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Merged
JelleZijlstra merged 5 commits into from
Nov 5, 2022
Merged

gh-98284: better error message for undefined abstractmethod #97971

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c268395
[abc] better error message for undefined abstractmethod
kaushikcfd Oct 6, 2022
3603740
adds a NEWS entry
kaushikcfd Oct 9, 2022
4073b1f
corrects the NEWS entry
kaushikcfd Oct 15, 2022
6a762e4
Merge remote-tracking branch 'upstream/main' into abc_better_err_msg
kaushikcfd Oct 15, 2022
6ae052e
Avoid leaks by calling Py_DECREF in some code paths
kaushikcfd Nov 5, 2022
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1 change: 0 additions & 1 deletion Include/internal/pycore_global_strings.h
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Original file line numberDiff line numberDiff line change
Expand Up@@ -37,7 +37,6 @@ struct _Py_global_strings {
STRUCT_FOR_STR(anon_string, "<string>")
STRUCT_FOR_STR(anon_unknown, "<unknown>")
STRUCT_FOR_STR(close_br, "}")
STRUCT_FOR_STR(comma_sep, ", ")
STRUCT_FOR_STR(dbl_close_br, "}}")
STRUCT_FOR_STR(dbl_open_br, "{{")
STRUCT_FOR_STR(dbl_percent, "%%")
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5 changes: 0 additions & 5 deletions Include/internal/pycore_runtime_init_generated.h
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12 changes: 6 additions & 6 deletions Lib/test/test_abc.py
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Original file line numberDiff line numberDiff line change
Expand Up@@ -154,7 +154,7 @@ class C(metaclass=abc_ABCMeta):
@abc.abstractmethod
def method_one(self):
pass
msg = r"class C without an implementation for abstract method method_one"
msg = r"class C without an implementation for abstract method 'method_one'"
self.assertRaisesRegex(TypeError, msg, C)

def test_object_new_with_many_abstractmethods(self):
Expand All@@ -165,7 +165,7 @@ def method_one(self):
@abc.abstractmethod
def method_two(self):
pass
msg = r"class C without an implementation for abstract methods method_one, method_two"
msg = r"class C without an implementation for abstract methods 'method_one', 'method_two'"
self.assertRaisesRegex(TypeError, msg, C)

def test_abstractmethod_integration(self):
Expand DownExpand Up@@ -535,7 +535,7 @@ def updated_foo(self):
A.foo = updated_foo
abc.update_abstractmethods(A)
self.assertEqual(A.__abstractmethods__, {'foo', 'bar'})
msg = "class A without an implementation for abstract methods bar, foo"
msg = "class A without an implementation for abstract methods 'bar', 'foo'"
self.assertRaisesRegex(TypeError, msg, A)

def test_update_implementation(self):
Expand All@@ -547,7 +547,7 @@ def foo(self):
class B(A):
pass

msg = "class B without an implementation for abstract method foo"
msg = "class B without an implementation for abstract method 'foo'"
self.assertRaisesRegex(TypeError, msg, B)
self.assertEqual(B.__abstractmethods__, {'foo'})

Expand DownExpand Up@@ -605,7 +605,7 @@ def foo(self):

abc.update_abstractmethods(B)

msg = "class B without an implementation for abstract method foo"
msg = "class B without an implementation for abstract method 'foo'"
self.assertRaisesRegex(TypeError, msg, B)

def test_update_layered_implementation(self):
Expand All@@ -627,7 +627,7 @@ def foo(self):

abc.update_abstractmethods(C)

msg = "class C without an implementation for abstract method foo"
msg = "class C without an implementation for abstract method 'foo'"
self.assertRaisesRegex(TypeError, msg, C)

def test_update_multi_inheritance(self):
Expand Down
2 changes: 1 addition & 1 deletion Lib/test/test_dataclasses.py
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Expand Up@@ -3962,7 +3962,7 @@ class Date(A):
day: 'int'

self.assertTrue(inspect.isabstract(Date))
msg = 'class Date without an implementation for abstract method foo'
msg = "class Date without an implementation for abstract method 'foo'"
self.assertRaisesRegex(TypeError, msg, Date)


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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Library/2022-10-15-10-43-45.gh-issue-98284.SaVHTd.rst
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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,3 @@
Improved :class:`TypeError` message for undefined abstract methods of a
:class:`abc.ABC` instance. The names of the missing methods are surrounded
by single-quotes to highlight them.
19 changes: 13 additions & 6 deletions Objects/typeobject.c
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Original file line numberDiff line numberDiff line change
Expand Up@@ -4861,9 +4861,10 @@ object_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
PyObject *abstract_methods;
PyObject *sorted_methods;
PyObject *joined;
PyObject* comma_w_quotes_sep;
Py_ssize_t method_count;

/* Compute ", ".join(sorted(type.__abstractmethods__))
/* Compute "', '".join(sorted(type.__abstractmethods__))
into joined. */
abstract_methods = type_abstractmethods(type, NULL);
if (abstract_methods == NULL)
Expand All@@ -4876,22 +4877,28 @@ object_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
Py_DECREF(sorted_methods);
return NULL;
}
_Py_DECLARE_STR(comma_sep, ", ");
joined = PyUnicode_Join(&_Py_STR(comma_sep), sorted_methods);
comma_w_quotes_sep = PyUnicode_FromString("', '");
joined = PyUnicode_Join(comma_w_quotes_sep, sorted_methods);
method_count = PyObject_Length(sorted_methods);
Py_DECREF(sorted_methods);
if (joined == NULL)
if (joined == NULL) {
Py_DECREF(comma_w_quotes_sep);
return NULL;
if (method_count == -1)
}
if (method_count == -1) {
Py_DECREF(comma_w_quotes_sep);
Py_DECREF(joined);
return NULL;
}

PyErr_Format(PyExc_TypeError,
"Can't instantiate abstract class %s "
"without an implementation for abstract method%s %U",
"without an implementation for abstract method%s '%U'",
type->tp_name,
method_count > 1 ? "s" : "",
joined);
Py_DECREF(joined);
Py_DECREF(comma_w_quotes_sep);

@JelleZijlstraJelleZijlstraNov 5, 2022

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You also need to DECREF this in the two return NULL branches above.

Come to think of it, the second of those already leaks joined. It needs a Py_DECREF(joined).

@kaushikcfdkaushikcfdNov 5, 2022

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Aah, yep! Fixed in 6ae052e.

return NULL;
}
PyObject *obj = type->tp_alloc(type, 0);
Expand Down