commit 069e81ab3da46c441335ca762c4333b7bd91861d
author Mark Shannon <mark@hotpy.org> Fri Apr 30 09:50:28 2021 +0100
committer GitHub <noreply@github.com> Fri Apr 30 09:50:28 2021 +0100
tree 02716907f4513a812cf2c72309cc4e6f133b3ab3
parent 2abbd8f2add5e80b86a965625b9a77ae94a101cd

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.

Modules/_abc.c

diff --git a/Modules/_abc.c b/Modules/_abc.c
index 0ddc2ab..39261dd 100644
--- a/Modules/_abc.c
+++ b/Modules/_abc.c
@@ -15,6 +15,7 @@ PyDoc_STRVAR(_abc__doc__,
 _Py_IDENTIFIER(__abstractmethods__);
 _Py_IDENTIFIER(__class__);
 _Py_IDENTIFIER(__dict__);
+_Py_IDENTIFIER(__abc_tpflags__);
 _Py_IDENTIFIER(__bases__);
 _Py_IDENTIFIER(_abc_impl);
 _Py_IDENTIFIER(__subclasscheck__);
@@ -417,6 +418,8 @@ compute_abstract_methods(PyObject *self)
     return ret;
 }
 
+#define COLLECTION_FLAGS (Py_TPFLAGS_SEQUENCE | Py_TPFLAGS_MAPPING)
+
 /*[clinic input]
 _abc._abc_init
 
@@ -446,6 +449,31 @@ _abc__abc_init(PyObject *module, PyObject *self)
         return NULL;
     }
     Py_DECREF(data);
+    /* If __abc_tpflags__ & COLLECTION_FLAGS is set, then set the corresponding bit(s)
+     * in the new class.
+     * Used by collections.abc.Sequence and collections.abc.Mapping to indicate
+     * their special status w.r.t. pattern matching. */
+    if (PyType_Check(self)) {
+        PyTypeObject *cls = (PyTypeObject *)self;
+        PyObject *flags = _PyDict_GetItemIdWithError(cls->tp_dict, &PyId___abc_tpflags__);
+        if (flags == NULL) {
+            if (PyErr_Occurred()) {
+                return NULL;
+            }
+        }
+        else {
+            if (PyLong_CheckExact(flags)) {
+                long val = PyLong_AsLong(flags);
+                if (val == -1 && PyErr_Occurred()) {
+                    return NULL;
+                }
+                ((PyTypeObject *)self)->tp_flags |= (val & COLLECTION_FLAGS);
+            }
+            if (_PyDict_DelItemId(cls->tp_dict, &PyId___abc_tpflags__) < 0) {
+                return NULL;
+            }
+        }
+    }
     Py_RETURN_NONE;
 }
 
@@ -499,6 +527,11 @@ _abc__abc_register_impl(PyObject *module, PyObject *self, PyObject *subclass)
     /* Invalidate negative cache */
     get_abc_state(module)->abc_invalidation_counter++;
 
+    if (PyType_Check(subclass) && PyType_Check(self) &&
+        !PyType_HasFeature((PyTypeObject *)subclass, Py_TPFLAGS_IMMUTABLETYPE))
+    {
+        ((PyTypeObject *)subclass)->tp_flags |= (((PyTypeObject *)self)->tp_flags & COLLECTION_FLAGS);
+    }
     Py_INCREF(subclass);
     return subclass;
 }

Modules/_collectionsmodule.c

diff --git a/Modules/_collectionsmodule.c b/Modules/_collectionsmodule.c
index 8b01a7f..9c8701a 100644
--- a/Modules/_collectionsmodule.c
+++ b/Modules/_collectionsmodule.c
@@ -1662,7 +1662,8 @@ static PyTypeObject deque_type = {
     PyObject_GenericGetAttr,            /* tp_getattro */
     0,                                  /* tp_setattro */
     0,                                  /* tp_as_buffer */
-    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC,
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE |
+    Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_SEQUENCE,
                                         /* tp_flags */
     deque_doc,                          /* tp_doc */
     (traverseproc)deque_traverse,       /* tp_traverse */

Modules/arraymodule.c

diff --git a/Modules/arraymodule.c b/Modules/arraymodule.c
index 367621f..d65c144 100644
--- a/Modules/arraymodule.c
+++ b/Modules/arraymodule.c
@@ -2848,7 +2848,8 @@ static PyType_Spec array_spec = {
     .name = "array.array",
     .basicsize = sizeof(arrayobject),
     .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE |
-              Py_TPFLAGS_IMMUTABLETYPE),
+              Py_TPFLAGS_IMMUTABLETYPE |
+              Py_TPFLAGS_SEQUENCE),
     .slots = array_slots,
 };