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| #!/usr/bin/env python3 | |
| # Copyright (c) Facebook, Inc. and its affiliates. | |
| # All rights reserved. | |
| # | |
| # This source code is licensed under the BSD-style license found in the | |
| # LICENSE file in the root directory of this source tree. | |
| import os | |
| from argparse import Action | |
| class env(Action): | |
| """ | |
| Get argument values from ``PET_{dest}`` before defaulting to the given ``default`` value. | |
| For flags (e.g. ``--standalone``) | |
| use ``check_env`` instead. | |
| .. note:: when multiple option strings are specified, ``dest`` is | |
| the longest option string (e.g. for ``"-f", "--foo"`` | |
| the env var to set is ``PET_FOO`` not ``PET_F``) | |
| Example: | |
| :: | |
| parser.add_argument("-f", "--foo", action=env, default="bar") | |
| ./program -> args.foo="bar" | |
| ./program -f baz -> args.foo="baz" | |
| ./program --foo baz -> args.foo="baz" | |
| PET_FOO="env_bar" ./program -f baz -> args.foo="baz" | |
| PET_FOO="env_bar" ./program --foo baz -> args.foo="baz" | |
| PET_FOO="env_bar" ./program -> args.foo="env_bar" | |
| parser.add_argument("-f", "--foo", action=env, required=True) | |
| ./program -> fails | |
| ./program -f baz -> args.foo="baz" | |
| PET_FOO="env_bar" ./program -> args.foo="env_bar" | |
| PET_FOO="env_bar" ./program -f baz -> args.foo="baz" | |
| """ | |
| def __init__(self, dest, default=None, required=False, **kwargs) -> None: | |
| env_name = f"PET_{dest.upper()}" | |
| default = os.environ.get(env_name, default) | |
| # ``required`` means that it NEEDS to be present in the command-line args | |
| # rather than "this option requires a value (either set explicitly or default" | |
| # so if we found default then we don't "require" it to be in the command-line | |
| # so set it to False | |
| if default: | |
| required = False | |
| super().__init__(dest=dest, default=default, required=required, **kwargs) | |
| def __call__(self, parser, namespace, values, option_string=None): | |
| setattr(namespace, self.dest, values) | |
| class check_env(Action): | |
| """ | |
| Check whether the env var ``PET_{dest}`` exists before defaulting to the given ``default`` value. | |
| Equivalent to | |
| ``store_true`` argparse built-in action except that the argument can | |
| be omitted from the commandline if the env var is present and has a | |
| non-zero value. | |
| .. note:: it is redundant to pass ``default=True`` for arguments | |
| that use this action because a flag should be ``True`` | |
| when present and ``False`` otherwise. | |
| Example: | |
| :: | |
| parser.add_argument("--verbose", action=check_env) | |
| ./program -> args.verbose=False | |
| ./program --verbose -> args.verbose=True | |
| PET_VERBOSE=1 ./program -> args.verbose=True | |
| PET_VERBOSE=0 ./program -> args.verbose=False | |
| PET_VERBOSE=0 ./program --verbose -> args.verbose=True | |
| Anti-pattern (don't do this): | |
| :: | |
| parser.add_argument("--verbose", action=check_env, default=True) | |
| ./program -> args.verbose=True | |
| ./program --verbose -> args.verbose=True | |
| PET_VERBOSE=1 ./program -> args.verbose=True | |
| PET_VERBOSE=0 ./program -> args.verbose=False | |
| """ | |
| def __init__(self, dest, default=False, **kwargs) -> None: | |
| env_name = f"PET_{dest.upper()}" | |
| default = bool(int(os.environ.get(env_name, "1" if default else "0"))) | |
| super().__init__(dest=dest, const=True, default=default, nargs=0, **kwargs) | |
| def __call__(self, parser, namespace, values, option_string=None): | |
| setattr(namespace, self.dest, self.const) | |