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bpo-43977: Use tp_flags for collection matching (GH-25723)
* Add Py_TPFLAGS_SEQUENCE and Py_TPFLAGS_MAPPING, add to all relevant standard builtin classes. * Set relevant flags on collections.abc.Sequence and Mapping. * Use flags in MATCH_SEQUENCE and MATCH_MAPPING opcodes. * Inherit Py_TPFLAGS_SEQUENCE and Py_TPFLAGS_MAPPING. * Add NEWS * Remove interpreter-state map_abc and seq_abc fields.
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-83
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16 files changed

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-83
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‎Include/internal/pycore_interp.h‎

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@@ -247,10 +247,6 @@ struct _is {
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// importlib module
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PyObject *importlib;
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250-
// Kept handy for pattern matching:
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PyObject *map_abc; // _collections_abc.Mapping
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PyObject *seq_abc; // _collections_abc.Sequence
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/* Used in Modules/_threadmodule.c. */
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long num_threads;
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/* Support for runtime thread stack size tuning.

‎Include/object.h‎

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@@ -320,6 +320,13 @@ Code can use PyType_HasFeature(type_ob, flag_value) to test whether the
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given type object has a specified feature.
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*/
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#ifndef Py_LIMITED_API
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/* Set if instances of the type object are treated as sequences for pattern matching */
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#define Py_TPFLAGS_SEQUENCE (1 << 5)
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/* Set if instances of the type object are treated as mappings for pattern matching */
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#define Py_TPFLAGS_MAPPING (1 << 6)
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#endif
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/* Set if the type object is immutable: type attributes cannot be set nor deleted */
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#define Py_TPFLAGS_IMMUTABLETYPE (1UL << 8)
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‎Lib/_collections_abc.py‎

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@@ -793,7 +793,6 @@ def __isub__(self, it):
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### MAPPINGS ###
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class Mapping(Collection):
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"""A Mapping is a generic container for associating key/value
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pairs.
@@ -804,6 +803,9 @@ class Mapping(Collection):
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__slots__ = ()
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# Tell ABCMeta.__new__ that this class should have TPFLAGS_MAPPING set.
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__abc_tpflags__ = 1 << 6 # Py_TPFLAGS_MAPPING
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@abstractmethod
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def __getitem__(self, key):
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raise KeyError
@@ -842,7 +844,6 @@ def __eq__(self, other):
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__reversed__ = None
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Mapping.register(mappingproxy)
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@@ -1011,7 +1012,6 @@ def setdefault(self, key, default=None):
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### SEQUENCES ###
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class Sequence(Reversible, Collection):
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"""All the operations on a read-only sequence.
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@@ -1021,6 +1021,9 @@ class Sequence(Reversible, Collection):
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__slots__ = ()
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# Tell ABCMeta.__new__ that this class should have TPFLAGS_SEQUENCE set.
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__abc_tpflags__ = 1 << 5 # Py_TPFLAGS_SEQUENCE
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@abstractmethod
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def __getitem__(self, index):
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raise IndexError
@@ -1072,7 +1075,6 @@ def count(self, value):
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'S.count(value) -> integer -- return number of occurrences of value'
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return sum(1 for v in self if v is value or v == value)
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Sequence.register(tuple)
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Sequence.register(str)
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Sequence.register(range)

‎Misc/NEWS.d/next/Core and Builtins/2021-04-29-17-40-25.bpo-43977.FrQhge.rst‎

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@@ -0,0 +1,2 @@
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Use :c:member:`~PyTypeObject.tp_flags` on the class object to determine if the subject is a sequence
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or mapping when pattern matching. Avoids the need to import :mod:`collections.abc` when pattern matching.

‎Modules/_abc.c‎

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@@ -15,6 +15,7 @@ PyDoc_STRVAR(_abc__doc__,
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_Py_IDENTIFIER(__abstractmethods__);
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_Py_IDENTIFIER(__class__);
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_Py_IDENTIFIER(__dict__);
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_Py_IDENTIFIER(__abc_tpflags__);
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_Py_IDENTIFIER(__bases__);
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_Py_IDENTIFIER(_abc_impl);
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_Py_IDENTIFIER(__subclasscheck__);
@@ -417,6 +418,8 @@ compute_abstract_methods(PyObject *self)
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return ret;
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}
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#define COLLECTION_FLAGS (Py_TPFLAGS_SEQUENCE | Py_TPFLAGS_MAPPING)
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/*[clinic input]
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_abc._abc_init
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@@ -446,6 +449,31 @@ _abc__abc_init(PyObject *module, PyObject *self)
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return NULL;
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}
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Py_DECREF(data);
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/* If __abc_tpflags__ & COLLECTION_FLAGS is set, then set the corresponding bit(s)
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* in the new class.
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* Used by collections.abc.Sequence and collections.abc.Mapping to indicate
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* their special status w.r.t. pattern matching. */
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if (PyType_Check(self)) {
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PyTypeObject *cls = (PyTypeObject *)self;
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PyObject *flags = _PyDict_GetItemIdWithError(cls->tp_dict, &PyId___abc_tpflags__);
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if (flags == NULL) {
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if (PyErr_Occurred()) {
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return NULL;
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}
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}
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else {
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if (PyLong_CheckExact(flags)) {
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long val = PyLong_AsLong(flags);
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if (val == -1 && PyErr_Occurred()) {
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return NULL;
469+
}
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((PyTypeObject *)self)->tp_flags |= (val & COLLECTION_FLAGS);
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}
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if (_PyDict_DelItemId(cls->tp_dict, &PyId___abc_tpflags__) < 0) {
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return NULL;
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}
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}
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}
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Py_RETURN_NONE;
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}
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@@ -499,6 +527,11 @@ _abc__abc_register_impl(PyObject *module, PyObject *self, PyObject *subclass)
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/* Invalidate negative cache */
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get_abc_state(module)->abc_invalidation_counter++;
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if (PyType_Check(subclass) && PyType_Check(self) &&
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!PyType_HasFeature((PyTypeObject *)subclass, Py_TPFLAGS_IMMUTABLETYPE))
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{
533+
((PyTypeObject *)subclass)->tp_flags |= (((PyTypeObject *)self)->tp_flags & COLLECTION_FLAGS);
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}
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Py_INCREF(subclass);
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return subclass;
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}

‎Modules/_collectionsmodule.c‎

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@@ -1662,7 +1662,8 @@ static PyTypeObject deque_type = {
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PyObject_GenericGetAttr, /* tp_getattro */
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0, /* tp_setattro */
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0, /* tp_as_buffer */
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Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC,
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Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE |
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Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_SEQUENCE,
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/* tp_flags */
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deque_doc, /* tp_doc */
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(traverseproc)deque_traverse, /* tp_traverse */

‎Modules/arraymodule.c‎

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@@ -2848,7 +2848,8 @@ static PyType_Spec array_spec = {
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.name = "array.array",
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.basicsize = sizeof(arrayobject),
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.flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE |
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Py_TPFLAGS_IMMUTABLETYPE),
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Py_TPFLAGS_IMMUTABLETYPE |
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Py_TPFLAGS_SEQUENCE),
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.slots = array_slots,
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};
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‎Objects/descrobject.c‎

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@@ -1852,7 +1852,8 @@ PyTypeObject PyDictProxy_Type = {
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PyObject_GenericGetAttr, /* tp_getattro */
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0, /* tp_setattro */
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0, /* tp_as_buffer */
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Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC, /* tp_flags */
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Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
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Py_TPFLAGS_MAPPING, /* tp_flags */
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0, /* tp_doc */
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mappingproxy_traverse, /* tp_traverse */
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0, /* tp_clear */

‎Objects/dictobject.c‎

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@@ -3553,7 +3553,7 @@ PyTypeObject PyDict_Type = {
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0, /* tp_as_buffer */
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Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
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Py_TPFLAGS_BASETYPE | Py_TPFLAGS_DICT_SUBCLASS |
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_Py_TPFLAGS_MATCH_SELF, /* tp_flags */
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_Py_TPFLAGS_MATCH_SELF | Py_TPFLAGS_MAPPING, /* tp_flags */
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dictionary_doc, /* tp_doc */
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dict_traverse, /* tp_traverse */
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dict_tp_clear, /* tp_clear */

‎Objects/listobject.c‎

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@@ -3053,7 +3053,7 @@ PyTypeObject PyList_Type = {
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0, /* tp_as_buffer */
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Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
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Py_TPFLAGS_BASETYPE | Py_TPFLAGS_LIST_SUBCLASS |
3056-
_Py_TPFLAGS_MATCH_SELF, /* tp_flags */
3056+
_Py_TPFLAGS_MATCH_SELF | Py_TPFLAGS_SEQUENCE, /* tp_flags */
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list___init____doc__, /* tp_doc */
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(traverseproc)list_traverse, /* tp_traverse */
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(inquiry)_list_clear, /* tp_clear */

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