add cloud-init main

This is start of the cloud-init main executable.

Change-Id: I795e1d279a99476fb6cd33d1e7ad6a7af0978c8d

cloudinit/shell.py

@@ -3,10 +3,117 @@
 #
 # vi: ts=4 expandtab
 
+import argparse
+import sys
 
-def main():
+
-    print("Run cloudinit run!")
+def populate_parser(parser, common, subcommands):
+    """Populate an ArgumentParser with data rather than code
+
+    This replaces boilerplate code with boilerplate data when populating a
+    :py:class:`argparse.ArgumentParser`
+
+    :param parser:
+        the :py:mod:`argparse.ArgumentParser` to populate.
+
+    :param common:
+        a :py:func:`list` of tuples.  Each tuple is args and kwargs that are
+        passed onto :py:func:`argparse.ArgumentParser.add_argument`
+
+    :param subcommands:
+        a :py:func:dict of subcommands to add.
+        The key is added as the subcommand name.
+        'func' is called to implement the subcommand.
+        'help' is set up as the subcommands help message
+        entries in 'opts' are passed onto
+        :py:func:`argparse.ArgumentParser.add_argument`
+    """
+    for (args, kwargs) in common:
+        parser.add_argument(*args, **kwargs)
+
+    subparsers = parser.add_subparsers()
+    for subcmd in sorted(subcommands):
+        val = subcommands[subcmd]
+        sparser = subparsers.add_parser(subcmd, help=val['help'])
+        sparser.set_defaults(func=val['func'], name=subcmd)
+        for (args, kwargs) in val.get('opts', {}):
+            sparser.add_argument(*args, **kwargs)
+
+
+def main(args=sys.argv):
+    parser = argparse.ArgumentParser(prog='cloud-init')
+
+    populate_parser(parser, COMMON_ARGS, SUBCOMMANDS)
+    parsed = parser.parse_args(args[1:])
+
+    parsed.func(parsed)
+    return 0
+
+
+def main_version(args):
+    sys.stdout.write("cloud-init 1.9\n")
+    return
+
+
+def unimplemented_subcommand(args):
+    raise NotImplementedError(
+        "sub command '{0}' is not implemented".format(args.name))
+
+
+COMMON_ARGS = [
+    (('--verbose', '-v'), {'action': 'count', 'default': 0}),
+]
+
+SUBCOMMANDS = {
+    # The stages a normal boot takes
+    'network': {
+        'func': unimplemented_subcommand,
+        'help': 'locate and apply networking configuration',
+    },
+    'search': {
+        'func': unimplemented_subcommand,
+        'help': 'search available data sources',
+    },
+    'config': {
+        'func': unimplemented_subcommand,
+        'help': 'run available config modules',
+    },
+    'config-final': {
+        'func': unimplemented_subcommand,
+        'help': 'run "final" config modules',
+    },
+    # utility
+    'version': {
+        'func': main_version,
+        'help': 'print cloud-init version',
+    },
+    'all': {
+        'func': unimplemented_subcommand,
+        'help': 'run all stages as if from boot',
+        'opts': [
+            (('--clean',),
+             {'help': 'clear any prior system state',
+              'action': 'store_true', 'default': False})],
+    },
+    'clean': {
+        'func': unimplemented_subcommand,
+        'help': 'clear any prior system state.',
+        'opts': [
+            (('-F', '--full'),
+             {'help': 'be more complete (remove logs).',
+              'default': False, 'action': 'store_true'}),
+        ],
+    },
+    'query': {
+        'func': unimplemented_subcommand,
+        'help': 'query system state',
+        'opts': [
+            (('--json',),
+             {'help': 'output in json format',
+              'action': 'store_true', 'default': False})]
+    },
+}
 
 
 if __name__ == '__main__':
-    main()
+    sys.exit(main())

cloudinit/tests/test_shell.py

@@ -0,0 +1,31 @@
+# Copyright 2015 Canonical Ltd.
+# This file is part of cloud-init.  See LICENCE file for license information.
+#
+# vi: ts=4 expandtab
+
+import cloudinit.shell as shell
+
+from cloudinit.tests import TestCase
+from cloudinit.tests.util import mock
+
+
+class TestMain(TestCase):
+
+    def test_help_exits_success(self):
+        with mock.patch('cloudinit.shell.sys.stdout'):
+            exc = self.assertRaises(
+                SystemExit, shell.main, args=['cloud-init', '--help'])
+            self.assertEqual(exc.code, 0)
+
+    def test_invalid_arguments_exit_fail(self):
+        # silence writes that get to stderr
+        with mock.patch('cloudinit.shell.sys.stderr'):
+            exc = self.assertRaises(
+                SystemExit, shell.main, args=['cloud-init', 'bogus_argument'])
+            self.assertNotEqual(exc.code, 0)
+
+    @mock.patch('cloudinit.shell.sys.stdout')
+    def test_version_shows_cloud_init(self, mock_out_write):
+        shell.main(args=['cloud-init', 'version'])
+        write_arg = mock_out_write.write.call_args[0][0]
+        self.assertTrue(write_arg.startswith('cloud-init'))