Issue #7232: Add support for the context manager protocol

to the TarFile class.

Lib/test/test_tarfile.py

@@ -1292,6 +1292,65 @@ class LimitsTest(unittest.TestCase):
         tarinfo.tobuf(tarfile.PAX_FORMAT)
 
 
+class ContextManagerTest(unittest.TestCase):
+
+    def test_basic(self):
+        with tarfile.open(tarname) as tar:
+            self.assertFalse(tar.closed, "closed inside runtime context")
+        self.assertTrue(tar.closed, "context manager failed")
+
+    def test_closed(self):
+        # The __enter__() method is supposed to raise IOError
+        # if the TarFile object is already closed.
+        tar = tarfile.open(tarname)
+        tar.close()
+        with self.assertRaises(IOError):
+            with tar:
+                pass
+
+    def test_exception(self):
+        # Test if the IOError exception is passed through properly.
+        with self.assertRaises(Exception) as exc:
+            with tarfile.open(tarname) as tar:
+                raise IOError
+        self.assertIsInstance(exc.exception, IOError,
+                              "wrong exception raised in context manager")
+        self.assertTrue(tar.closed, "context manager failed")
+
+    def test_no_eof(self):
+        # __exit__() must not write end-of-archive blocks if an
+        # exception was raised.
+        try:
+            with tarfile.open(tmpname, "w") as tar:
+                raise Exception
+        except:
+            pass
+        self.assertEqual(os.path.getsize(tmpname), 0,
+                "context manager wrote an end-of-archive block")
+        self.assertTrue(tar.closed, "context manager failed")
+
+    def test_eof(self):
+        # __exit__() must write end-of-archive blocks, i.e. call
+        # TarFile.close() if there was no error.
+        with tarfile.open(tmpname, "w"):
+            pass
+        self.assertNotEqual(os.path.getsize(tmpname), 0,
+                "context manager wrote no end-of-archive block")
+
+    def test_fileobj(self):
+        # Test that __exit__() did not close the external file
+        # object.
+        fobj = open(tmpname, "wb")
+        try:
+            with tarfile.open(fileobj=fobj, mode="w") as tar:
+                raise Exception
+        except:
+            pass
+        self.assertFalse(fobj.closed, "external file object was closed")
+        self.assertTrue(tar.closed, "context manager failed")
+        fobj.close()
+
+
 class GzipMiscReadTest(MiscReadTest):
     tarname = gzipname
     mode = "r:gz"
@@ -1371,6 +1430,7 @@ def test_main():
         PaxUnicodeTest,
         AppendTest,
         LimitsTest,
+        ContextManagerTest,
     ]
 
     if hasattr(os, "link"):