Add items and empty-p

hierarchy.el

@@ -183,10 +183,18 @@ default, SORTFN is `string-lessp'."
 ;; Querying
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
+(defun hierarchy-items (hierarchy)
+  "Return a list of all items of HIERARCHY."
+  (map-keys (hierarchy--seen-items hierarchy)))
+
 (defun hierarchy-has-item (hierarchy item)
   "Return t if HIERARCHY includes ITEM."
   (map-contains-key (hierarchy--seen-items hierarchy) item))
 
+(defun hierarchy-empty-p (hierarchy)
+  "Return t if HIERARCHY is empty."
+  (= 0 (hierarchy-length hierarchy)))
+
 (defun hierarchy-length (hierarchy)
   "Return the number of items in HIERARCHY."
   (hash-table-count (hierarchy--seen-items hierarchy)))

test/hierarchy-test.el

@@ -168,6 +168,12 @@
     (should-error
      (hierarchy--add-relation hierarchy 'bird 'cow #'identity))))
 
+(ert-deftest hierarchy-empty-p-return-non-nil-for-empty ()
+  (should (hierarchy-empty-p (hierarchy-new))))
+
+(ert-deftest hierarchy-empty-p-return-nil-for-non-empty ()
+  (should-not (hierarchy-empty-p (test-helper-animals))))
+
 (ert-deftest hierarchy-length-of-empty-is-0 ()
   (should (equal (hierarchy-length (hierarchy-new)) 0)))
 
@@ -312,6 +318,19 @@
   (let* ((animals (test-helper-animals)))
     (should-not (hierarchy-extract-tree animals 'foobar))))
 
+(ert-deftest hierarchy-items-of-empty-hierarchy-is-empty ()
+  (should (seq-empty-p (hierarchy-items (hierarchy-new)))))
+
+(ert-deftest hierarchy-items-returns-sequence-of-same-length ()
+  (let* ((animals (test-helper-animals))
+         (result (hierarchy-items animals)))
+    (should (= (seq-length result) (hierarchy-length animals)))))
+
+(ert-deftest hierarchy-items-return-all-elements-of-hierarchy ()
+  (let* ((animals (test-helper-animals))
+         (result (hierarchy-items animals)))
+    (should (equal (seq-sort #'string< result) '(animal bird cow dolphin dove pigeon)))))
+
 (ert-deftest hierarchy-labelfn-indent-no-indent-if-0 ()
   (let* ((labelfn-base (lambda (_item _indent) (insert "foo")))
          (labelfn (hierarchy-labelfn-indent labelfn-base)))