KeyError when syncing from mapping should be ignored; fixed unit test

Author: blhsing

Lib/test/test_builtin.py

@@ -1117,6 +1117,7 @@ def func_assign():
 
         def func_read():
             b = a + 1
+            a = 3
 
         for executor in eval, exec:
             with self.subTest(executor=executor.__name__):
@@ -1125,8 +1126,8 @@ def func_read():
                 self.assertEqual(ns, {'a': 1})
                 ns = {'a': 1}
                 executor(func_read.__code__, {}, ns, sync_fast_locals=True)
-                self.assertEqual(ns, {'a': 1, 'b': 2})
-        
+                self.assertEqual(ns, {'a': 3, 'b': 2})
+
     def test_filter(self):
         self.assertEqual(list(filter(lambda c: 'a' <= c <= 'z', 'Hello World')), list('elloorld'))
         self.assertEqual(list(filter(None, [1, 'hello', [], [3], '', None, 9, 0])), [1, 'hello', [3], 9])

Python/ceval.c

@@ -1542,6 +1542,9 @@ _PyEval_SyncLocalsToFast(_PyInterpreterFrame *frame)
         if (value != NULL) {
             frame->localsplus[i] = PyStackRef_FromPyObjectSteal(value);
         }
+        else if (PyErr_ExceptionMatches(PyExc_KeyError)) {
+            PyErr_Clear();
+        }
         else {
             return -1;
         }