pythongh-92216: improve performance of hasattr for type objects (pythonGH-99979)

Author: eendebakpt

Include/internal/pycore_typeobject.h

@@ -74,6 +74,10 @@ extern static_builtin_state * _PyStaticType_GetState(PyTypeObject *);
 extern void _PyStaticType_ClearWeakRefs(PyTypeObject *type);
 extern void _PyStaticType_Dealloc(PyTypeObject *type);
 
+PyObject *
+_Py_type_getattro_impl(PyTypeObject *type, PyObject *name, int *suppress_missing_attribute);
+PyObject *
+_Py_type_getattro(PyTypeObject *type, PyObject *name);
 
 PyObject *_Py_slot_tp_getattro(PyObject *self, PyObject *name);
 PyObject *_Py_slot_tp_getattr_hook(PyObject *self, PyObject *name);

Misc/NEWS.d/next/Core and Builtins/2022-12-04-00-38-33.gh-issue-92216.CJXuWB.rst

@@ -0,0 +1 @@
+Improve the performance of :func:`hasattr` for type objects with a missing attribute.

Objects/object.c

@@ -939,7 +939,15 @@ _PyObject_LookupAttr(PyObject *v, PyObject *name, PyObject **result)
         }
         return 0;
     }
-    if (tp->tp_getattro != NULL) {
+    if (tp->tp_getattro == (getattrofunc)_Py_type_getattro) {
+        int supress_missing_attribute_exception = 0;
+        *result = _Py_type_getattro_impl((PyTypeObject*)v, name, &supress_missing_attribute_exception);
+        if (supress_missing_attribute_exception) {
+            // return 0 without having to clear the exception
+            return 0;
+        }
+    }
+    else if (tp->tp_getattro != NULL) {
         *result = (*tp->tp_getattro)(v, name);
     }
     else if (tp->tp_getattr != NULL) {

Objects/typeobject.c

@@ -4219,9 +4219,19 @@ _PyType_LookupId(PyTypeObject *type, _Py_Identifier *name)
 }
 
 /* This is similar to PyObject_GenericGetAttr(),
-   but uses _PyType_Lookup() instead of just looking in type->tp_dict. */
-static PyObject *
-type_getattro(PyTypeObject *type, PyObject *name)
+   but uses _PyType_Lookup() instead of just looking in type->tp_dict.
+
+   The argument suppress_missing_attribute is used to provide a
+   fast path for hasattr. The possible values are:
+
+   * NULL: do not suppress the exception
+   * Non-zero pointer: suppress the PyExc_AttributeError and
+     set *suppress_missing_attribute to 1 to signal we are returning NULL while
+     having suppressed the exception (other exceptions are not suppressed)
+
+   */
+PyObject *
+_Py_type_getattro_impl(PyTypeObject *type, PyObject *name, int * suppress_missing_attribute)
 {
     PyTypeObject *metatype = Py_TYPE(type);
     PyObject *meta_attribute, *attribute;
@@ -4301,12 +4311,25 @@ type_getattro(PyTypeObject *type, PyObject *name)
     }
 
     /* Give up */
-    PyErr_Format(PyExc_AttributeError,
-                 "type object '%.50s' has no attribute '%U'",
-                 type->tp_name, name);
+    if (suppress_missing_attribute == NULL) {
+        PyErr_Format(PyExc_AttributeError,
+                        "type object '%.50s' has no attribute '%U'",
+                        type->tp_name, name);
+    } else {
+        // signal the caller we have not set an PyExc_AttributeError and gave up
+        *suppress_missing_attribute = 1;
+    }
     return NULL;
 }
 
+/* This is similar to PyObject_GenericGetAttr(),
+   but uses _PyType_Lookup() instead of just looking in type->tp_dict. */
+PyObject *
+_Py_type_getattro(PyTypeObject *type, PyObject *name)
+{
+    return _Py_type_getattro_impl(type, name, NULL);
+}
+
 static int
 type_setattro(PyTypeObject *type, PyObject *name, PyObject *value)
 {
@@ -4798,7 +4821,7 @@ PyTypeObject PyType_Type = {
     0,                                          /* tp_hash */
     (ternaryfunc)type_call,                     /* tp_call */
     0,                                          /* tp_str */
-    (getattrofunc)type_getattro,                /* tp_getattro */
+    (getattrofunc)_Py_type_getattro,            /* tp_getattro */
     (setattrofunc)type_setattro,                /* tp_setattro */
     0,                                          /* tp_as_buffer */
     Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |