def visit_compare(self, node: nodes.Compare) -> None:
_operators = ["!=", "==", "is not", "is"]
# note: astroid.Compare has the left most operand in node.left
# while the rest are a list of tuples in node.ops
# the format of the tuple is ('compare operator sign', node)
# here we squash everything into `ops` to make it easier for processing later
ops = [("", node.left)]
ops.extend(node.ops)
iter_ops: Iterable[Any] = iter(ops)
ops = list(itertools.chain(*iter_ops))
for ops_idx in range(len(ops) - 2):
op_1 = ops[ops_idx]
op_2 = ops[ops_idx + 1]
op_3 = ops[ops_idx + 2]
error_detected = False
# x ?? ""
if utils.is_empty_str_literal(op_1) and op_2 in _operators:
error_detected = True
# '' ?? X
elif op_2 in _operators and utils.is_empty_str_literal(op_3):
error_detected = True
if error_detected:
self.add_message("compare-to-empty-string", node=node)
def test_is_empty_literal() -> None:
list_node = astroid.extract_node("a = []")
assert utils.is_base_container(list_node.value)
not_empty_list_node = astroid.extract_node("a = [1,2,3]")
assert not utils.is_base_container(not_empty_list_node.value)
tuple_node = astroid.extract_node("a = ()")
assert utils.is_base_container(tuple_node.value)
not_empty_tuple_node = astroid.extract_node("a = (1,2)")
assert not utils.is_base_container(not_empty_tuple_node.value)
dict_node = astroid.extract_node("a = {}")
assert utils.is_empty_dict_literal(dict_node.value)
not_empty_dict_node = astroid.extract_node("a = {1:1}")
assert not utils.is_empty_dict_literal(not_empty_dict_node.value)
string_node = astroid.extract_node("a = ''")
assert utils.is_empty_str_literal(string_node.value)
not_empty_string_node = astroid.extract_node("a = 'hello'")
assert not utils.is_empty_str_literal(not_empty_string_node.value)