Issue #23421: Fixed compression in tarfile CLI. Patch by wdv4758h.

Lib/tarfile.py

@@ -2494,16 +2494,16 @@ def main():
         _, ext = os.path.splitext(tar_name)
         compressions = {
             # gz
-            'gz': 'gz',
-            'tgz': 'gz',
+            '.gz': 'gz',
+            '.tgz': 'gz',
             # xz
-            'xz': 'xz',
-            'txz': 'xz',
+            '.xz': 'xz',
+            '.txz': 'xz',
             # bz2
-            'bz2': 'bz2',
-            'tbz': 'bz2',
-            'tbz2': 'bz2',
-            'tb2': 'bz2',
+            '.bz2': 'bz2',
+            '.tbz': 'bz2',
+            '.tbz2': 'bz2',
+            '.tb2': 'bz2',
         }
         tar_mode = 'w:' + compressions[ext] if ext in compressions else 'w'
         tar_files = args.create

Lib/test/test_tarfile.py

@@ -2006,6 +2006,21 @@ class CommandLineTest(unittest.TestCase):
         finally:
             support.unlink(tar_name)
 
+    def test_create_command_compressed(self):
+        files = [support.findfile('tokenize_tests.txt'),
+                 support.findfile('tokenize_tests-no-coding-cookie-'
+                                  'and-utf8-bom-sig-only.txt')]
+        for filetype in (GzipTest, Bz2Test, LzmaTest):
+            if not filetype.open:
+                continue
+            try:
+                tar_name = tmpname + '.' + filetype.suffix
+                out = self.tarfilecmd('-c', tar_name, *files)
+                with filetype.taropen(tar_name) as tar:
+                    tar.getmembers()
+            finally:
+                support.unlink(tar_name)
+
     def test_extract_command(self):
         self.make_simple_tarfile(tmpname)
         for opt in '-e', '--extract':

Misc/NEWS

@@ -13,12 +13,15 @@ Core and Builtins
 Library
 -------
 
+- Issue #23421: Fixed compression in tarfile CLI.  Patch by wdv4758h.
+
 - Issue #23361: Fix possible overflow in Windows subprocess creation code.
 
 - logging.handlers.QueueListener now takes a respect_handler_level keyword
   argument which, if set to True, will pass messages to handlers taking handler
   levels into account.
 
+
 What's New in Python 3.5 alpha 1?
 =================================