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

3 files changed, 107 insertions, 45 deletions

diff --git a/Objects/descrobject.c b/Objects/descrobject.c
index dbab4cd..342b993 100644
--- 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
index c780904..8f752c6 100644
--- a/Objects/methodobject.c
+++ b/Objects/methodobject.c
@@ -334,15 +334,6 @@ _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)
@@ -350,13 +341,19 @@ 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);
diff --git a/Objects/object.c b/Objects/object.c
index 9536d46..3e61282 100644
--- a/Objects/object.c
+++ b/Objects/object.c
@@ -681,6 +681,64 @@ PyObject_Bytes(PyObject *v)
     return PyBytes_FromObject(v);
 }
 
+
+/*
+def _PyObject_FunctionStr(x):
+    try:
+        qualname = x.__qualname__
+    except AttributeError:
+        return str(x)
+    try:
+        mod = x.__module__
+        if mod is not None and mod != 'builtins':
+            return f"{x.__module__}.{qualname}()"
+    except AttributeError:
+        pass
+    return qualname
+*/
+PyObject *
+_PyObject_FunctionStr(PyObject *x)
+{
+    _Py_IDENTIFIER(__module__);
+    _Py_IDENTIFIER(__qualname__);
+    _Py_IDENTIFIER(builtins);
+    assert(!PyErr_Occurred());
+    PyObject *qualname;
+    int ret = _PyObject_LookupAttrId(x, &PyId___qualname__, &qualname);
+    if (qualname == NULL) {
+        if (ret < 0) {
+            return NULL;
+        }
+        return PyObject_Str(x);
+    }
+    PyObject *module;
+    PyObject *result = NULL;
+    ret = _PyObject_LookupAttrId(x, &PyId___module__, &module);
+    if (module != NULL && module != Py_None) {
+        PyObject *builtinsname = _PyUnicode_FromId(&PyId_builtins);
+        if (builtinsname == NULL) {
+            goto done;
+        }
+        ret = PyObject_RichCompareBool(module, builtinsname, Py_NE);
+        if (ret < 0) {
+            // error
+            goto done;
+        }
+        if (ret > 0) {
+            result = PyUnicode_FromFormat("%S.%S()", module, qualname);
+            goto done;
+        }
+    }
+    else if (ret < 0) {
+        goto done;
+    }
+    result = PyUnicode_FromFormat("%S()", qualname);
+done:
+    Py_DECREF(qualname);
+    Py_XDECREF(module);
+    return result;
+}
+
 /* 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.