gh-94808: add tests covering PySequence_{Set,Del}Slice (GH-99123)

(cherry picked from commit c5c4077)

Co-authored-by: Nikita Sobolev <mail@sobolevn.me>

Author: miss-islington

Lib/test/test_capi.py

@@ -415,6 +415,86 @@ class SubDict(dict):
         self.assertTrue(_testcapi.mapping_has_key(dct2, 'a'))
         self.assertFalse(_testcapi.mapping_has_key(dct2, 'b'))
 
+    def test_sequence_set_slice(self):
+        # Correct case:
+        data = [1, 2, 3, 4, 5]
+        data_copy = data.copy()
+
+        _testcapi.sequence_set_slice(data, 1, 3, [8, 9])
+        data_copy[1:3] = [8, 9]
+        self.assertEqual(data, data_copy)
+        self.assertEqual(data, [1, 8, 9, 4, 5])
+
+        # Custom class:
+        class Custom:
+            def __setitem__(self, index, value):
+                self.index = index
+                self.value = value
+
+        c = Custom()
+        _testcapi.sequence_set_slice(c, 0, 5, 'abc')
+        self.assertEqual(c.index, slice(0, 5))
+        self.assertEqual(c.value, 'abc')
+
+        # Immutable sequences must raise:
+        bad_seq1 = (1, 2, 3, 4)
+        with self.assertRaises(TypeError):
+            _testcapi.sequence_set_slice(bad_seq1, 1, 3, (8, 9))
+        self.assertEqual(bad_seq1, (1, 2, 3, 4))
+
+        bad_seq2 = 'abcd'
+        with self.assertRaises(TypeError):
+            _testcapi.sequence_set_slice(bad_seq2, 1, 3, 'xy')
+        self.assertEqual(bad_seq2, 'abcd')
+
+        # Not a sequence:
+        with self.assertRaises(TypeError):
+            _testcapi.sequence_set_slice(None, 1, 3, 'xy')
+
+        mapping = {1: 'a', 2: 'b', 3: 'c'}
+        with self.assertRaises(TypeError):
+            _testcapi.sequence_set_slice(mapping, 1, 3, 'xy')
+        self.assertEqual(mapping, {1: 'a', 2: 'b', 3: 'c'})
+
+    def test_sequence_del_slice(self):
+        # Correct case:
+        data = [1, 2, 3, 4, 5]
+        data_copy = data.copy()
+
+        _testcapi.sequence_del_slice(data, 1, 3)
+        del data_copy[1:3]
+        self.assertEqual(data, data_copy)
+        self.assertEqual(data, [1, 4, 5])
+
+        # Custom class:
+        class Custom:
+            def __delitem__(self, index):
+                self.index = index
+
+        c = Custom()
+        _testcapi.sequence_del_slice(c, 0, 5)
+        self.assertEqual(c.index, slice(0, 5))
+
+        # Immutable sequences must raise:
+        bad_seq1 = (1, 2, 3, 4)
+        with self.assertRaises(TypeError):
+            _testcapi.sequence_del_slice(bad_seq1, 1, 3)
+        self.assertEqual(bad_seq1, (1, 2, 3, 4))
+
+        bad_seq2 = 'abcd'
+        with self.assertRaises(TypeError):
+            _testcapi.sequence_del_slice(bad_seq2, 1, 3)
+        self.assertEqual(bad_seq2, 'abcd')
+
+        # Not a sequence:
+        with self.assertRaises(TypeError):
+            _testcapi.sequence_del_slice(None, 1, 3)
+
+        mapping = {1: 'a', 2: 'b', 3: 'c'}
+        with self.assertRaises(TypeError):
+            _testcapi.sequence_del_slice(mapping, 1, 3)
+        self.assertEqual(mapping, {1: 'a', 2: 'b', 3: 'c'})
+
     @unittest.skipUnless(hasattr(_testcapi, 'negative_refcount'),
                          'need _testcapi.negative_refcount')
     def test_negative_refcount(self):

Modules/_testcapimodule.c

@@ -5382,6 +5382,37 @@ mapping_has_key(PyObject* self, PyObject *args)
     return PyLong_FromLong(PyMapping_HasKey(context, key));
 }
 
+static PyObject *
+sequence_set_slice(PyObject* self, PyObject *args)
+{
+    PyObject *sequence, *obj;
+    Py_ssize_t i1, i2;
+    if (!PyArg_ParseTuple(args, "OnnO", &sequence, &i1, &i2, &obj)) {
+        return NULL;
+    }
+
+    int res = PySequence_SetSlice(sequence, i1, i2, obj);
+    if (res == -1) {
+        return NULL;
+    }
+    Py_RETURN_NONE;
+}
+
+static PyObject *
+sequence_del_slice(PyObject* self, PyObject *args)
+{
+    PyObject *sequence;
+    Py_ssize_t i1, i2;
+    if (!PyArg_ParseTuple(args, "Onn", &sequence, &i1, &i2)) {
+        return NULL;
+    }
+
+    int res = PySequence_DelSlice(sequence, i1, i2);
+    if (res == -1) {
+        return NULL;
+    }
+    Py_RETURN_NONE;
+}
 
 static PyObject *
 test_pythread_tss_key_state(PyObject *self, PyObject *args)
@@ -6424,6 +6455,8 @@ static PyMethodDef TestMethods[] = {
     {"get_mapping_items", get_mapping_items, METH_O},
     {"test_mapping_has_key_string", test_mapping_has_key_string, METH_NOARGS},
     {"mapping_has_key", mapping_has_key, METH_VARARGS},
+    {"sequence_set_slice", sequence_set_slice, METH_VARARGS},
+    {"sequence_del_slice", sequence_del_slice, METH_VARARGS},
     {"test_pythread_tss_key_state", test_pythread_tss_key_state, METH_VARARGS},
     {"hamt", new_hamt, METH_NOARGS},
     {"bad_get", _PyCFunction_CAST(bad_get), METH_FASTCALL},