def update_type(self, tpe, bases):
""" Change the bases of the given ``tpe``
"""
if not isinstance(tpe, PersistableType):
raise UnsupportedTypeError("Object is not a PersistableType")
if self.type_registry.is_static_type(tpe):
raise CannotUpdateType("Type '{}' is defined in code and cannot"
"be updated.".format(get_type_id(tpe)))
descriptor = self.type_registry.get_descriptor(tpe)
existing_attrs = dict_difference(descriptor.attributes,
descriptor.declared_attributes)
base_attrs = {}
for base in bases:
desc = self.type_registry.get_descriptor(base)
base_attrs.update(desc.attributes)
base_attrs = dict_difference(base_attrs,
descriptor.declared_attributes)
if existing_attrs != base_attrs:
raise CannotUpdateType("Inherited attributes are not identical")
match_clauses = [get_match_clause(tpe, 'type', self.type_registry)]
create_clauses = []
query_args = {}
for index, base in enumerate(bases):
name = 'base_{}'.format(index)
match = get_match_clause(base, name, self.type_registry)
create = "type -[:ISA {%s_props}]-> %s" % (name, name)
query_args["{}_props".format(name)] = {'base_index': index}
match_clauses.append(match)
create_clauses.append(create)
query = join_lines(
"MATCH",
(match_clauses, ','),
", type -[r:ISA]-> ()",
"DELETE r",
"CREATE",
(create_clauses, ','),
"RETURN type")
try:
next(self._execute(query, **query_args))
self.invalidate_type_system()
except StopIteration:
raise CannotUpdateType("Type or bases not found in the database.")
self.reload_types()