Make sure the the viewer scripts exits with the correct error code when displaying the help page

Lauszus · Lauszus · commit 6f5d6f26992e · 2018-09-24T20:50:15.000+02:00
Fixes #427
diff --git a/can/viewer.py b/can/viewer.py
@@ -384,7 +384,7 @@ def parse_args(args):
                           choices=sorted(can.VALID_INTERFACES))
 
     # Print help message when no arguments are given
-    if len(args) < 2:
+    if len(args) == 0:
         parser.print_help(sys.stderr)
         import errno
         raise SystemExit(errno.EINVAL)
diff --git a/test/test_viewer.py b/test/test_viewer.py
@@ -436,9 +436,16 @@ def test_parse_args(self):
         parsed_args, _, _ = parse_args(['--interface', 'pcan'])
         self.assertEqual(parsed_args.interface, 'pcan')
 
-        # Make sure the help message is printed when no arguments are given
-        with self.assertRaises(SystemExit):
-            parsed_args, _, _ = parse_args([])
+        # Make sure the it exits with the correct error code when displaying the help page
+        # See: https://github.com/hardbyte/python-can/issues/427
+        with self.assertRaises(SystemExit) as cm:
+            parse_args(['-h'])
+        self.assertEqual(cm.exception.code, 0)
+
+        with self.assertRaises(SystemExit) as cm:
+            parse_args([])
+        import errno
+        self.assertEqual(cm.exception.code, errno.EINVAL)
 
 
 if __name__ == '__main__':
