# HG changeset patch
# User Philip Jenvey <pjenvey@underboss.org>
# Date 1396901856 25200
#      Mon Apr 07 13:17:36 2014 -0700
# Node ID b1cc800ba1defdd424e779100f5a5973c51aec2f
# Parent  34ace7eb67e9de12d90fe84022d3e0d063488f84
issue21173: trigger WeakKeyDictionary.__len__ raising a ValueError

diff -r 34ace7eb67e9 -r b1cc800ba1de Lib/test/test_weakref.py
--- a/Lib/test/test_weakref.py	Mon Apr 07 11:20:22 2014 +0200
+++ b/Lib/test/test_weakref.py	Mon Apr 07 13:17:36 2014 -0700
@@ -1319,6 +1319,22 @@
                 it = None           # should commit all removals
         self.check_weak_destroy_and_mutate_while_iterating(dict, testcontext)
 
+    def test_weak_keys_len_destroy_while_iterating(self):
+        it = None
+        dict, objects = self.make_weak_keyed_dict()
+        @contextlib.contextmanager
+        def testcontext():
+            nonlocal it
+            it = iter(dict.items())
+            next(it)
+            # Schedule a key/value for removal and recreate it
+            v = objects.pop().arg
+            gc.collect()      # just in case
+            yield Object(v), v
+        with testcontext() as (k, v):
+            dict.clear()
+        self.assertEqual(len(dict), 0)
+
     def test_weak_values_destroy_while_iterating(self):
         # Issue #7105: iterators shouldn't crash when a key is implicitly removed
         dict, objects = self.make_weak_valued_dict()