Correctly detect max depth of NestedSelect if level is empty

panel/tests/widgets/test_select.py

@@ -300,6 +300,15 @@ def test_nested_select_init_empty(document, comm):
  assert select.options is None
  assert select.levels == []
 
+def test_nested_select_max_depth_empty_first_sublevel(document, comm):
+ select = NestedSelect(options={'foo': ['a', 'b'], 'bar': []})
+
+ assert select._max_depth == 2
+
+def test_nested_select_max_depth_empty_second_sublevel(document, comm):
+ select = NestedSelect(options={'foo': {'0': ['a', 'b'], '1': []}, 'bar': {'0': []}})
+
+ assert select._max_depth == 3
 
 def test_nested_select_init_levels(document, comm):
  options = {
@@ -500,7 +509,7 @@ def test_nested_select_partial_options_set(document, comm):
  select.options = {"Ben": []}
  assert select._widgets[0].value == 'Ben'
  assert select._widgets[0].visible
- assert select.value == {0: 'Ben'}
+ assert select.value == {0: 'Ben', 1: None}
 
 
 def test_nested_select_partial_value_init(document, comm):

panel/widgets/select.py

@@ -422,19 +422,11 @@ def _uses_callable(self, d):
  return False
 
  def _find_max_depth(self, d, depth=1):
- if d is None or len(d) == 0:
- return 0
- elif not isinstance(d, dict):
- return depth
-
+ if isinstance(d, list) or d is None:
+ return depth-1
  max_depth = depth
  for value in d.values():
- if isinstance(value, dict):
- max_depth = max(max_depth, self._find_max_depth(value, depth + 1))
- # dict means it's a level, so it's not the last level
- # list means it's a leaf, so it's the last level
- if isinstance(value, list) and len(value) == 0 and max_depth > 0:
- max_depth -= 1
+ max_depth = max(max_depth, self._find_max_depth(value, depth + 1))
  return max_depth
 
  def _resolve_callable_options(self, i, options) -> dict | list: