add test

Author: ashm-dev

Lib/test/test_json/test_dump.py

@@ -65,6 +65,39 @@ def __lt__(self, o):
         d[1337] = "true.dat"
         self.assertEqual(self.dumps(d, sort_keys=True), '{"1337": "true.dat"}')
 
+    def test_mutate_items_during_encode(self):
+        c_make_encoder = getattr(self.json.encoder, 'c_make_encoder', None)
+        if c_make_encoder is None:
+            self.skipTest("c_make_encoder not available")
+
+        cache = []
+
+        class BadDict(dict):
+            def __init__(self):
+                super().__init__(real=1)
+
+            def items(self):
+                entries = [("boom", object())]
+                cache.append(entries)
+                return entries
+
+        def encode_str(obj):
+            if cache:
+                cache.pop().clear()
+            return '"x"'
+
+        encoder = c_make_encoder(
+            None, lambda o: "null",
+            encode_str, None,
+            ": ", ", ", False,
+            False, True
+        )
+
+        try:
+            encoder(BadDict(), 0)
+        except (ValueError, RuntimeError, SystemError):
+            pass
+
 
 class TestPyDump(TestDump, PyTest): pass