Dialog focus restoration doesn't work on mat-menu-items

[calebegg]

If you trigger a dialog from a mat-menu-item's click handler, the focused item is the mat-menu-item itself. This gets saved in _elementFocusedBeforeDialogWasOpened. But that element is gone from the DOM when the dialog is closed, so focus is restored to the body.

It would be cool if the dialog could somehow keep track of the fact that it was a transient menu item that was focused, and focus ought to go back to the menu's trigger instead.

Waiting a tick before opening the dialog fixes it, because the menu itself focuses the trigger before the dialog opens, so it gets the right element ref.

[jelbourn]

We've updated our documentation with guidance around manually restoring focus for this case in #21011. I'm going to leave this issue open since we might explore more ways to do this in the future, but we aren't taking any further action in the short term.

[michaelenglo]

One trick you can try is to manually close the mat-menu so it restores the focus to the trigger right before opening the dialog.

@ViewChildren(MatMenuTrigger) menuTrigger: MatMenuTrigger;

onMenuItemClick() {
    // Doing this first before potentially opening any dialogs to put the focus back to the trigger.
    if (menuTrigger.menuOpen) trigger.closeMenu();
    
    this.dialog.open(FooDialog);
}