Fix preview mechanism bug (#161)

* Fix bug where PreviewArgumentAction, does not inherit from registered argument action.

* Update test to catch issue. Update fix logic to pass tests.

* python2: in test, use print function from __future__

HISTORY.rst

@@ -3,6 +3,11 @@
 Release History
 ===============
 
+0.6.3
++++++
+* Fix bug where arguments in preview did not call registered actions. This meant that parameter parsing did not behave
+  completely as expected.
+
 0.6.2
 +++++
 * Adds ability to declare that command groups, commands, and arguments are in a preview status and therefore might change or be removed. This is done by passing the kwarg `is_preview=True`.

knack/arguments.py

@@ -162,7 +162,9 @@ def _get_parent_class(self, **kwargs):
         # wrap any existing action
         action = kwargs.get('action', None)
         parent_class = argparse.Action
-        if isinstance(action, argparse.Action):
+
+        # action is either a user-defined Action class or a string referring a library-defined Action
+        if isinstance(action, type) and issubclass(action, argparse.Action):
             parent_class = action
         elif isinstance(action, str):
             parent_class = self.command_loader.cli_ctx.invocation.parser._registries['action'][action]  # pylint: disable=protected-access

setup.py

@@ -9,7 +9,7 @@
 from codecs import open
 from setuptools import setup, find_packages
 
-VERSION = '0.6.2'
+VERSION = '0.6.3'
 
 DEPENDENCIES = [
     'argcomplete',

tests/test_preview.py

@@ -3,17 +3,19 @@
 # Licensed under the MIT License. See License.txt in the project root for license information.
 # --------------------------------------------------------------------------------------------
 
-from __future__ import unicode_literals
+from __future__ import unicode_literals, print_function
 
 import unittest
 try:
     import mock
 except ImportError:
     from unittest import mock
-from threading import Lock
+
+import sys
+import argparse
 
 from knack.arguments import ArgumentsContext
-from knack.commands import CLICommand, CLICommandsLoader, CommandGroup
+from knack.commands import CLICommandsLoader, CommandGroup
 
 from tests.util import DummyCLI, redirect_io
 
@@ -148,9 +150,13 @@ def test_preview_command_implicitly(self):
 class TestArgumentPreview(unittest.TestCase):
 
     def setUp(self):
-
         from knack.help_files import helps
 
+        class LoggerAction(argparse.Action):
+
+            def __call__(self, parser, namespace, values, option_string=None):
+                print("Side-effect from some original action!", file=sys.stderr)
+
         class PreviewTestCommandLoader(CLICommandsLoader):
             def load_command_table(self, args):
                 super(PreviewTestCommandLoader, self).load_command_table(args)
@@ -160,7 +166,7 @@ def load_command_table(self, args):
 
             def load_arguments(self, command):
                 with ArgumentsContext(self, 'arg-test') as c:
-                    c.argument('arg1', help='Arg1', is_preview=True)
+                    c.argument('arg1', help='Arg1', is_preview=True, action=LoggerAction)
 
                 super(PreviewTestCommandLoader, self).load_arguments(command)
 
@@ -188,8 +194,11 @@ def test_preview_arguments_execute(self):
         """ Ensure deprecated arguments can be used. """
         self.cli_ctx.invoke('arg-test --arg1 foo --opt1 bar'.split())
         actual = self.io.getvalue()
-        expected = "Argument '--arg1' is in preview. It may be changed/removed in a future release."
-        self.assertIn(expected, actual)
+        preview_expected = "Argument '--arg1' is in preview. It may be changed/removed in a future release."
+        self.assertIn(preview_expected, actual)
+
+        action_expected = "Side-effect from some original action!"
+        self.assertIn(action_expected, actual)
 
 
 if __name__ == '__main__':