bpo-32571: Avoid raising unneeded AttributeError and silencing it in C code (GH-5222)

Add two new private APIs: _PyObject_LookupAttr() and _PyObject_LookupAttrId()

1 files changed, 49 insertions, 27 deletions

diff --git a/Objects/object.c b/Objects/object.c
index 8cec6e2..7b2adbe 100644
--- a/Objects/object.c
+++ b/Objects/object.c
@@ -817,16 +817,11 @@ _PyObject_IsAbstract(PyObject *obj)
     if (obj == NULL)
         return 0;
 
-    isabstract = _PyObject_GetAttrId(obj, &PyId___isabstractmethod__);
-    if (isabstract == NULL) {
-        if (PyErr_ExceptionMatches(PyExc_AttributeError)) {
-            PyErr_Clear();
-            return 0;
-        }
-        return -1;
+    res = _PyObject_LookupAttrId(obj, &PyId___isabstractmethod__, &isabstract);
+    if (res > 0) {
+        res = PyObject_IsTrue(isabstract);
+        Py_DECREF(isabstract);
     }
-    res = PyObject_IsTrue(isabstract);
-    Py_DECREF(isabstract);
     return res;
 }
 
@@ -888,47 +883,74 @@ PyObject_GetAttr(PyObject *v, PyObject *name)
     return NULL;
 }
 
-PyObject *
-_PyObject_GetAttrWithoutError(PyObject *v, PyObject *name)
+int
+_PyObject_LookupAttr(PyObject *v, PyObject *name, PyObject **result)
 {
     PyTypeObject *tp = Py_TYPE(v);
-    PyObject *ret = NULL;
 
     if (!PyUnicode_Check(name)) {
         PyErr_Format(PyExc_TypeError,
                      "attribute name must be string, not '%.200s'",
                      name->ob_type->tp_name);
-        return NULL;
+        *result = NULL;
+        return -1;
     }
 
     if (tp->tp_getattro == PyObject_GenericGetAttr) {
-        return _PyObject_GenericGetAttrWithDict(v, name, NULL, 1);
+        *result = _PyObject_GenericGetAttrWithDict(v, name, NULL, 1);
+        if (*result != NULL) {
+            return 1;
+        }
+        if (PyErr_Occurred()) {
+            return -1;
+        }
+        return 0;
     }
     if (tp->tp_getattro != NULL) {
-        ret = (*tp->tp_getattro)(v, name);
+        *result = (*tp->tp_getattro)(v, name);
     }
     else if (tp->tp_getattr != NULL) {
         const char *name_str = PyUnicode_AsUTF8(name);
-        if (name_str == NULL)
-            return NULL;
-        ret = (*tp->tp_getattr)(v, (char *)name_str);
+        if (name_str == NULL) {
+            *result = NULL;
+            return -1;
+        }
+        *result = (*tp->tp_getattr)(v, (char *)name_str);
     }
-    if (ret == NULL && PyErr_ExceptionMatches(PyExc_AttributeError)) {
-        PyErr_Clear();
+    if (*result != NULL) {
+        return 1;
     }
-    return ret;
+    if (!PyErr_ExceptionMatches(PyExc_AttributeError)) {
+        return -1;
+    }
+    PyErr_Clear();
+    return 0;
+}
+
+int
+_PyObject_LookupAttrId(PyObject *v, _Py_Identifier *name, PyObject **result)
+{
+    PyObject *oname = _PyUnicode_FromId(name); /* borrowed */
+    if (!oname) {
+        *result = NULL;
+        return -1;
+    }
+    return  _PyObject_LookupAttr(v, oname, result);
 }
 
 int
 PyObject_HasAttr(PyObject *v, PyObject *name)
 {
-    PyObject *res = _PyObject_GetAttrWithoutError(v, name);
-    if (res != NULL) {
-        Py_DECREF(res);
-        return 1;
+    PyObject *res;
+    if (_PyObject_LookupAttr(v, name, &res) < 0) {
+        PyErr_Clear();
+        return 0;
     }
-    PyErr_Clear();
-    return 0;
+    if (res == NULL) {
+        return 0;
+    }
+    Py_DECREF(res);
+    return 1;
 }
 
 int