bpo-37540: vectorcall: keyword names must be strings (GH-14682)

The fact that keyword names are strings is now part of the vectorcall and `METH_FASTCALL` protocols. The biggest concrete change is that `_PyStack_UnpackDict` now checks that and raises `TypeError` if not.

CC @markshannon @vstinner 


https://bugs.python.org/issue37540

2 files changed, 12 insertions, 32 deletions

diff --git a/Python/ceval.c b/Python/ceval.c
index 7c7359166d..ee03350031 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -3504,7 +3504,9 @@ main_loop:
             PyObject **sp, *res, *names;
 
             names = POP();
-            assert(PyTuple_CheckExact(names) && PyTuple_GET_SIZE(names) <= oparg);
+            assert(PyTuple_Check(names));
+            assert(PyTuple_GET_SIZE(names) <= oparg);
+            /* We assume without checking that names contains only strings */
             sp = stack_pointer;
             res = call_function(tstate, &sp, oparg, names);
             stack_pointer = sp;
@@ -5372,20 +5374,12 @@ format_kwargs_error(PyThreadState *tstate, PyObject *func, PyObject *kwargs)
         _PyErr_Fetch(tstate, &exc, &val, &tb);
         if (val && PyTuple_Check(val) && PyTuple_GET_SIZE(val) == 1) {
             PyObject *key = PyTuple_GET_ITEM(val, 0);
-            if (!PyUnicode_Check(key)) {
-                _PyErr_Format(tstate, PyExc_TypeError,
-                              "%.200s%.200s keywords must be strings",
-                              PyEval_GetFuncName(func),
-                              PyEval_GetFuncDesc(func));
-            }
-            else {
-                _PyErr_Format(tstate, PyExc_TypeError,
-                              "%.200s%.200s got multiple "
-                              "values for keyword argument '%U'",
-                              PyEval_GetFuncName(func),
-                              PyEval_GetFuncDesc(func),
-                              key);
-            }
+            _PyErr_Format(tstate, PyExc_TypeError,
+                          "%.200s%.200s got multiple "
+                          "values for keyword argument '%S'",
+                          PyEval_GetFuncName(func),
+                          PyEval_GetFuncDesc(func),
+                          key);
             Py_XDECREF(exc);
             Py_XDECREF(val);
             Py_XDECREF(tb);
diff --git a/Python/getargs.c b/Python/getargs.c
index 59f0fdabb7..cdc16d4730 100644
--- a/Python/getargs.c
+++ b/Python/getargs.c
@@ -2043,11 +2043,7 @@ find_keyword(PyObject *kwnames, PyObject *const *kwstack, PyObject *key)
         if (kwname == key) {
             return kwstack[i];
         }
-        if (!PyUnicode_Check(kwname)) {
-            /* ignore non-string keyword keys:
-               an error will be raised below */
-            continue;
-        }
+        assert(PyUnicode_Check(kwname));
         if (_PyUnicode_EQ(kwname, key)) {
             return kwstack[i];
         }
@@ -2275,16 +2271,11 @@ vgetargskeywordsfast_impl(PyObject *const *args, Py_ssize_t nargs,
                 j++;
             }
 
-            if (!PyUnicode_Check(keyword)) {
-                PyErr_SetString(PyExc_TypeError,
-                                "keywords must be strings");
-                return cleanreturn(0, &freelist);
-            }
             match = PySequence_Contains(kwtuple, keyword);
             if (match <= 0) {
                 if (!match) {
                     PyErr_Format(PyExc_TypeError,
-                                 "'%U' is an invalid keyword "
+                                 "'%S' is an invalid keyword "
                                  "argument for %.200s%s",
                                  keyword,
                                  (parser->fname == NULL) ? "this function" : parser->fname,
@@ -2505,16 +2496,11 @@ _PyArg_UnpackKeywords(PyObject *const *args, Py_ssize_t nargs,
                 j++;
             }
 
-            if (!PyUnicode_Check(keyword)) {
-                PyErr_SetString(PyExc_TypeError,
-                                "keywords must be strings");
-                return NULL;
-            }
             match = PySequence_Contains(kwtuple, keyword);
             if (match <= 0) {
                 if (!match) {
                     PyErr_Format(PyExc_TypeError,
-                                 "'%U' is an invalid keyword "
+                                 "'%S' is an invalid keyword "
                                  "argument for %.200s%s",
                                  keyword,
                                  (parser->fname == NULL) ? "this function" : parser->fname,