Command suggestion feature from CLI 2.0

HISTORY.rst

@@ -7,6 +7,7 @@ Release History
 +++++
 * 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`.
 * Adds a generic `TagDecorator` class to `knack.util` that allows you to create your own colorized tags like `[Preview]` and `[Deprecated]`.
+* When an incorrect command name is entered, Knack will now attempt to suggest the closest alternative.
 
 0.6.1
 +++++

knack/parser.py

@@ -3,6 +3,8 @@
 # Licensed under the MIT License. See License.txt in the project root for license information.
 # --------------------------------------------------------------------------------------------
 
+from __future__ import print_function
+
 import argparse
 
 from .deprecation import Deprecated
@@ -255,3 +257,27 @@ def parse_args(self, args=None, namespace=None):
         """
         self._expand_prefixed_files(args)
         return super(CLICommandParser, self).parse_args(args)
+
+    def _check_value(self, action, value):
+        # Override to customize the error message when a argument is not among the available choices
+        # converted value must be one of the choices (if specified)
+        import difflib
+        import sys
+
+        if action.choices is not None and value not in action.choices:
+            # parser has no `command_source`, value is part of command itself
+            error_msg = "{prog}: '{value}' is not in the '{prog}' command group. See '{prog} --help'.".format(
+                prog=self.prog, value=value)
+            logger.error(error_msg)
+            candidates = difflib.get_close_matches(value, action.choices, cutoff=0.7)
+            if candidates:
+                print_args = {
+                    's': 's' if len(candidates) > 1 else '',
+                    'verb': 'are' if len(candidates) > 1 else 'is',
+                    'value': value
+                }
+                suggestion_msg = "\nThe most similar choice{s} to '{value}' {verb}:\n".format(**print_args)
+                suggestion_msg += '\n'.join(['\t' + candidate for candidate in candidates])
+                print(suggestion_msg, file=sys.stderr)
+
+            self.exit(2)

tests/test_cli_scenarios.py

@@ -4,14 +4,14 @@
 # --------------------------------------------------------------------------------------------
 
 import os
+from collections import OrderedDict
 import unittest
 try:
     import mock
 except ImportError:
     from unittest import mock
 import mock
 
-from collections import OrderedDict
 from six import StringIO
 
 from knack import CLI

tests/test_command_with_configured_defaults.py

@@ -5,17 +5,15 @@
 from __future__ import print_function
 import os
 import logging
+import sys
 import unittest
 try:
     import mock
 except ImportError:
     from unittest import mock
-from six import StringIO
-import sys
 
 from knack.arguments import ArgumentsContext
-from knack.commands import CLICommandsLoader, CLICommand, CommandGroup
-from knack.config import CLIConfig
+from knack.commands import CLICommandsLoader, CommandGroup
 from tests.util import DummyCLI, redirect_io
 
 

tests/test_deprecation.py

@@ -28,6 +28,7 @@ def example_arg_handler(arg1, opt1, arg2=None, opt2=None, arg3=None,
     pass
 
 
+# pylint: disable=line-too-long
 class TestCommandDeprecation(unittest.TestCase):
 
     def setUp(self):
@@ -132,7 +133,8 @@ def test_deprecate_command_expired_execute(self):
         with self.assertRaises(SystemExit):
             self.cli_ctx.invoke('cmd5 -h'.split())
         actual = self.io.getvalue()
-        self.assertTrue(u'invalid choice' in actual and u'cmd5' in actual)
+        expected = """The most similar choices to 'cmd5'"""
+        self.assertIn(expected, actual)
 
 
 class TestCommandGroupDeprecation(unittest.TestCase):
@@ -231,7 +233,8 @@ def test_deprecate_command_group_expired(self):
         with self.assertRaises(SystemExit):
             self.cli_ctx.invoke('group5 -h'.split())
         actual = self.io.getvalue()
-        self.assertTrue(u'invalid choice' in actual and u'group5' in actual)
+        expected = """The most similar choices to 'group5'"""
+        self.assertIn(expected, actual)
 
     @redirect_io
     def test_deprecate_command_implicitly(self):

tests/test_introspection.py

@@ -3,12 +3,7 @@
 # Licensed under the MIT License. See License.txt in the project root for license information.
 # --------------------------------------------------------------------------------------------
 
-import os
-import stat
 import unittest
-import tempfile
-import mock
-from six.moves import configparser
 
 from knack.introspection import extract_full_summary_from_signature, option_descriptions, extract_args_from_signature