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