8000 bpo-37645: add new function _PyObject_FunctionStr() by jdemeyer · Pull Request #14890 · python/cpython · GitHub
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Merged
merged 9 commits into from
Nov 5, 2019
Merged

bpo-37645: add new function _PyObject_FunctionStr() #14890

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2a55a9f
bpo-37645: add new function PyObject_FunctionStr()
jdemeyer Jul 21, 2019
733158d
bpo-37645: clear exception in check_args_iterable()
jdemeyer Jul 21, 2019
4c0c877
bpo-37645: rename PyObject_FunctionStr() -> _PyObject_FunctionStr()
jdemeyer Aug 4, 2019
2e1b44e
bpo-37645: use str(func) as fallback in _PyObject_FunctionStr()
jdemeyer Aug 18, 2019
fa20556
bpo-37645: review fixes
jdemeyer Sep 13, 2019
b2e56da
Handle error in PyObject_RichCompareBool
encukou Oct 22, 2019
21aee80
Add author to NEWS
encukou Oct 22, 2019
402ec96
Change format_kwargs_error to use _PyObject_FunctionStr as well
encukou Nov 5, 2019
0307ce9
Merge branch 'master' to resolve PyErr_Format/_PyErr_Format conflict
encukou Nov 5, 2019
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bpo-37645: add new function PyObject_FunctionStr()
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@jdemeyer < 8000 /div>
jdemeyer committed Aug 18, 2019
commit 2a55a9fdb9f7d637dae9781c4d8e7d65f1e75954
11 changes: 11 additions & 0 deletions Doc/c-api/object.rst
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Expand Up @@ -196,6 +196,17 @@ Object Protocol
This function now includes a debug assertion to help ensure that it
does not silently discard an active exception.


.. c:function:: PyObject* PyObject_FunctionStr(PyObject *func)

Return a user-friendly string representation of the function-like object
*func*. This returns ``func.__qualname__ + "()"`` if there is a
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Returning __qualname__ without module is not particularly useful.

If you want to return a full qualified name (long but unambiguous), return __module__ + '.' + __qualname__. __module__ can be omitted if it is 'builtins'.

If you want to return a short name (it is enough in many times), return __name__.

if __qualname__ is not available, you can use __name__ instead.

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if __qualname__ is not available, you can use __name__ instead.

This is mainly meant as replacement for PyEval_GetFuncName and all classes supported by that function implement __qualname__. So I see little reason for the additional complexity of supporting __name__.

``__qualname__`` attribute and ``type(func).__name__ + " object"``
otherwise. Note that there is no check that *func* is actually callable.
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Why not using the qualified name for type(func)?

Would it be possible to also add the module, except for builtin functions?

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Why not using the qualified name for type(func)?

I decided to use str(func) as fallback, which looks more useful than f"{type(func)} object".


.. versionadded:: 3.9


.. c:function:: PyObject* PyObject_Bytes(PyObject *o)

.. index:: builtin: bytes
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1 change: 1 addition & 0 deletions Include/cpython/object.h
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Expand Up @@ -348,6 +348,7 @@ static inline void _Py_Dealloc_inline(PyObject *op)
}
#define _Py_Dealloc(op) _Py_Dealloc_inline(op)

PyAPI_FUNC(PyObject *) PyObject_FunctionStr(PyObject *);

/* Safely decref `op` and set `op` to `op2`.
*
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6 changes: 3 additions & 3 deletions Lib/test/test_call.py
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Expand Up @@ -193,7 +193,7 @@ def test_varargs3_kw(self):
self.assertRaisesRegex(TypeError, msg, bool, x=2)

def test_varargs4_kw(self):
msg = r"^index\(\) takes no keyword arguments$"
msg = r"^list[.]index\(\) takes no keyword arguments$"
self.assertRaisesRegex(TypeError, msg, [].index, x=2)

def test_varargs5_kw(self):
Expand All @@ -217,11 +217,11 @@ def test_varargs9_kw(self):
self.assertRaisesRegex(TypeError, msg, struct.pack_into, x=2)

def test_varargs10_kw(self):
msg = r"^index\(\) takes no keyword arguments$"
msg = r"^deque[.]index\(\) takes no keyword arguments$"
self.assertRaisesRegex(TypeError, msg, collections.deque().index, x=2)

def test_varargs11_kw(self):
msg = r"^pack\(\) takes no keyword arguments$"
msg = r"^Struct[.]pack\(\) takes no keyword arguments$"
self.assertRaisesRegex(TypeError, msg, struct.Struct.pack, struct.Struct(""), x=2)

def test_varargs12_kw(self):
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2 changes: 1 addition & 1 deletion Lib/test/test_descr.py
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Expand Up @@ -1967,7 +1967,7 @@ def test_methods_in_c(self):
# different error messages.
set_add = set.add

expected_errmsg = "descriptor 'add' of 'set' object needs an argument"
expected_errmsg = "set.add() needs an argument"
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I consider this a regression: the message is now too similar to calling the method on an instance, but missing an argument.

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: set.add() takes exactly one argument (0 given)

>>> set.add()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: set.add() needs an argument

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Agree, this is confusing.

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I can change the error message to anything you like, except that it must contain the string set.add (the function name). So it could be

TypeError: unbound method set.add() needs an argument

or whatever (surely, this is better than anything mentioning descriptors).

Small rant: the bug is really this:

>>> set().add()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: add() takes exactly one argument (0 given)

For a Python method, it would correctly note that 2 arguments are required. This is difficult to fix in CPython since builtin_function_or_method doesn't really know whether it's a function or method. This was one of the things that the rejected PEP 580 would have addressed.


with self.assertRaises(TypeError) as cm:
set_add()
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/C API/2019-07-21-21-08-47.bpo-37645.4DcUaI.rst
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@@ -0,0 +1,2 @@
Add :c:func:`PyObject_FunctionStr` to get a user-friendly string representation
of a function-like object.
57 changes: 29 additions & 28 deletions Objects/descrobject.c
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Expand Up @@ -231,45 +231,38 @@ getset_set(PyGetSetDescrObject *descr, PyObject *obj, PyObject *value)
*
* First, common helpers
*/
static const char *
get_name(PyObject *func) {
assert(PyObject_TypeCheck(func, &PyMethodDescr_Type));
return ((PyMethodDescrObject *)func)->d_method->ml_name;
}

typedef void (*funcptr)(void);

static inline int
method_check_args(PyObject *func, PyObject *const *args, Py_ssize_t nargs, PyObject *kwnames)
{
assert(!PyErr_Occurred());
assert(PyObject_TypeCheck(func, &PyMethodDescr_Type));
if (nargs < 1) {
PyErr_Format(PyExc_TypeError,
"descriptor '%.200s' of '%.100s' "
"object needs an argument",
get_name(func), PyDescr_TYPE(func)->tp_name);
PyObject *funcstr = PyObject_FunctionStr(func);
if (funcstr != NULL) {
PyErr_Format(PyExc_TypeError,
"%U needs an argument", funcstr);
Py_DECREF(funcstr);
}
return -1;
}
PyObject *self = args[0];
if (!_PyObject_RealIsSubclass((PyObject *)Py_TYPE(self),
(PyObject *)PyDescr_TYPE(func)))
{
PyErr_Format(PyExc_TypeError,
"descriptor '%.200s' for '%.100s' objects "
"doesn't apply to a '%.100s' object",
get_name(func), PyDescr_TYPE(func)->tp_name,
Py_TYPE(self)->tp_name);
PyObject *dummy;
if (descr_check((PyDescrObject *)func, self, &dummy)) {
return -1;
}
if (kwnames && PyTuple_GET_SIZE(kwnames)) {
PyErr_Format(PyExc_TypeError,
"%.200s() takes no keyword arguments", get_name(func));
PyObject *funcstr = PyObject_FunctionStr(func);
if (funcstr != NULL) {
PyErr_Format(PyExc_TypeError,
"%U takes no keyword arguments", funcstr);
Py_DECREF(funcstr);
}
return -1;
}
return 0;
}

typedef void (*funcptr)(void);

static inline funcptr
method_enter_call(PyObject *func)
{
Expand Down Expand Up @@ -382,8 +375,12 @@ method_vectorcall_NOARGS(
return NULL;
}
if (nargs != 1) {
PyErr_Format(PyExc_TypeError,
"%.200s() takes no arguments (%zd given)", get_name(func), nargs-1);
PyObject *funcstr = PyObject_FunctionStr(func);
if (funcstr != NULL) {
PyErr_Format(PyExc_TypeError,
"%U takes no arguments (%zd given)", funcstr, nargs-1);
Py_DECREF(funcstr);
}
return NULL;
}
PyCFunction meth = (PyCFunction)method_enter_call(func);
Expand All @@ -404,9 +401,13 @@ method_vectorcall_O(
return NULL;
}
if (nargs != 2) {
PyErr_Format(PyExc_TypeError,
"%.200s() takes exactly one argument (%zd given)",
get_name(func), nargs-1);
PyObject *funcstr = PyObject_FunctionStr(func);
if (funcstr != NULL) {
PyErr_Format(PyExc_TypeError,
"%U takes exactly one argument (%zd given)",
funcstr, nargs-1);
Py_DECREF(funcstr);
}
return NULL;
}
PyCFunction meth = (PyCFunction)method_enter_call(func);
Expand Down
36 changes: 20 additions & 16 deletions Objects/methodobject.c
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Expand Up @@ -331,29 +331,26 @@ PyCFunction_Fini(void)
*
* First, common helpers
*/
static const char *
get_name(PyObject *func)
{
assert(PyCFunction_Check(func));
PyMethodDef *method = ((PyCFunctionObject *)func)->m_ml;
return method->ml_name;
}

typedef void (*funcptr)(void);

static inline int
cfunction_check_kwargs(PyObject *func, PyObject *kwnames)
{
assert(!PyErr_Occurred());
assert(PyCFunction_Check(func));
if (kwnames && PyTuple_GET_SIZE(kwnames)) {
PyErr_Format(PyExc_TypeError,
"%.200s() takes no keyword arguments", get_name(func));
PyObject *funcstr = PyObject_FunctionStr(func);
if (funcstr != NULL) {
PyErr_Format(PyExc_TypeError,
"%U takes no keyword arguments", funcstr);
Py_DECREF(funcstr);
}
return -1;
}
return 0;
}

typedef void (*funcptr)(void);

static inline funcptr
cfunction_enter_call(PyObject *func)
{
Expand Down Expand Up @@ -406,8 +403,12 @@ cfunction_vectorcall_NOARGS(
}
Py_ssize_t nargs = PyVectorcall_NARGS(nargsf);
if (nargs != 0) {
PyErr_Format(PyExc_TypeError,
"%.200s() takes no arguments (%zd given)", get_name(func), nargs);
PyObject *funcstr = PyObject_FunctionStr(func);
if (funcstr != NULL) {
PyErr_Format(PyExc_TypeError,
"%U takes no arguments (%zd given)", funcstr, nargs);
Py_DECREF(funcstr);
}
return NULL;
}
PyCFunction meth = (PyCFunction)cfunction_enter_call(func);
Expand All @@ -428,9 +429,12 @@ cfunction_vectorcall_O(
}
Py_ssize_t nargs = PyVectorcall_NARGS(nargsf);
if (nargs != 1) {
PyErr_Format(PyExc_TypeError,
"%.200s() takes exactly one argument (%zd given)",
get_name(func), nargs);
PyObject *funcstr = PyObject_FunctionStr(func);
if (funcstr != NULL) {
PyErr_Format(PyExc_TypeError,
"%U takes exactly one argument (%zd given)", funcstr, nargs);
Py_DECREF(funcstr);
}
return NULL;
}
PyCFunction meth = (PyCFunction)cfunction_enter_call(func);
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28 changes: 28 additions & 0 deletions Objects/object.c
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Expand Up @@ -663,6 +663,34 @@ PyObject_Bytes(PyObject *v)
return PyBytes_FromObject(v);
}


/*
def PyObject_FunctionStr(f):
try:
return f.__qualname__ + "()"
except Exception:
return type(f).__name__ + " object"
*/
PyObject *
PyObject_FunctionStr(PyObject *f)
{
_Py_IDENTIFIER(__qualname__);
PyObject *name = _PyObject_GetAttrId(f, &PyId___qualname__);
if (name != NULL) {
PyObject *res = PyUnicode_FromFormat("%S()", name);
Py_DECREF(name);
return res;
}
/* __qualname__ lookup failed */
if (!PyErr_ExceptionMatches(PyExc_Exception)) {
/* An exception not inheriting from Exception, like KeyboardInterrupt.
* Propagate it. */
return NULL;
}
PyErr_Clear();
return PyUnicode_FromFormat("%.200s object", Py_TYPE(f)->tp_name);
}

/* For Python 3.0.1 and later, the old three-way comparison has been
completely removed in favour of rich comparisons. PyObject_Compare() and
PyObject_Cmp() are gone, and the builtin cmp function no longer exists.
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13 changes: 7 additions & 6 deletions Python/ceval.c
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Expand Up @@ -5341,12 +5341,13 @@ static int
check_args_iterable(PyThreadState *tstate, PyObject *func, PyObject *args)
{
if (args->ob_type->tp_iter == NULL && !PySequence_Check(args)) {
_PyErr_Format(tstate, PyExc_TypeError,
"%.200s%.200s argument after * "
"must be an iterable, not %.200s",
PyEval_GetFuncName(func),
PyEval_GetFuncDesc(func),
args->ob_type->tp_name);
PyObject *funcstr = PyObject_FunctionStr(func);
if (funcstr != NULL) {
_PyErr_Format(tstate, PyExc_TypeError,
"%U argument after * must be an iterable, not %.200s",
funcstr, Py_TYPE(args)->tp_name);
Py_DECREF(funcstr);
}
return -1;
}
return 0;
Expand Down
0