This fixes a typo in one of the tests of Hierarchy which was causing
the test to fail.
* test/lisp/emacs-lisp/hierarchy-tests.el (hierarchy-delayed-add-trees):
Fix typo.
This adds an option to allow callers to specify that computing
the children of the hierarchy should be delayed to when the
user calls for them, by utilizing the tree-widget :expander
property.
* lisp/emacs-lisp/hierarchy.el (hierarchy-add-tree)
(hierarchy-add-trees): Add parameter 'delay-children-p'.
* lisp/emacs-lisp/hierarchy.el
(hierarchy--create-delayed-tree-widget): Add function.
* lisp/emacs-lisp/hierarchy.el (hierarchy-convert-to-tree-widget):
Utilize ':expander' if delaying children. (Bug#55900)
* test/lisp/emacs-lisp/hierarchy-tests.el: Add tests for
delayed-children functionality.