cosalib/cli.py: Cli/BuildCli class for reusability

Cli:
- Base class which can be used by other Cli classes
- Sets up the logger
- Provides an environment variable driven argument method
- Appends env variables to env args help text

BuildCli:
- Provides common arguments for build commands

Code:
from cosalib.cli import BuildCli

b = BuildCli(usage='test')
b.add_argument('-t', '--test', help='test')
b.add_argument('-e', '--env-test', env_var='ENV_VAR', default='default')
print(b.parse_args())
b.print_help()

Output:
usage: test

optional arguments:
  -h, --help            show this help message and exit
  --log-level {CRITICAL,FATAL,ERROR,WARN,WARNING,INFO,DEBUG,NOTSET}
                        Set the log level (Env: COSA_LOG_LEVEL)
  --build BUILD         Override build id, defaults to latest
  --buildroot BUILDROOT
                        Build diretory
  --dump                Dump the manfiest and exit
  -t TEST, --test TEST  test
  -e ENV_TEST, --env-test ENV_TEST
                        (Env: ENV_VAR)

Signed-off-by: Steve Milner <smilner@redhat.com>

src/cosalib/cli.py

@@ -0,0 +1,93 @@
+# NOTE: PYTHONUNBUFFERED is set in cmdlib.sh for unbuffered output
+# pylint: disable=C0103
+
+import argparse
+import logging as log
+import os
+
+
+class Cli(argparse.ArgumentParser):
+    """
+    Abstraction for executing commands from the cli.
+    """
+
+    def __init__(self, *args, **kwargs):
+        """
+        Initializes the Cli instance.
+
+        :param kwargs: All keyword arguments which will pass to ArgumentParser
+        :type kwargs: dict
+        """
+        argparse.ArgumentParser.__init__(self, *args, **kwargs)
+        self.add_argument(
+            '--log-level', env_var='COSA_LOG_LEVEL', default='info',
+            choices=log._nameToLevel.keys(), help='Set the log level')
+
+    def add_argument(self, *args, **kwargs):
+        """
+        Overloads the add_argument to be able to also read from
+        the environment. To read from the environment provide
+        the keyword arugment env_var.
+
+        :param args: Non keyword arguments to pass to add_argument
+        :type args: list
+        :param kwargs: Keyword arguments to pass to add_argument
+        :type kwargs: dict
+        """
+        env_var = kwargs.pop('env_var', None)
+        if env_var is not None:
+            if kwargs.get('help') is None:
+                kwargs['help'] = ''
+            kwargs['help'] = kwargs['help'] + ' (Env: {})'.format(env_var)
+            default = kwargs.pop('default', None)
+            super().add_argument(
+                *args, default=os.environ.get(env_var, default), **kwargs)
+        else:
+            super().add_argument(*args, **kwargs)
+
+    def parse_args(self):
+        """
+        Parses the arguments passed in, verifies inputs, sets the logger,
+        and returns the arguments.
+
+        :returns: The parsed arguments
+        :rtype: argparse.Namepsace
+        """
+        args = super().parse_args()
+        self._set_logger(args.log_level)
+        return args
+
+    def _set_logger(self, level):
+        """
+        Set the log level
+
+        :param level: set the log level
+        :type level: str
+        """
+        log.basicConfig(
+            format='[%(asctime)s  %(levelname)s]: %(message)s',
+            level=log._nameToLevel.get(level.upper(), log.DEBUG))
+
+
+class BuildCli(Cli):
+    """
+    Cli class that adds in reusable build specific arguments.
+    """
+
+    def __init__(self, *args, **kwargs):
+        """
+        Initializes the BuildCli instance.
+
+        :param kwargs: All keyword arguments which will pass to ArgumentParser
+        :type kwargs: dict
+        """
+        Cli.__init__(self, *args, **kwargs)
+        # Set common arguments
+        self.add_argument(
+            '--build', default='latest',
+            help='Override build id, defaults to latest')
+        self.add_argument(
+            '--buildroot', default='builds', help='Build diretory')
+        self.add_argument(
+            '--dump', default=False, action='store_true',
+            help='Dump the manfiest and exit')