view mercurial/thirdparty/attr/validators.py @ 36160:9fd8c2a3db5a

narrowspec: move module into core

Having support for parsing the narrow specification in core is
necessary for moving many other parts of narrow to core.

We do still want to harmonize the narrow spec with the sparse
spec. And the format needs to be documented. But this shouldn't
hold up the code moving to core.

Differential Revision: https://phab.mercurial-scm.org/D2201

"""
Commonly useful validators.
"""

from __future__ import absolute_import, division, print_function

from ._make import attr, attributes, and_, _AndValidator


__all__ = [
    "and_",
    "in_",
    "instance_of",
    "optional",
    "provides",
]


@attributes(repr=False, slots=True, hash=True)
class _InstanceOfValidator(object):
    type = attr()

    def __call__(self, inst, attr, value):
        """
        We use a callable class to be able to change the ``__repr__``.
        """
        if not isinstance(value, self.type):
            raise TypeError(
                "'{name}' must be {type!r} (got {value!r} that is a "
                "{actual!r})."
                .format(name=attr.name, type=self.type,
                        actual=value.__class__, value=value),
                attr, self.type, value,
            )

    def __repr__(self):
        return (
            "<instance_of validator for type {type!r}>"
            .format(type=self.type)
        )


def instance_of(type):
    """
    A validator that raises a :exc:`TypeError` if the initializer is called
    with a wrong type for this particular attribute (checks are perfomed using
    :func:`isinstance` therefore it's also valid to pass a tuple of types).

    :param type: The type to check for.
    :type type: type or tuple of types

    :raises TypeError: With a human readable error message, the attribute
        (of type :class:`attr.Attribute`), the expected type, and the value it
        got.
    """
    return _InstanceOfValidator(type)


@attributes(repr=False, slots=True, hash=True)
class _ProvidesValidator(object):
    interface = attr()

    def __call__(self, inst, attr, value):
        """
        We use a callable class to be able to change the ``__repr__``.
        """
        if not self.interface.providedBy(value):
            raise TypeError(
                "'{name}' must provide {interface!r} which {value!r} "
                "doesn't."
                .format(name=attr.name, interface=self.interface, value=value),
                attr, self.interface, value,
            )

    def __repr__(self):
        return (
            "<provides validator for interface {interface!r}>"
            .format(interface=self.interface)
        )


def provides(interface):
    """
    A validator that raises a :exc:`TypeError` if the initializer is called
    with an object that does not provide the requested *interface* (checks are
    performed using ``interface.providedBy(value)`` (see `zope.interface
    <https://zopeinterface.readthedocs.io/en/latest/>`_).

    :param zope.interface.Interface interface: The interface to check for.

    :raises TypeError: With a human readable error message, the attribute
        (of type :class:`attr.Attribute`), the expected interface, and the
        value it got.
    """
    return _ProvidesValidator(interface)


@attributes(repr=False, slots=True, hash=True)
class _OptionalValidator(object):
    validator = attr()

    def __call__(self, inst, attr, value):
        if value is None:
            return

        self.validator(inst, attr, value)

    def __repr__(self):
        return (
            "<optional validator for {what} or None>"
            .format(what=repr(self.validator))
        )


def optional(validator):
    """
    A validator that makes an attribute optional.  An optional attribute is one
    which can be set to ``None`` in addition to satisfying the requirements of
    the sub-validator.

    :param validator: A validator (or a list of validators) that is used for
        non-``None`` values.
    :type validator: callable or :class:`list` of callables.

    .. versionadded:: 15.1.0
    .. versionchanged:: 17.1.0 *validator* can be a list of validators.
    """
    if isinstance(validator, list):
        return _OptionalValidator(_AndValidator(validator))
    return _OptionalValidator(validator)


@attributes(repr=False, slots=True, hash=True)
class _InValidator(object):
    options = attr()

    def __call__(self, inst, attr, value):
        if value not in self.options:
            raise ValueError(
                "'{name}' must be in {options!r} (got {value!r})"
                .format(name=attr.name, options=self.options, value=value)
            )

    def __repr__(self):
        return (
            "<in_ validator with options {options!r}>"
            .format(options=self.options)
        )


def in_(options):
    """
    A validator that raises a :exc:`ValueError` if the initializer is called
    with a value that does not belong in the options provided.  The check is
    performed using ``value in options``.

    :param options: Allowed options.
    :type options: list, tuple, :class:`enum.Enum`, ...

    :raises ValueError: With a human readable error message, the attribute (of
       type :class:`attr.Attribute`), the expected options, and the value it
       got.

    .. versionadded:: 17.1.0
    """
    return _InValidator(options)