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

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

(backported from r57616)

Lib/tarfile.py

@@ -1044,24 +1044,21 @@ class TarFile(object):
            can be determined, `mode' is overridden by `fileobj's mode.
            `fileobj' is not closed, when TarFile is closed.
         """
-        self.name = name
-        if self.name is not None:
-            self.name = os.path.abspath(name)
-
         if len(mode) > 1 or mode not in "raw":
             raise ValueError("mode must be 'r', 'a' or 'w'")
         self._mode = mode
         self.mode = {"r": "rb", "a": "r+b", "w": "wb"}[mode]
 
         if not fileobj:
-            fileobj = file(self.name, self.mode)
+            fileobj = file(name, self.mode)
             self._extfileobj = False
         else:
-            if self.name is None and hasattr(fileobj, "name"):
-                self.name = os.path.abspath(fileobj.name)
+            if name is None and hasattr(fileobj, "name"):
+                name = fileobj.name
             if hasattr(fileobj, "mode"):
                 self.mode = fileobj.mode
             self._extfileobj = True
+        self.name = os.path.abspath(name) if name else None
         self.fileobj = fileobj
 
         # Init datastructures

Lib/test/test_tarfile.py

@@ -642,11 +642,25 @@ class OpenFileobjTest(BaseTest):
         except tarfile.ReadError:
             self.assertEqual(fobj.tell(), 0, "fileobj's position has moved")
 
-    def test_fileobj(self):
-        # Test for SF bug #1695229, opening a tarfile without
-        # a name argument.
-        tarfile.open(mode="r", fileobj=open(tarname("")))
-        tarfile.TarFile(mode="r", fileobj=open(tarname("")))
+    def test_no_name_argument(self):
+        fobj = open(testtar, "rb")
+        tar = tarfile.open(fileobj=fobj, mode="r")
+        self.assertEqual(tar.name, os.path.abspath(fobj.name))
+
+    def test_no_name_attribute(self):
+        data = open(testtar, "rb").read()
+        fobj = StringIO.StringIO(data)
+        self.assertRaises(AttributeError, getattr, fobj, "name")
+        tar = tarfile.open(fileobj=fobj, mode="r")
+        self.assertEqual(tar.name, None)
+
+    def test_empty_name_attribute(self):
+        data = open(testtar, "rb").read()
+        fobj = StringIO.StringIO(data)
+        fobj.name = ""
+        tar = tarfile.open(fileobj=fobj, mode="r")
+        self.assertEqual(tar.name, None)
+
 
 if bz2:
     # Bzip2 TestCases

Misc/NEWS

@@ -26,6 +26,9 @@ 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).
+
 - Reverted the fix for bug #1548891 because it broke compatibility with
   arbitrary read buffers. Added a note in the documentation.