Issue #12050: zlib.decompressobj().decompress() now clears the unconsumed_tail

attribute when called without a max_length argument.

1 files changed, 9 insertions, 0 deletions

diff --git a/Lib/test/test_zlib.py b/Lib/test/test_zlib.py
index a003611a7c..7f631437b5 100644
--- a/Lib/test/test_zlib.py
+++ b/Lib/test/test_zlib.py
@@ -310,6 +310,15 @@ class CompressObjectTestCase(BaseCompressTestCase, unittest.TestCase):
         self.assertRaises(ValueError, dco.decompress, "", -1)
         self.assertEqual('', dco.unconsumed_tail)
 
+    def test_clear_unconsumed_tail(self):
+        # Issue #12050: calling decompress() without providing max_length
+        # should clear the unconsumed_tail attribute.
+        cdata = "x\x9cKLJ\x06\x00\x02M\x01"     # "abc"
+        dco = zlib.decompressobj()
+        ddata = dco.decompress(cdata, 1)
+        ddata += dco.decompress(dco.unconsumed_tail)
+        self.assertEqual(dco.unconsumed_tail, "")
+
     def test_flushes(self):
         # Test flush() with the various options, using all the
         # different levels in order to provide more variations.