pythongh-106521: Add PyObject_GetOptionalAttr() function

It is a new name of former _PyObject_LookupAttr().
serhiy-storchaka · Jul 7, 2023 · cf4d3cd · cf4d3cd
1 parent 363f4f9
commit cf4d3cd
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diff --git a/Doc/c-api/object.rst b/Doc/c-api/object.rst
@@ -37,7 +37,8 @@ Object Protocol
 
       Exceptions that occur when this calls :meth:`~object.__getattr__` and
       :meth:`~object.__getattribute__` methods are silently ignored.
-      For proper error handling, use :c:func:`PyObject_GetAttr` instead.
+      For proper error handling, use :c:func:`PyObject_GetOptionalAttr` or
+      :c:func:`PyObject_GetAttr` instead.
 
 
 .. c:function:: int PyObject_HasAttrString(PyObject *o, const char *attr_name)
@@ -60,6 +61,22 @@ Object Protocol
    value on success, or ``NULL`` on failure.  This is the equivalent of the Python
    expression ``o.attr_name``.
 
+   If the missing attribute should not be treated as a failure, you can use
+   :c:func:`PyObject_GetOptionalAttr` instead.
+
+
+.. c:function:: int PyObject_GetOptionalAttr(PyObject *obj, PyObject *attr_name, PyObject **result);
+
+   Replacement of :c:func:`PyObject_GetAttr` which doesn't raise
+   :exc:`AttributeError`.
+
+   Return ``1`` and set ``*result != NULL`` if an attribute is found.
+   Return ``0`` and set ``*result == NULL`` if an attribute is not found;
+   an :exc:`AttributeError` is silenced.
+   Return ``-1`` and set ``*result == NULL`` if an error other than
+   :exc:`AttributeError` is raised.
+
+   .. versionadded:: 3.13
 
 .. c:function:: PyObject* PyObject_GetAttrString(PyObject *o, const char *attr_name)
 

diff --git a/Doc/whatsnew/3.13.rst b/Doc/whatsnew/3.13.rst
@@ -441,6 +441,12 @@ New Features
   ``NULL`` if the referent is no longer live.
   (Contributed by Victor Stinner in :gh:`105927`.)
 
+* Add :c:func:`PyObject_GetOptionalAttr` function: replacement of
+  :c:func:`PyObject_GetAttr` which doesn't raise :exc:`AttributeError`.
+  It is convenient and faster if the missing attribute should not be treated
+  as a failure.
+  (Contributed by Serhiy Storchaka in :gh:`106521`.)
+
 * If Python is built in :ref:`debug mode <debug-build>` or :option:`with
   assertions <--with-assertions>`, :c:func:`PyTuple_SET_ITEM` and
   :c:func:`PyList_SET_ITEM` now check the index argument with an assertion.

diff --git a/Include/abstract.h b/Include/abstract.h
@@ -60,6 +60,20 @@ extern "C" {
    This is the equivalent of the Python expression: o.attr_name. */
 
 
+/* Implemented elsewhere:
+
+   int PyObject_GetOptionalAttr(PyObject *obj, PyObject *attr_name, PyObject **result);
+
+   Replacement of PyObject_GetAttr() which doesn't raise AttributeError.
+
+   Return 1 and set *result != NULL if an attribute is found.
+   Return 0 and set *result == NULL if an attribute is not found;
+   an AttributeError is silenced.
+   Return -1 and set *result == NULL if an error other than AttributeError
+   is raised.
+*/
+
+
 /* Implemented elsewhere:
 
    int PyObject_SetAttrString(PyObject *o, const char *attr_name, PyObject *v);

diff --git a/Include/cpython/object.h b/Include/cpython/object.h
@@ -293,17 +293,6 @@ PyAPI_FUNC(int) _PyObject_IsFreed(PyObject *);
 PyAPI_FUNC(int) _PyObject_IsAbstract(PyObject *);
 PyAPI_FUNC(PyObject *) _PyObject_GetAttrId(PyObject *, _Py_Identifier *);
 PyAPI_FUNC(int) _PyObject_SetAttrId(PyObject *, _Py_Identifier *, PyObject *);
-/* Replacements of PyObject_GetAttr() and _PyObject_GetAttrId() which
-   don't raise AttributeError.
-
-   Return 1 and set *result != NULL if an attribute is found.
-   Return 0 and set *result == NULL if an attribute is not found;
-   an AttributeError is silenced.
-   Return -1 and set *result == NULL if an error other than AttributeError
-   is raised.
-*/
-PyAPI_FUNC(int) _PyObject_LookupAttr(PyObject *, PyObject *, PyObject **);
-PyAPI_FUNC(int) _PyObject_LookupAttrId(PyObject *, _Py_Identifier *, PyObject **);
 
 PyAPI_FUNC(int) _PyObject_GetMethod(PyObject *obj, PyObject *name, PyObject **method);
 

diff --git a/Include/object.h b/Include/object.h
@@ -393,6 +393,9 @@ PyAPI_FUNC(PyObject *) PyObject_GetAttrString(PyObject *, const char *);
 PyAPI_FUNC(int) PyObject_SetAttrString(PyObject *, const char *, PyObject *);
 PyAPI_FUNC(int) PyObject_HasAttrString(PyObject *, const char *);
 PyAPI_FUNC(PyObject *) PyObject_GetAttr(PyObject *, PyObject *);
+#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x030d0000
+PyAPI_FUNC(int) PyObject_GetOptionalAttr(PyObject *, PyObject *, PyObject **);
+#endif
 PyAPI_FUNC(int) PyObject_SetAttr(PyObject *, PyObject *, PyObject *);
 PyAPI_FUNC(int) PyObject_HasAttr(PyObject *, PyObject *);
 PyAPI_FUNC(PyObject *) PyObject_SelfIter(PyObject *);

diff --git a/Misc/NEWS.d/next/C API/2023-07-07-19-14-00.gh-issue-106521.Veh9f3.rst b/Misc/NEWS.d/next/C API/2023-07-07-19-14-00.gh-issue-106521.Veh9f3.rst
@@ -0,0 +1 @@
+Add :c:func:`PyObject_GetOptionalAttr` function.
diff --git a/Modules/_abc.c b/Modules/_abc.c
@@ -361,7 +361,7 @@ compute_abstract_methods(PyObject *self)
         PyObject *item = PyTuple_GET_ITEM(bases, pos);  // borrowed
         PyObject *base_abstracts, *iter;
 
-        if (_PyObject_LookupAttr(item, &_Py_ID(__abstractmethods__),
+        if (PyObject_GetOptionalAttr(item, &_Py_ID(__abstractmethods__),
                                  &base_abstracts) < 0) {
             goto error;
         }
@@ -375,7 +375,7 @@ compute_abstract_methods(PyObject *self)
         Py_DECREF(base_abstracts);
         PyObject *key, *value;
         while ((key = PyIter_Next(iter))) {
-            if (_PyObject_LookupAttr(self, key, &value) < 0) {
+            if (PyObject_GetOptionalAttr(self, key, &value) < 0) {
                 Py_DECREF(key);
                 Py_DECREF(iter);
                 goto error;

diff --git a/Modules/_asynciomodule.c b/Modules/_asynciomodule.c
@@ -249,7 +249,7 @@ get_future_loop(asyncio_state *state, PyObject *fut)
         return Py_NewRef(loop);
     }
 
-    if (_PyObject_LookupAttr(fut, &_Py_ID(get_loop), &getloop) < 0) {
+    if (PyObject_GetOptionalAttr(fut, &_Py_ID(get_loop), &getloop) < 0) {
         return NULL;
     }
     if (getloop != NULL) {
@@ -2981,7 +2981,7 @@ task_step_handle_result_impl(asyncio_state *state, TaskObj *task, PyObject *resu
     }
 
     /* Check if `result` is a Future-compatible object */
-    if (_PyObject_LookupAttr(result, &_Py_ID(_asyncio_future_blocking), &o) < 0) {
+    if (PyObject_GetOptionalAttr(result, &_Py_ID(_asyncio_future_blocking), &o) < 0) {
         goto fail;
     }
     if (o != NULL && o != Py_None) {

diff --git a/Modules/_csv.c b/Modules/_csv.c
@@ -1450,7 +1450,7 @@ csv_writer(PyObject *module, PyObject *args, PyObject *keyword_args)
         Py_DECREF(self);
         return NULL;
     }
-    if (_PyObject_LookupAttr(output_file,
+    if (PyObject_GetOptionalAttr(output_file,
                              module_state->str_write,
                              &self->write) < 0) {
         Py_DECREF(self);

diff --git a/Modules/_ctypes/_ctypes.c b/Modules/_ctypes/_ctypes.c
@@ -851,7 +851,7 @@ CDataType_from_param(PyObject *type, PyObject *value)
         return NULL;
     }
 
-    if (_PyObject_LookupAttr(value, &_Py_ID(_as_parameter_), &as_parameter) < 0) {
+    if (PyObject_GetOptionalAttr(value, &_Py_ID(_as_parameter_), &as_parameter) < 0) {
         return NULL;
     }
     if (as_parameter) {
@@ -1495,7 +1495,7 @@ PyCArrayType_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
     stgdict = NULL;
     type_attr = NULL;
 
-    if (_PyObject_LookupAttr((PyObject *)result, &_Py_ID(_length_), &length_attr) < 0) {
+    if (PyObject_GetOptionalAttr((PyObject *)result, &_Py_ID(_length_), &length_attr) < 0) {
         goto error;
     }
     if (!length_attr) {
@@ -1528,7 +1528,7 @@ PyCArrayType_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
         goto error;
     }
 
-    if (_PyObject_LookupAttr((PyObject *)result, &_Py_ID(_type_), &type_attr) < 0) {
+    if (PyObject_GetOptionalAttr((PyObject *)result, &_Py_ID(_type_), &type_attr) < 0) {
         goto error;
     }
     if (!type_attr) {
@@ -1720,7 +1720,7 @@ c_wchar_p_from_param(PyObject *type, PyObject *value)
         }
     }
 
-    if (_PyObject_LookupAttr(value, &_Py_ID(_as_parameter_), &as_parameter) < 0) {
+    if (PyObject_GetOptionalAttr(value, &_Py_ID(_as_parameter_), &as_parameter) < 0) {
         return NULL;
     }
     if (as_parameter) {
@@ -1784,7 +1784,7 @@ c_char_p_from_param(PyObject *type, PyObject *value)
         }
     }
 
-    if (_PyObject_LookupAttr(value, &_Py_ID(_as_parameter_), &as_parameter) < 0) {
+    if (PyObject_GetOptionalAttr(value, &_Py_ID(_as_parameter_), &as_parameter) < 0) {
         return NULL;
     }
     if (as_parameter) {
@@ -1919,7 +1919,7 @@ c_void_p_from_param(PyObject *type, PyObject *value)
         }
     }
 
-    if (_PyObject_LookupAttr(value, &_Py_ID(_as_parameter_), &as_parameter) < 0) {
+    if (PyObject_GetOptionalAttr(value, &_Py_ID(_as_parameter_), &as_parameter) < 0) {
         return NULL;
     }
     if (as_parameter) {
@@ -2054,7 +2054,7 @@ PyCSimpleType_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
     if (result == NULL)
         return NULL;
 
-    if (_PyObject_LookupAttr((PyObject *)result, &_Py_ID(_type_), &proto) < 0) {
+    if (PyObject_GetOptionalAttr((PyObject *)result, &_Py_ID(_type_), &proto) < 0) {
         return NULL;
     }
     if (!proto) {
@@ -2266,7 +2266,7 @@ PyCSimpleType_from_param(PyObject *type, PyObject *value)
     PyObject *exc = PyErr_GetRaisedException();
     Py_DECREF(parg);
 
-    if (_PyObject_LookupAttr(value, &_Py_ID(_as_parameter_), &as_parameter) < 0) {
+    if (PyObject_GetOptionalAttr(value, &_Py_ID(_as_parameter_), &as_parameter) < 0) {
         Py_XDECREF(exc);
         return NULL;
     }
@@ -2429,7 +2429,7 @@ converters_from_argtypes(PyObject *ob)
         }
  */
 
-        if (_PyObject_LookupAttr(tp, &_Py_ID(from_param), &cnv) <= 0) {
+        if (PyObject_GetOptionalAttr(tp, &_Py_ID(from_param), &cnv) <= 0) {
             Py_DECREF(converters);
             Py_DECREF(ob);
             if (!PyErr_Occurred()) {
@@ -2489,7 +2489,7 @@ make_funcptrtype_dict(StgDictObject *stgdict)
             return -1;
         }
         stgdict->restype = Py_NewRef(ob);
-        if (_PyObject_LookupAttr(ob, &_Py_ID(_check_retval_),
+        if (PyObject_GetOptionalAttr(ob, &_Py_ID(_check_retval_),
                                    &stgdict->checker) < 0)
         {
             return -1;
@@ -3275,7 +3275,7 @@ PyCFuncPtr_set_restype(PyCFuncPtrObject *self, PyObject *ob, void *Py_UNUSED(ign
                         "restype must be a type, a callable, or None");
         return -1;
     }
-    if (_PyObject_LookupAttr(ob, &_Py_ID(_check_retval_), &checker) < 0) {
+    if (PyObject_GetOptionalAttr(ob, &_Py_ID(_check_retval_), &checker) < 0) {
         return -1;
     }
     oldchecker = self->checker;

diff --git a/Modules/_ctypes/callproc.c b/Modules/_ctypes/callproc.c
@@ -727,7 +727,7 @@ static int ConvParam(PyObject *obj, Py_ssize_t index, struct argument *pa)
 
     {
         PyObject *arg;
-        if (_PyObject_LookupAttr(obj, &_Py_ID(_as_parameter_), &arg) < 0) {
+        if (PyObject_GetOptionalAttr(obj, &_Py_ID(_as_parameter_), &arg) < 0) {
             return -1;
         }
         /* Which types should we exactly allow here?

diff --git a/Modules/_ctypes/stgdict.c b/Modules/_ctypes/stgdict.c
@@ -295,7 +295,7 @@ MakeAnonFields(PyObject *type)
     PyObject *anon_names;
     Py_ssize_t i;
 
-    if (_PyObject_LookupAttr(type, &_Py_ID(_anonymous_), &anon) < 0) {
+    if (PyObject_GetOptionalAttr(type, &_Py_ID(_anonymous_), &anon) < 0) {
         return -1;
     }
     if (anon == NULL) {
@@ -385,7 +385,7 @@ PyCStructUnionType_update_stgdict(PyObject *type, PyObject *fields, int isStruct
     if (fields == NULL)
         return 0;
 
-    if (_PyObject_LookupAttr(type, &_Py_ID(_swappedbytes_), &tmp) < 0) {
+    if (PyObject_GetOptionalAttr(type, &_Py_ID(_swappedbytes_), &tmp) < 0) {
         return -1;
     }
     if (tmp) {
@@ -396,7 +396,7 @@ PyCStructUnionType_update_stgdict(PyObject *type, PyObject *fields, int isStruct
         big_endian = PY_BIG_ENDIAN;
     }
 
-    if (_PyObject_LookupAttr(type, &_Py_ID(_pack_), &tmp) < 0) {
+    if (PyObject_GetOptionalAttr(type, &_Py_ID(_pack_), &tmp) < 0) {
         return -1;
     }
     if (tmp) {

diff --git a/Modules/_datetimemodule.c b/Modules/_datetimemodule.c
@@ -3791,7 +3791,7 @@ tzinfo_reduce(PyObject *self, PyObject *Py_UNUSED(ignored))
     PyObject *args, *state;
     PyObject *getinitargs;
 
-    if (_PyObject_LookupAttr(self, &_Py_ID(__getinitargs__), &getinitargs) < 0) {
+    if (PyObject_GetOptionalAttr(self, &_Py_ID(__getinitargs__), &getinitargs) < 0) {
         return NULL;
     }
     if (getinitargs != NULL) {

diff --git a/Modules/_elementtree.c b/Modules/_elementtree.c
@@ -3530,7 +3530,7 @@ expat_start_doctype_handler(XMLParserObject *self,
                                            sysid_obj, NULL);
         Py_XDECREF(res);
     }
-    else if (_PyObject_LookupAttr((PyObject *)self, st->str_doctype, &res) > 0) {
+    else if (PyObject_GetOptionalAttr((PyObject *)self, st->str_doctype, &res) > 0) {
         (void)PyErr_WarnEx(PyExc_RuntimeWarning,
                 "The doctype() method of XMLParser is ignored.  "
                 "Define doctype() method on the TreeBuilder target.",

diff --git a/Modules/_io/bufferedio.c b/Modules/_io/bufferedio.c
@@ -1463,7 +1463,7 @@ buffered_repr(buffered *self)
 {
     PyObject *nameobj, *res;
 
-    if (_PyObject_LookupAttr((PyObject *) self, &_Py_ID(name), &nameobj) < 0) {
+    if (PyObject_GetOptionalAttr((PyObject *) self, &_Py_ID(name), &nameobj) < 0) {
         if (!PyErr_ExceptionMatches(PyExc_ValueError)) {
             return NULL;
         }
@@ -1630,7 +1630,7 @@ _bufferedreader_read_all(buffered *self)
     }
     _bufferedreader_reset_buf(self);
 
-    if (_PyObject_LookupAttr(self->raw, &_Py_ID(readall), &readall) < 0) {
+    if (PyObject_GetOptionalAttr(self->raw, &_Py_ID(readall), &readall) < 0) {
         goto cleanup;
     }
     if (readall) {

diff --git a/Modules/_io/fileio.c b/Modules/_io/fileio.c
@@ -1099,7 +1099,7 @@ fileio_repr(fileio *self)
     if (self->fd < 0)
         return PyUnicode_FromFormat("<_io.FileIO [closed]>");
 
-    if (_PyObject_LookupAttr((PyObject *) self, &_Py_ID(name), &nameobj) < 0) {
+    if (PyObject_GetOptionalAttr((PyObject *) self, &_Py_ID(name), &nameobj) < 0) {
         return NULL;
     }
     if (nameobj == NULL) {

diff --git a/Modules/_io/iobase.c b/Modules/_io/iobase.c
@@ -148,7 +148,7 @@ iobase_is_closed(PyObject *self)
     int ret;
     /* This gets the derived attribute, which is *not* __IOBase_closed
        in most cases! */
-    ret = _PyObject_LookupAttr(self, &_Py_ID(__IOBase_closed), &res);
+    ret = PyObject_GetOptionalAttr(self, &_Py_ID(__IOBase_closed), &res);
     Py_XDECREF(res);
     return ret;
 }
@@ -196,7 +196,7 @@ iobase_check_closed(PyObject *self)
     int closed;
     /* This gets the derived attribute, which is *not* __IOBase_closed
        in most cases! */
-    closed = _PyObject_LookupAttr(self, &_Py_ID(closed), &res);
+    closed = PyObject_GetOptionalAttr(self, &_Py_ID(closed), &res);
     if (closed > 0) {
         closed = PyObject_IsTrue(res);
         Py_DECREF(res);
@@ -303,7 +303,7 @@ iobase_finalize(PyObject *self)
 
     /* If `closed` doesn't exist or can't be evaluated as bool, then the
        object is probably in an unusable state, so ignore. */
-    if (_PyObject_LookupAttr(self, &_Py_ID(closed), &res) <= 0) {
+    if (PyObject_GetOptionalAttr(self, &_Py_ID(closed), &res) <= 0) {
         PyErr_Clear();
         closed = -1;
     }
@@ -571,7 +571,7 @@ _io__IOBase_readline_impl(PyObject *self, Py_ssize_t limit)
     PyObject *peek, *buffer, *result;
     Py_ssize_t old_size = -1;
 
-    if (_PyObject_LookupAttr(self, &_Py_ID(peek), &peek) < 0) {
+    if (PyObject_GetOptionalAttr(self, &_Py_ID(peek), &peek) < 0) {
         return NULL;
     }