diff --git a/Lib/test/test_abc.py b/Lib/test/test_abc.py index 9f5afb241ae..000e5838e3c 100644 --- a/Lib/test/test_abc.py +++ b/Lib/test/test_abc.py @@ -149,6 +149,25 @@ def test_factory(abc_ABCMeta, abc_get_cache_token): self.assertEqual(D.foo(), 4) self.assertEqual(D().foo(), 4) + def test_object_new_with_one_abstractmethod(self): + class C(metaclass=abc_ABCMeta): + @abc.abstractmethod + def method_one(self): + pass + msg = r"class C with abstract method method_one" + self.assertRaisesRegex(TypeError, msg, C) + + def test_object_new_with_many_abstractmethods(self): + class C(metaclass=abc_ABCMeta): + @abc.abstractmethod + def method_one(self): + pass + @abc.abstractmethod + def method_two(self): + pass + msg = r"class C with abstract methods method_one, method_two" + self.assertRaisesRegex(TypeError, msg, C) + def test_abstractmethod_integration(self): for abstractthing in [abc.abstractmethod, abc.abstractproperty, abc.abstractclassmethod, diff --git a/Misc/NEWS.d/next/C API/2018-08-04-00-59-44.bpo-34331.iaUkmU.rst b/Misc/NEWS.d/next/C API/2018-08-04-00-59-44.bpo-34331.iaUkmU.rst new file mode 100644 index 00000000000..e45e0915dbf --- /dev/null +++ b/Misc/NEWS.d/next/C API/2018-08-04-00-59-44.bpo-34331.iaUkmU.rst @@ -0,0 +1,2 @@ +Use singular/plural noun in error message when instantiating an abstract +class with non-overriden abstract method(s). diff --git a/Objects/typeobject.c b/Objects/typeobject.c index 7575e5580bf..dfdac9e2e4f 100644 --- a/Objects/typeobject.c +++ b/Objects/typeobject.c @@ -3753,6 +3753,7 @@ object_new(PyTypeObject *type, PyObject *args, PyObject *kwds) PyObject *joined; PyObject *comma; _Py_static_string(comma_id, ", "); + Py_ssize_t method_count; /* Compute ", ".join(sorted(type.__abstractmethods__)) into joined. */ @@ -3773,14 +3774,18 @@ object_new(PyTypeObject *type, PyObject *args, PyObject *kwds) return NULL; } joined = PyUnicode_Join(comma, sorted_methods); + method_count = PyObject_Length(sorted_methods); Py_DECREF(sorted_methods); if (joined == NULL) return NULL; + if (method_count == -1) + return NULL; PyErr_Format(PyExc_TypeError, "Can't instantiate abstract class %s " - "with abstract methods %U", + "with abstract method%s %U", type->tp_name, + method_count > 1 ? "s" : "", joined); Py_DECREF(joined); return NULL;