fix hierarchical typing edge case (#1574)

predicators/utils.py

@@ -2806,9 +2806,17 @@ def create_pddl_domain(operators: Collection[NSRTOrSTRIPSOperator],
         for parent_type in sorted(parent_to_children_types):
             child_types = parent_to_children_types[parent_type]
             if not child_types:
-                continue
-            child_type_str = " ".join(t.name for t in child_types)
-            types_str += f"\n    {child_type_str} - {parent_type.name}"
+                # Special case: type has no children and also does not appear
+                # as a child of another type.
+                is_child_type = any(
+                    parent_type in children
+                    for children in parent_to_children_types.values())
+                if not is_child_type:
+                    types_str += f"\n    {parent_type.name}"
+                # Otherwise, the type will appear as a child elsewhere.
+            else:
+                child_type_str = " ".join(t.name for t in child_types)
+                types_str += f"\n    {child_type_str} - {parent_type.name}"
     ops_lst = sorted(operators)
     preds_str = "\n    ".join(pred.pddl_str() for pred in preds_lst)
     ops_strs = "\n\n  ".join(op.pddl_str() for op in ops_lst)

tests/test_utils.py

@@ -2318,12 +2318,16 @@ def test_create_pddl():
     env = ProceduralTasksSpannerPDDLEnv()
     nsrts = get_gt_nsrts(env.get_name(), env.predicates,
                          get_gt_options(env.get_name()))
-    domain_str = utils.create_pddl_domain(nsrts, env.predicates, env.types,
+    # Test case where there is a special type with no parents or children.
+    monkey_type = Type("monkey", [])
+    types = env.types | {monkey_type}
+    domain_str = utils.create_pddl_domain(nsrts, env.predicates, types,
                                           "spanner")
     assert domain_str == """(define (domain spanner)
   (:requirements :typing)
   (:types 
     man nut spanner - locatable
+    monkey
     locatable location - object)
 
   (:predicates