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# Copyright The SCons Foundation
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"""Variable type for true/false Variables.
Usage example::
opts = Variables()
opts.Add(BoolVariable('embedded', 'build for an embedded system', False))
env = Environment(variables=opts)
if env['embedded']:
...
"""
from typing import Callable, Tuple, Union
import SCons.Errors
__all__ = ['BoolVariable',]
TRUE_STRINGS = ('y', 'yes', 'true', 't', '1', 'on', 'all')
FALSE_STRINGS = ('n', 'no', 'false', 'f', '0', 'off', 'none')
[docs]
def _text2bool(val: Union[str, bool]) -> bool:
"""Convert boolean-like string to boolean.
If *val* looks like it expresses a bool-like value, based on
the :const:`TRUE_STRINGS` and :const:`FALSE_STRINGS` tuples,
return the appropriate value.
This is usable as a converter function for SCons Variables.
Raises:
ValueError: if *val* cannot be converted to boolean.
"""
if isinstance(val, bool):
# mainly for the subst=False case: default might be a bool
return val
lval = val.lower()
if lval in TRUE_STRINGS:
return True
if lval in FALSE_STRINGS:
return False
# TODO: leave this check to validator?
raise ValueError(f"Invalid value for boolean variable: {val!r}")
[docs]
def _validator(key: str, val, env) -> None:
"""Validate that the value of *key* in *env* is a boolean.
Parameter *val* is not used in the check.
Usable as a validator function for SCons Variables.
Raises:
KeyError: if *key* is not set in *env*
UserError: if the value of *key* is not ``True`` or ``False``.
"""
if env[key] not in (True, False):
msg = f'Invalid value for boolean variable {key!r}: {env[key]}'
raise SCons.Errors.UserError(msg) from None
# lint: W0622: Redefining built-in 'help' (redefined-builtin)
[docs]
def BoolVariable(key, help: str, default) -> Tuple[str, str, str, Callable, Callable]:
"""Return a tuple describing a boolean SCons Variable.
The input parameters describe a boolean variable, using a string
value as described by :const:`TRUE_STRINGS` and :const:`FALSE_STRINGS`.
Returns a tuple including the correct converter and validator.
The *help* text will have ``(yes|no)`` automatically appended to
show the valid values. The result is usable as input to
:meth:`~SCons.Variables.Variables.Add`.
"""
help = f'{help} (yes|no)'
return key, help, default, _validator, _text2bool
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