|
|
|
|
|
""" |
|
Commonly useful converters. |
|
""" |
|
|
|
|
|
import typing |
|
|
|
from ._compat import _AnnotationExtractor |
|
from ._make import NOTHING, Factory, pipe |
|
|
|
|
|
__all__ = [ |
|
"default_if_none", |
|
"optional", |
|
"pipe", |
|
"to_bool", |
|
] |
|
|
|
|
|
def optional(converter): |
|
""" |
|
A converter that allows an attribute to be optional. An optional attribute |
|
is one which can be set to ``None``. |
|
|
|
Type annotations will be inferred from the wrapped converter's, if it |
|
has any. |
|
|
|
:param callable converter: the converter that is used for non-``None`` |
|
values. |
|
|
|
.. versionadded:: 17.1.0 |
|
""" |
|
|
|
def optional_converter(val): |
|
if val is None: |
|
return None |
|
return converter(val) |
|
|
|
xtr = _AnnotationExtractor(converter) |
|
|
|
t = xtr.get_first_param_type() |
|
if t: |
|
optional_converter.__annotations__["val"] = typing.Optional[t] |
|
|
|
rt = xtr.get_return_type() |
|
if rt: |
|
optional_converter.__annotations__["return"] = typing.Optional[rt] |
|
|
|
return optional_converter |
|
|
|
|
|
def default_if_none(default=NOTHING, factory=None): |
|
""" |
|
A converter that allows to replace ``None`` values by *default* or the |
|
result of *factory*. |
|
|
|
:param default: Value to be used if ``None`` is passed. Passing an instance |
|
of `attrs.Factory` is supported, however the ``takes_self`` option |
|
is *not*. |
|
:param callable factory: A callable that takes no parameters whose result |
|
is used if ``None`` is passed. |
|
|
|
:raises TypeError: If **neither** *default* or *factory* is passed. |
|
:raises TypeError: If **both** *default* and *factory* are passed. |
|
:raises ValueError: If an instance of `attrs.Factory` is passed with |
|
``takes_self=True``. |
|
|
|
.. versionadded:: 18.2.0 |
|
""" |
|
if default is NOTHING and factory is None: |
|
msg = "Must pass either `default` or `factory`." |
|
raise TypeError(msg) |
|
|
|
if default is not NOTHING and factory is not None: |
|
msg = "Must pass either `default` or `factory` but not both." |
|
raise TypeError(msg) |
|
|
|
if factory is not None: |
|
default = Factory(factory) |
|
|
|
if isinstance(default, Factory): |
|
if default.takes_self: |
|
msg = "`takes_self` is not supported by default_if_none." |
|
raise ValueError(msg) |
|
|
|
def default_if_none_converter(val): |
|
if val is not None: |
|
return val |
|
|
|
return default.factory() |
|
|
|
else: |
|
|
|
def default_if_none_converter(val): |
|
if val is not None: |
|
return val |
|
|
|
return default |
|
|
|
return default_if_none_converter |
|
|
|
|
|
def to_bool(val): |
|
""" |
|
Convert "boolean" strings (e.g., from env. vars.) to real booleans. |
|
|
|
Values mapping to :code:`True`: |
|
|
|
- :code:`True` |
|
- :code:`"true"` / :code:`"t"` |
|
- :code:`"yes"` / :code:`"y"` |
|
- :code:`"on"` |
|
- :code:`"1"` |
|
- :code:`1` |
|
|
|
Values mapping to :code:`False`: |
|
|
|
- :code:`False` |
|
- :code:`"false"` / :code:`"f"` |
|
- :code:`"no"` / :code:`"n"` |
|
- :code:`"off"` |
|
- :code:`"0"` |
|
- :code:`0` |
|
|
|
:raises ValueError: for any other value. |
|
|
|
.. versionadded:: 21.3.0 |
|
""" |
|
if isinstance(val, str): |
|
val = val.lower() |
|
truthy = {True, "true", "t", "yes", "y", "on", "1", 1} |
|
falsy = {False, "false", "f", "no", "n", "off", "0", 0} |
|
try: |
|
if val in truthy: |
|
return True |
|
if val in falsy: |
|
return False |
|
except TypeError: |
|
|
|
pass |
|
msg = f"Cannot convert value to bool: {val}" |
|
raise ValueError(msg) |
|
|
