fix handling of --

Author: picnixz

Lib/test/test_timeit.py

@@ -246,9 +246,11 @@ def run_main(self, seconds_per_increment=1.0, switches=None, timer=None):
         args.append(self.fake_stmt)
         # timeit.main() modifies sys.path, so save and restore it.
         orig_sys_path = sys.path[:]
-        with captured_stdout() as s:
-            timeit.main(args=args, _wrap_timer=timer.wrap_timer)
-        sys.path[:] = orig_sys_path[:]
+        try:
+            with captured_stdout() as s:
+                timeit.main(args=args, _wrap_timer=timer.wrap_timer)
+        finally:
+            sys.path[:] = orig_sys_path[:]
         return s.getvalue()
 
     def test_main_bad_switch(self):
@@ -353,6 +355,17 @@ def test_main_exception_fixed_reps(self):
             s = self.run_main(switches=['-n1', '1/0'])
         self.assert_exc_string(error_stringio.getvalue(), 'ZeroDivisionError')
 
+    def test_main_without_option_separator(self):
+        out = self.run_main(switches=['-n2', '-r2', '1'])
+        self.assertEqual(out, "2 loops, best of 2: 1 sec per loop\n")
+
+    def test_main_with_option_separator(self):
+        with self.assertRaises(SyntaxError):
+            self.run_main(switches=['--', '1 + 1', '--'])
+
+        out = self.run_main(switches=['-n2', '-r2', '--', '1'])
+        self.assertEqual(out, "2 loops, best of 2: 1 sec per loop\n")
+
     def test_main_with_option_like_at_the_end(self):
         with captured_stderr() as s:
             self.run_main(switches=['-n1', '1 + 1', '-n1'])

Lib/timeit.py

@@ -227,6 +227,9 @@ def _make_parser():
 argument in quotes and using leading spaces.  Multiple -s options are
 treated similarly.
 
+Use "--" to separate command-line options from actual statements,
+or when a statement starts with '-'.
+
 If -n is not given, a suitable number of loops is calculated by trying
 increasing numbers from the sequence 1, 2, 5, 10, 20, 50, ... until the
 total time is at least 0.2 seconds.
@@ -265,13 +268,9 @@ def _make_parser():
         "-v", "--verbose", action="count", default=0,
         help="print raw timing results; repeat for more digits precision",
     )
-    # add a dummy option to document '--'
-    group.add_argument(
-        "--", dest="_", action="store_const", const=None,
-        help="separate options from statement; "
-             "use when statement starts with -",
-    )
-    # use argparse.REMAINDER to ignore option-like argument found at the end
+    # Use argparse.REMAINDER to ignore option-like argument found at the end.
+    # If '--' is being specified as the "first" statement, it will be ignored
+    # and used to separate the options from the list of statements.
     group.add_argument(
         "statement", nargs=argparse.REMAINDER,
         help="statement to be timed (default: 'pass')",
@@ -300,6 +299,8 @@ def main(args=None, *, _wrap_timer=None):
     args = parser.parse_args(args)
 
     setup = "\n".join(args.setup) or "pass"
+    if args.statement and args.statement[0] == '--':
+        args.statement.pop(0)
     stmt = "\n".join(args.statement) or "pass"
     timer = time.process_time if args.process else default_timer
     number = args.number  # will be deduced if 0