gh-94808: cover PyMapping_HasKeyString and PyMapping_HasKey (GH-98486)

(cherry picked from commit 5d30544)

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

Author: miss-islington

Lib/test/test_capi.py

@@ -403,6 +403,18 @@ def items(self):
         self.assertRaises(TypeError, _testcapi.get_mapping_values, bad_mapping)
         self.assertRaises(TypeError, _testcapi.get_mapping_items, bad_mapping)
 
+    def test_mapping_has_key(self):
+        dct = {'a': 1}
+        self.assertTrue(_testcapi.mapping_has_key(dct, 'a'))
+        self.assertFalse(_testcapi.mapping_has_key(dct, 'b'))
+
+        class SubDict(dict):
+            pass
+
+        dct2 = SubDict({'a': 1})
+        self.assertTrue(_testcapi.mapping_has_key(dct2, 'a'))
+        self.assertFalse(_testcapi.mapping_has_key(dct2, 'b'))
+
     @unittest.skipUnless(hasattr(_testcapi, 'negative_refcount'),
                          'need _testcapi.negative_refcount')
     def test_negative_refcount(self):

Modules/_testcapimodule.c

@@ -5348,6 +5348,40 @@ get_mapping_items(PyObject* self, PyObject *obj)
     return PyMapping_Items(obj);
 }
 
+static PyObject *
+test_mapping_has_key_string(PyObject *self, PyObject *Py_UNUSED(args))
+{
+    PyObject *context = PyDict_New();
+    PyObject *val = PyLong_FromLong(1);
+
+    // Since this uses `const char*` it is easier to test this in C:
+    PyDict_SetItemString(context, "a", val);
+    if (!PyMapping_HasKeyString(context, "a")) {
+        PyErr_SetString(PyExc_RuntimeError,
+                        "Existing mapping key does not exist");
+        return NULL;
+    }
+    if (PyMapping_HasKeyString(context, "b")) {
+        PyErr_SetString(PyExc_RuntimeError,
+                        "Missing mapping key exists");
+        return NULL;
+    }
+
+    Py_DECREF(val);
+    Py_DECREF(context);
+    Py_RETURN_NONE;
+}
+
+static PyObject *
+mapping_has_key(PyObject* self, PyObject *args)
+{
+    PyObject *context, *key;
+    if (!PyArg_ParseTuple(args, "OO", &context, &key)) {
+        return NULL;
+    }
+    return PyLong_FromLong(PyMapping_HasKey(context, key));
+}
+
 
 static PyObject *
 test_pythread_tss_key_state(PyObject *self, PyObject *args)
@@ -6382,6 +6416,8 @@ static PyMethodDef TestMethods[] = {
     {"get_mapping_keys", get_mapping_keys, METH_O},
     {"get_mapping_values", get_mapping_values, METH_O},
     {"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},
     {"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},