ifcopenshell.api.attribute: clear occurrence PredefinedType when type becomes concrete

assign_type() already clears an occurrence's PredefinedType/ObjectType
when it is assigned to a type with a concrete PredefinedType (#7006).
But if the type's own PredefinedType is edited to a concrete value
after occurrences are already assigned to it (e.g. via Bonsai's Edit
Type Attributes), edit_attributes() only kept the type's own
PredefinedType/ElementType consistent and never touched its
occurrences, leaving them with a stale explicit PredefinedType
(often NOTDEFINED, e.g. carried in from an import) alongside a
concretely typed type. This combination fails buildingSMART's OJT001
rule on export. Mirror assign_type()'s clearing so it also applies
when the type is edited, not just when it is assigned.

Generated with the assistance of an AI coding tool.

src/ifcopenshell-python/ifcopenshell/api/attribute/edit_attributes.py

@@ -38,6 +38,10 @@ def edit_attributes(file: ifcopenshell.file, product: ifcopenshell.entity_instan
     - PredefinedType to be "NOTDEFINED" if ElementType/ObjectType is None
     - PredefinedType to be "USERDEFINED" if ElementType/ObjectType is not None
 
+    If a type's own PredefinedType becomes a concrete value, its already
+    typed occurrences have their PredefinedType/ObjectType cleared to forbid
+    double typing (see #7006).
+
     :param product: The product you want to edit. This may be any rooted IFC
         entity.
     :param attributes: a dictionary of attribute names and values.
@@ -70,6 +74,19 @@ def edit_attributes(file: ifcopenshell.file, product: ifcopenshell.entity_instan
             elif element_type and predefined_type != "USERDEFINED":
                 product.PredefinedType = "USERDEFINED"
 
+            # Remove occurrences' PredefinedType / ObjectType to forbid double typing (see #7006)
+            type_predefined_type = ifcopenshell.util.element.get_predefined_type(product)
+            if type_predefined_type not in ("NOTDEFINED", None):
+                if hasattr(product, "ObjectTypeOf"):
+                    types_rel = next(iter(product.ObjectTypeOf), None)
+                else:
+                    types_rel = next(iter(getattr(product, "Types", ())), None)
+                if types_rel:
+                    for obj in types_rel.RelatedObjects:
+                        obj.ObjectType = None
+                        if hasattr(obj, "PredefinedType"):
+                            obj.PredefinedType = None
+
         elif (object_type := getattr_safe(product, "ObjectType")) is not ...:
             relating_type = ifcopenshell.util.element.get_type(product)
             # Allow for None due to https://github.com/buildingSMART/IFC4.3.x-development/issues/818