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

Additional note: the `method_check_args` function in `Objects/descrobject.c` is written in such a way that it applies to all kinds of descriptors. In particular, a future re-implementation of `wrapper_descriptor` could use that code. CC @vstinner @encukou https://bugs.python.org/issue37645 Automerge-Triggered-By: @encukou
python · Nov 5, 2019 · bf17d41 · bf17d41
1 parent b396663
commit bf17d41
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Showing 11 changed files with 171 additions and 94 deletions.
diff --git a/Doc/c-api/object.rst b/Doc/c-api/object.rst
@@ -196,6 +196,7 @@ 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_Bytes(PyObject *o)
 
    .. index:: builtin: bytes

diff --git a/Include/cpython/object.h b/Include/cpython/object.h
@@ -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`.
  *

diff --git a/Lib/test/test_call.py b/Lib/test/test_call.py
@@ -74,7 +74,7 @@ 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):
@@ -90,19 +90,19 @@ def test_varargs7_kw(self):
         self.assertRaisesRegex(TypeError, msg, next, x=2)
 
     def test_varargs8_kw(self):
-        msg = r"^pack\(\) takes no keyword arguments$"
+        msg = r"^_struct[.]pack\(\) takes no keyword arguments$"
         self.assertRaisesRegex(TypeError, msg, struct.pack, x=2)
 
     def test_varargs9_kw(self):
-        msg = r"^pack_into\(\) takes no keyword arguments$"
+        msg = r"^_struct[.]pack_into\(\) takes no keyword arguments$"
         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):

diff --git a/Lib/test/test_descr.py b/Lib/test/test_descr.py
@@ -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 = "unbound method set.add() needs an argument"
 
         with self.assertRaises(TypeError) as cm:
             set_add()

diff --git a/Lib/test/test_extcall.py b/Lib/test/test_extcall.py
@@ -52,15 +52,15 @@
     >>> f(1, 2, **{'a': -1, 'b': 5}, **{'a': 4, 'c': 6})
     Traceback (most recent call last):
         ...
-    TypeError: f() got multiple values for keyword argument 'a'
+    TypeError: test.test_extcall.f() got multiple values for keyword argument 'a'
     >>> f(1, 2, **{'a': -1, 'b': 5}, a=4, c=6)
     Traceback (most recent call last):
         ...
-    TypeError: f() got multiple values for keyword argument 'a'
+    TypeError: test.test_extcall.f() got multiple values for keyword argument 'a'
     >>> f(1, 2, a=3, **{'a': 4}, **{'a': 5})
     Traceback (most recent call last):
         ...
-    TypeError: f() got multiple values for keyword argument 'a'
+    TypeError: test.test_extcall.f() got multiple values for keyword argument 'a'
     >>> f(1, 2, 3, *[4, 5], **{'a':6, 'b':7})
     (1, 2, 3, 4, 5) {'a': 6, 'b': 7}
     >>> f(1, 2, 3, x=4, y=5, *(6, 7), **{'a':8, 'b': 9})
@@ -118,7 +118,7 @@
     >>> g(*Nothing())
     Traceback (most recent call last):
       ...
-    TypeError: g() argument after * must be an iterable, not Nothing
+    TypeError: test.test_extcall.g() argument after * must be an iterable, not Nothing
 
     >>> class Nothing:
     ...     def __len__(self): return 5
@@ -127,7 +127,7 @@
     >>> g(*Nothing())
     Traceback (most recent call last):
       ...
-    TypeError: g() argument after * must be an iterable, not Nothing
+    TypeError: test.test_extcall.g() argument after * must be an iterable, not Nothing
 
     >>> class Nothing():
     ...     def __len__(self): return 5
@@ -247,17 +247,17 @@
     >>> h(*h)
     Traceback (most recent call last):
       ...
-    TypeError: h() argument after * must be an iterable, not function
+    TypeError: test.test_extcall.h() argument after * must be an iterable, not function
 
     >>> h(1, *h)
     Traceback (most recent call last):
       ...
-    TypeError: h() argument after * must be an iterable, not function
+    TypeError: test.test_extcall.h() argument after * must be an iterable, not function
 
     >>> h(*[1], *h)
     Traceback (most recent call last):
       ...
-    TypeError: h() argument after * must be an iterable, not function
+    TypeError: test.test_extcall.h() argument after * must be an iterable, not function
 
     >>> dir(*h)
     Traceback (most recent call last):
@@ -268,38 +268,38 @@
     >>> nothing(*h)
     Traceback (most recent call last):
       ...
-    TypeError: NoneType object argument after * must be an iterable, \
+    TypeError: None argument after * must be an iterable, \
 not function
 
     >>> h(**h)
     Traceback (most recent call last):
       ...
-    TypeError: h() argument after ** must be a mapping, not function
+    TypeError: test.test_extcall.h() argument after ** must be a mapping, not function
 
     >>> h(**[])
     Traceback (most recent call last):
       ...
-    TypeError: h() argument after ** must be a mapping, not list
+    TypeError: test.test_extcall.h() argument after ** must be a mapping, not list
 
     >>> h(a=1, **h)
     Traceback (most recent call last):
       ...
-    TypeError: h() argument after ** must be a mapping, not function
+    TypeError: test.test_extcall.h() argument after ** must be a mapping, not function
 
     >>> h(a=1, **[])
     Traceback (most recent call last):
       ...
-    TypeError: h() argument after ** must be a mapping, not list
+    TypeError: test.test_extcall.h() argument after ** must be a mapping, not list
 
     >>> h(**{'a': 1}, **h)
     Traceback (most recent call last):
       ...
-    TypeError: h() argument after ** must be a mapping, not function
+    TypeError: test.test_extcall.h() argument after ** must be a mapping, not function
 
     >>> h(**{'a': 1}, **[])
     Traceback (most recent call last):
       ...
-    TypeError: h() argument after ** must be a mapping, not list
+    TypeError: test.test_extcall.h() argument after ** must be a mapping, not list
 
     >>> dir(**h)
     Traceback (most recent call last):
@@ -309,7 +309,7 @@
     >>> nothing(**h)
     Traceback (most recent call last):
       ...
-    TypeError: NoneType object argument after ** must be a mapping, \
+    TypeError: None argument after ** must be a mapping, \
 not function
 
     >>> dir(b=1, **{'b': 1})
@@ -351,17 +351,17 @@
     >>> g(**MultiDict([('x', 1), ('x', 2)]))
     Traceback (most recent call last):
       ...
-    TypeError: g() got multiple values for keyword argument 'x'
+    TypeError: test.test_extcall.g() got multiple values for keyword argument 'x'
 
     >>> g(a=3, **MultiDict([('x', 1), ('x', 2)]))
     Traceback (most recent call last):
       ...
-    TypeError: g() got multiple values for keyword argument 'x'
+    TypeError: test.test_extcall.g() got multiple values for keyword argument 'x'
 
     >>> g(**MultiDict([('a', 3)]), **MultiDict([('x', 1), ('x', 2)]))
     Traceback (most recent call last):
       ...
-    TypeError: g() got multiple values for keyword argument 'x'
+    TypeError: test.test_extcall.g() got multiple values for keyword argument 'x'
 
 Another helper function
 

diff --git a/Lib/test/test_unpack_ex.py b/Lib/test/test_unpack_ex.py
@@ -236,27 +236,27 @@
     >>> f(x=5, **{'x': 3}, y=2)
     Traceback (most recent call last):
       ...
-    TypeError: f() got multiple values for keyword argument 'x'
+    TypeError: test.test_unpack_ex.f() got multiple values for keyword argument 'x'
 
     >>> f(**{'x': 3}, x=5, y=2)
     Traceback (most recent call last):
       ...
-    TypeError: f() got multiple values for keyword argument 'x'
+    TypeError: test.test_unpack_ex.f() got multiple values for keyword argument 'x'
 
     >>> f(**{'x': 3}, **{'x': 5}, y=2)
     Traceback (most recent call last):
       ...
-    TypeError: f() got multiple values for keyword argument 'x'
+    TypeError: test.test_unpack_ex.f() got multiple values for keyword argument 'x'
 
     >>> f(x=5, **{'x': 3}, **{'x': 2})
     Traceback (most recent call last):
       ...
-    TypeError: f() got multiple values for keyword argument 'x'
+    TypeError: test.test_unpack_ex.f() got multiple values for keyword argument 'x'
 
     >>> f(**{1: 3}, **{1: 5})
     Traceback (most recent call last):
       ...
-    TypeError: f() got multiple values for keyword argument '1'
+    TypeError: test.test_unpack_ex.f() got multiple values for keyword argument '1'
 
 Unpacking non-sequence
 

diff --git a/Misc/NEWS.d/next/C API/2019-07-21-21-08-47.bpo-37645.4DcUaI.rst b/Misc/NEWS.d/next/C API/2019-07-21-21-08-47.bpo-37645.4DcUaI.rst
@@ -0,0 +1,2 @@
+Add :c:func:`_PyObject_FunctionStr` to get a user-friendly string representation
+of a function-like object. Patch by Jeroen Demeyer.
diff --git a/Objects/descrobject.c b/Objects/descrobject.c
@@ -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,
+                         "unbound method %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(PyThreadState *tstate, PyObject *func)
 {
@@ -387,8 +380,12 @@ 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(tstate, func);
@@ -410,9 +407,13 @@ 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(tstate, func);

diff --git a/Objects/methodobject.c b/Objects/methodobject.c
@@ -334,29 +334,26 @@ _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(PyThreadState *tstate, PyObject *func, PyObject *kwnames)
 {
     assert(!_PyErr_Occurred(tstate));
     assert(PyCFunction_Check(func));
     if (kwnames && PyTuple_GET_SIZE(kwnames)) {
-        _PyErr_Format(tstate, PyExc_TypeError,
-                      "%.200s() takes no keyword arguments", get_name(func));
+        PyObject *funcstr = _PyObject_FunctionStr(func);
+        if (funcstr != NULL) {
+            _PyErr_Format(tstate, 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(PyThreadState *tstate, PyObject *func)
 {
@@ -412,9 +409,12 @@ cfunction_vectorcall_NOARGS(
     }
     Py_ssize_t nargs = PyVectorcall_NARGS(nargsf);
     if (nargs != 0) {
-        _PyErr_Format(tstate, PyExc_TypeError,
-                      "%.200s() takes no arguments (%zd given)",
-                      get_name(func), nargs);
+        PyObject *funcstr = _PyObject_FunctionStr(func);
+        if (funcstr != NULL) {
+            _PyErr_Format(tstate, PyExc_TypeError,
+                "%U takes no arguments (%zd given)", funcstr, nargs);
+            Py_DECREF(funcstr);
+        }
         return NULL;
     }
     PyCFunction meth = (PyCFunction)cfunction_enter_call(tstate, func);
@@ -436,9 +436,12 @@ cfunction_vectorcall_O(
     }
     Py_ssize_t nargs = PyVectorcall_NARGS(nargsf);
     if (nargs != 1) {
-        _PyErr_Format(tstate, PyExc_TypeError,
-                      "%.200s() takes exactly one argument (%zd given)",
-                      get_name(func), nargs);
+        PyObject *funcstr = _PyObject_FunctionStr(func);
+        if (funcstr != NULL) {
+            _PyErr_Format(tstate, PyExc_TypeError,
+                "%U takes exactly one argument (%zd given)", funcstr, nargs);
+            Py_DECREF(funcstr);
+        }
         return NULL;
     }
     PyCFunction meth = (PyCFunction)cfunction_enter_call(tstate, func);