Check that list and its direct children are not empty

Issue:
https://github.com/genenetwork/gn-gemtext-threads/blob/main/topics/gn1-migration-to-gn2/clustering.gmi

* Add code to pass the test that the list/tuple passed to `nearest' and its
  direct children lists/tuples are not empty.

1 files changed, 8 insertions, 0 deletions

diff --git a/gn3/computations/slink.py b/gn3/computations/slink.py
index d6f6028..704a0f4 100644
--- a/gn3/computations/slink.py
+++ b/gn3/computations/slink.py
@@ -12,6 +12,14 @@ def raise_valueerror_if_data_is_not_lists_or_tuples(lists):
     if (not is_list_or_tuple(lists)) or (not all(map(is_list_or_tuple, lists))):
         raise ValueError("Expected list or tuple")
 
+def raise_valueerror_if_lists_empty(lists):
+    """Check that the list and its direct children are not empty."""
+    def empty(lst):
+        return len(lst) == 0
+    if (empty(lists)) or not all(map(lambda x: not empty(x), lists)):
+        raise ValueError("List/Tuple should NOT be empty!")
+
 def nearest(lists, i, j):
     raise_valueerror_if_data_is_not_lists_or_tuples(lists)
+    raise_valueerror_if_lists_empty(lists)
     return None