bpo-46903: Handle str-subclasses in virtual instance dictionaries. (GH-31658)

5 files changed, 46 insertions, 10 deletions

diff --git a/Include/internal/pycore_code.h b/Include/internal/pycore_code.h
index 25c31a1..2e03358 100644
--- a/Include/internal/pycore_code.h
+++ b/Include/internal/pycore_code.h
@@ -398,6 +398,7 @@ typedef struct _object_stats {
     uint64_t dict_materialized_on_request;
     uint64_t dict_materialized_new_key;
     uint64_t dict_materialized_too_big;
+    uint64_t dict_materialized_str_subclass;
 } ObjectStats;
 
 typedef struct _stats {
diff --git a/Lib/test/test_unicode.py b/Lib/test/test_unicode.py
index 8e4e648..e97f971 100644
--- a/Lib/test/test_unicode.py
+++ b/Lib/test/test_unicode.py
@@ -3044,6 +3044,30 @@ class StringModuleTest(unittest.TestCase):
             ]])
         self.assertRaises(TypeError, _string.formatter_field_name_split, 1)
 
+    def test_str_subclass_attr(self):
+
+        name = StrSubclass("name")
+        name2 = StrSubclass("name2")
+        class Bag:
+            pass
+
+        o = Bag()
+        with self.assertRaises(AttributeError):
+            delattr(o, name)
+        setattr(o, name, 1)
+        self.assertEquals(o.name, 1)
+        o.name = 2
+        self.assertEquals(list(o.__dict__), [name])
+
+        with self.assertRaises(AttributeError):
+            delattr(o, name2)
+        with self.assertRaises(AttributeError):
+            del o.name2
+        setattr(o, name2, 3)
+        self.assertEquals(o.name2, 3)
+        o.name2 = 4
+        self.assertEquals(list(o.__dict__), [name, name2])
+
 
 if __name__ == "__main__":
     unittest.main()
diff --git a/Misc/NEWS.d/next/Core and Builtins/2022-03-03-12-02-41.bpo-46903.OzgaFZ.rst b/Misc/NEWS.d/next/Core and Builtins/2022-03-03-12-02-41.bpo-46903.OzgaFZ.rst
new file mode 100644
index 0000000..f6120ef
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2022-03-03-12-02-41.bpo-46903.OzgaFZ.rst
@@ -0,0 +1,2 @@
+Make sure that str subclasses can be used as attribute names for instances
+with virtual dictionaries. Fixes regression in 3.11alpha
diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index d8bf164..635a738 100644
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -5427,23 +5427,26 @@ int
 _PyObject_StoreInstanceAttribute(PyObject *obj, PyDictValues *values,
                               PyObject *name, PyObject *value)
 {
-    assert(PyUnicode_CheckExact(name));
     PyDictKeysObject *keys = CACHED_KEYS(Py_TYPE(obj));
     assert(keys != NULL);
     assert(values != NULL);
     assert(Py_TYPE(obj)->tp_flags & Py_TPFLAGS_MANAGED_DICT);
-    Py_ssize_t ix = insert_into_dictkeys(keys, name);
+    Py_ssize_t ix = DKIX_EMPTY;
+    if (PyUnicode_CheckExact(name)) {
+        ix = insert_into_dictkeys(keys, name);
+    }
     if (ix == DKIX_EMPTY) {
-        if (value == NULL) {
-            PyErr_SetObject(PyExc_AttributeError, name);
-            return -1;
-        }
 #ifdef Py_STATS
-        if (shared_keys_usable_size(keys) == SHARED_KEYS_MAX_SIZE) {
-            OBJECT_STAT_INC(dict_materialized_too_big);
+        if (PyUnicode_CheckExact(name)) {
+            if (shared_keys_usable_size(keys) == SHARED_KEYS_MAX_SIZE) {
+                OBJECT_STAT_INC(dict_materialized_too_big);
+            }
+            else {
+                OBJECT_STAT_INC(dict_materialized_new_key);
+            }
         }
         else {
-            OBJECT_STAT_INC(dict_materialized_new_key);
+            OBJECT_STAT_INC(dict_materialized_str_subclass);
         }
 #endif
         PyObject *dict = make_dict_from_instance_attributes(keys, values);
@@ -5452,7 +5455,12 @@ _PyObject_StoreInstanceAttribute(PyObject *obj, PyDictValues *values,
         }
         *_PyObject_ValuesPointer(obj) = NULL;
         *_PyObject_ManagedDictPointer(obj) = dict;
-        return PyDict_SetItem(dict, name, value);
+        if (value == NULL) {
+            return PyDict_DelItem(dict, name);
+        }
+        else {
+            return PyDict_SetItem(dict, name, value);
+        }
     }
     PyObject *old_value = values->values[ix];
     Py_XINCREF(value);
diff --git a/Python/specialize.c b/Python/specialize.c
index 66dce8c..912b9e2 100644
--- a/Python/specialize.c
+++ b/Python/specialize.c
@@ -221,6 +221,7 @@ print_object_stats(FILE *out, ObjectStats *stats)
     fprintf(out, "Object materialize dict (on request): %" PRIu64 "\n", stats->dict_materialized_on_request);
     fprintf(out, "Object materialize dict (new key): %" PRIu64 "\n", stats->dict_materialized_new_key);
     fprintf(out, "Object materialize dict (too big): %" PRIu64 "\n", stats->dict_materialized_too_big);
+    fprintf(out, "Object materialize dict (str subclass): %" PRIu64 "\n", stats->dict_materialized_str_subclass);
 }
 
 static void