bug(MatTree): expandAll() only expand the first level

[BeniFreitag]

Is this a regression?

• Yes, this behavior used to work in the previous version

The previous version in which this bug was not present was

17.x

Description

Reopen Issue #29865. CDK/Material: 19.1.2 contains a fix #30226 but the issue still persists.

The method expandAll() of MatTree expands only the first level of a deeply nested tree. On deprecated MatTreeControl, the same method was able to expand the entire tree without problems.

WORKAROUND:

this.dataSource.forEach(node => this.tree.expandDescendants(node));

Reproduction

StackBlitz link:

• Flat nodes: https://stackblitz.com/edit/jfoxsvj4?file=src%2Fexample%2Ftree-flat-child-accessor-overview-example.ts
• Nested nodes: https://stackblitz.com/edit/r8azqcn7?file=src%2Fexample%2Ftree-nested-child-accessor-overview-example.ts

Steps to reproduce:

1. Open the demos.
2. The tree is partially expanded
3. Edit the demo and enable the workaround on the ngAfterViewInit callback.
4. The tree is now fully expanded.

Expected Behavior

MatTree's expandAll() should expand all nodes.

Actual Behavior

Only the first level nodes are expanded.

Environment

• Angular: 19.1.2
• CDK/Material: 19.1.2
• Browser(s): Chrome
• Operating System (e.g. Windows, macOS, Ubuntu): Windows

[JonasMa]

I'm having the same problem. Interestingly it works when calling it after a timeout of > 200ms in the ngAfterViewInit.

I'm using Angular 19.1.4 and Material 19.1.2.

[WwwHhhYran]

I'm having the same problem, and the previous bugfix(#30226 ) has not solved this issue. Is there anyone out there to fix this please?

Also, I can't understand why TreeControl will be deprecated, deprecating TreeControl makes it impossible to control the state of the tree before initializing the view, and I think integrating all the methods from TreeControl into Tree will make custom components less flexible