TarFile.__init__() no longer fails if no name argument is passed and

the fileobj argument has no usable name attribute (e.g. StringIO).

(will backport to 2.5)

Lib/tarfile.py

@@ -1522,7 +1522,7 @@ class TarFile(object):
             if hasattr(fileobj, "mode"):
                 self._mode = fileobj.mode
             self._extfileobj = True
-        self.name = os.path.abspath(name)
+        self.name = os.path.abspath(name) if name else None
         self.fileobj = fileobj
 
         # Init attributes.

Lib/test/test_tarfile.py

@@ -141,11 +141,25 @@ class UstarReadTest(ReadTest):
 
 class MiscReadTest(ReadTest):
 
-    def test_no_filename(self):
+    def test_no_name_argument(self):
         fobj = open(self.tarname, "rb")
         tar = tarfile.open(fileobj=fobj, mode=self.mode)
         self.assertEqual(tar.name, os.path.abspath(fobj.name))
 
+    def test_no_name_attribute(self):
+        data = open(self.tarname, "rb").read()
+        fobj = StringIO.StringIO(data)
+        self.assertRaises(AttributeError, getattr, fobj, "name")
+        tar = tarfile.open(fileobj=fobj, mode=self.mode)
+        self.assertEqual(tar.name, None)
+
+    def test_empty_name_attribute(self):
+        data = open(self.tarname, "rb").read()
+        fobj = StringIO.StringIO(data)
+        fobj.name = ""
+        tar = tarfile.open(fileobj=fobj, mode=self.mode)
+        self.assertEqual(tar.name, None)
+
     def test_fail_comp(self):
         # For Gzip and Bz2 Tests: fail with a ReadError on an uncompressed file.
         if self.mode == "r:":

Misc/NEWS

@@ -240,6 +240,9 @@ Core and builtins
 Library
 -------
 
+- TarFile.__init__() no longer fails if no name argument is passed and
+  the fileobj argument has no usable name attribute (e.g. StringIO).
+
 - The functools module now provides 'reduce', for forward compatibility
   with Python 3000.