeChildren” event.

Observations

1. Every time TreeModel.update() is called a new TreeNode object is created for every node in the tree. The TreeNode objects never seem to be destroyed, resulting in a significant memory leak.
2. On expanding a node that loads children asynchronously, all the TreeNode objects that have ever been created for that node will call getChildren. If getChildren makes a HTTP request this will result in multiple identical requests being issued in rapid succession.

This makes the component virtually unusable in any scenario that involves updating a tree with lazy loading.

[kareljuricka]

Great work with memory leak fixes. It’s possible to release new version from this updated master?

[adamkleingit]

Published in 8.0.1.

Thanks for the PR!