From 8dc2ec1513e90a8d23394f1c4ec3a07c4e057610 Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Wed, 30 Mar 2016 21:01:26 +0300
Subject: [PATCH] Issue #26492: Added additional tests for exhausted iterators
 of mutable sequences.

---
 Lib/test/list_tests.py | 11 +++++++++++
 Lib/test/test_bytes.py |  2 ++
 Lib/test/test_iter.py  | 11 +++++++++++
 3 files changed, 24 insertions(+)

diff --git a/Lib/test/list_tests.py b/Lib/test/list_tests.py
index 1adfc75b77a..f20fdc0a5f0 100644
--- a/Lib/test/list_tests.py
+++ b/Lib/test/list_tests.py
@@ -593,3 +593,14 @@ class CommonTest(seq_tests.CommonTest):
             def __iter__(self):
                 raise KeyboardInterrupt
         self.assertRaises(KeyboardInterrupt, list, F())
+
+    def test_exhausted_iterator(self):
+        a = self.type2test([1, 2, 3])
+        exhit = iter(a)
+        empit = iter(a)
+        for x in exhit:  # exhaust the iterator
+            next(empit)  # not exhausted
+        a.append(9)
+        self.assertEqual(list(exhit), [])
+        self.assertEqual(list(empit), [9])
+        self.assertEqual(a, self.type2test([1, 2, 3, 9]))
diff --git a/Lib/test/test_bytes.py b/Lib/test/test_bytes.py
index 1bd3a1ed9c4..01ba5e51c82 100644
--- a/Lib/test/test_bytes.py
+++ b/Lib/test/test_bytes.py
@@ -17,6 +17,7 @@ import unittest
 import test.support
 import test.string_tests
 import test.buffer_tests
+import test.list_tests
 from test.support import bigaddrspacetest, MAX_Py_ssize_t
 
 
@@ -1323,6 +1324,7 @@ class ByteArrayTest(BaseBytesTest, unittest.TestCase):
             b[:] = data
             self.assertEqual(list(it), [])
 
+    test_exhausted_iterator = test.list_tests.CommonTest.test_exhausted_iterator
 
 class AssortedBytesTest(unittest.TestCase):
     #
diff --git a/Lib/test/test_iter.py b/Lib/test/test_iter.py
index 54ddbaa5fdf..a91670b4a11 100644
--- a/Lib/test/test_iter.py
+++ b/Lib/test/test_iter.py
@@ -190,6 +190,17 @@ class TestCase(unittest.TestCase):
             self.assertTrue(isinstance(it, collections.abc.Iterator))
             self.assertEqual(list(it), [])
 
+    def test_mutating_seq_class_exhausted_iter(self):
+        a = SequenceClass(5)
+        exhit = iter(a)
+        empit = iter(a)
+        for x in exhit:  # exhaust the iterator
+            next(empit)  # not exhausted
+        a.n = 7
+        self.assertEqual(list(exhit), [])
+        self.assertEqual(list(empit), [5, 6])
+        self.assertEqual(list(a), [0, 1, 2, 3, 4, 5, 6])
+
     # Test a new_style class with __iter__ but no next() method
     def test_new_style_iter_class(self):
         class IterClass(object):