Patch #1413711: Certain patterns of differences were making difflib

touch the recursion limit. The applied patch inlines the recursive
__helper method in a non-recursive way.

1 files changed, 9 insertions, 0 deletions

diff --git a/Lib/test/test_difflib.py b/Lib/test/test_difflib.py
index c0bf66e..52feef0 100644
--- a/Lib/test/test_difflib.py
+++ b/Lib/test/test_difflib.py
@@ -2,6 +2,7 @@ import difflib
 from test.test_support import run_unittest, findfile
 import unittest
 import doctest
+import sys
 
 class TestSFbugs(unittest.TestCase):
 
@@ -143,6 +144,14 @@ class TestSFpatches(unittest.TestCase):
 
         self.assertEqual(actual,expect)
 
+    def test_recursion_limit(self):
+        # Check if the problem described in patch #1413711 exists.
+        limit = sys.getrecursionlimit()
+        old = [(i%2 and "K:%d" or "V:A:%d") % i for i in range(limit*2)]
+        new = [(i%2 and "K:%d" or "V:B:%d") % i for i in range(limit*2)]
+        difflib.SequenceMatcher(None, old, new).get_opcodes()
+
+
 Doctests = doctest.DocTestSuite(difflib)
 
 run_unittest(TestSFpatches, TestSFbugs, Doctests)