validators.py

# SPDX-License-Identifier: MIT

"""
Commonly useful validators.
"""

from __future__ import absolute_import, division, print_function

import operator
import re

from contextlib import contextmanager

from ._config import get_run_validators, set_run_validators
from ._make import _AndValidator, and_, attrib, attrs
from .exceptions import NotCallableError


try:
    Pattern = re.Pattern
except AttributeError:  # Python <3.7 lacks a Pattern type.
    Pattern = type(re.compile(""))


__all__ = [
    "and_",
    "deep_iterable",
    "deep_mapping",
    "disabled",
    "ge",
    "get_disabled",
    "gt",
    "in_",
    "instance_of",
    "is_callable",
    "le",
    "lt",
    "matches_re",
    "max_len",
    "optional",
    "provides",
    "set_disabled",
]


def set_disabled(disabled):
    """
    Globally disable or enable running validators.

    By default, they are run.

    :param disabled: If ``True``, disable running all validators.
    :type disabled: bool

    .. warning::

        This function is not thread-safe!

    .. versionadded:: 21.3.0
    """
    set_run_validators(not disabled)


def get_disabled():
    """
    Return a bool indicating whether validators are currently disabled or not.

    :return: ``True`` if validators are currently disabled.
    :rtype: bool

    .. versionadded:: 21.3.0
    """
    return not get_run_validators()


@contextmanager
def disabled():
    """
    Context manager that disables running validators within its context.

    .. warning::

        This context manager is not thread-safe!

    .. versionadded:: 21.3.0
    """
    set_run_validators(False)
    try:
        yield
    finally:
        set_run_validators(True)


@attrs(repr=False, slots=True, hash=True)
class _InstanceOfValidator(object):
    type = attrib()

    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 `TypeError` if the initializer is called
    with a wrong type for this particular attribute (checks are performed using
    `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 `attrs.Attribute`), the expected type, and the value it
        got.
    """
    return _InstanceOfValidator(type)


@attrs(repr=False, frozen=True, slots=True)
class _MatchesReValidator(object):
    pattern = attrib()
    match_func = attrib()

    def __call__(self, inst, attr, value):
        """
        We use a callable class to be able to change the ``__repr__``.
        """
        if not self.match_func(value):
            raise ValueError(
                "'{name}' must match regex {pattern!r}"
                " ({value!r} doesn't)".format(
                    name=attr.name, pattern=self.pattern.pattern, value=value
                ),
                attr,
                self.pattern,
                value,
            )

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


def matches_re(regex, flags=0, func=None):
    r"""
    A validator that raises `ValueError` if the initializer is called
    with a string that doesn't match *regex*.

    :param regex: a regex string or precompiled pattern to match against
    :param int flags: flags that will be passed to the underlying re function
        (default 0)
    :param callable func: which underlying `re` function to call (options
        are `re.fullmatch`, `re.search`, `re.match`, default
        is ``None`` which means either `re.fullmatch` or an emulation of
        it on Python 2). For performance reasons, they won't be used directly
        but on a pre-`re.compile`\ ed pattern.

    .. versionadded:: 19.2.0
    .. versionchanged:: 21.3.0 *regex* can be a pre-compiled pattern.
    """
    fullmatch = getattr(re, "fullmatch", None)
    valid_funcs = (fullmatch, None, re.search, re.match)
    if func not in valid_funcs:
        raise ValueError(
            "'func' must be one of {}.".format(
                ", ".join(
                    sorted(
                        e and e.__name__ or "None" for e in set(valid_funcs)
                    )
                )
            )
        )

    if isinstance(regex, Pattern):
        if flags:
            raise TypeError(
                "'flags' can only be used with a string pattern; "
                "pass flags to re.compile() instead"
            )
        pattern = regex
    else:
        pattern = re.compile(regex, flags)

    if func is re.match:
        match_func = pattern.match
    elif func is re.search:
        match_func = pattern.search
    elif fullmatch:
        match_func = pattern.fullmatch
    else:  # Python 2 fullmatch emulation (https://bugs.python.org/issue16203)
        pattern = re.compile(
            r"(?:{})\Z".format(pattern.pattern), pattern.flags
        )
        match_func = pattern.match

    return _MatchesReValidator(pattern, match_func)


@attrs(repr=False, slots=True, hash=True)
class _ProvidesValidator(object):
    interface = attrib()

    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 `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 interface: The interface to check for.
    :type interface: ``zope.interface.Interface``

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


@attrs(repr=False, slots=True, hash=True)
class _OptionalValidator(object):
    validator = attrib()

    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 `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)


@attrs(repr=False, slots=True, hash=True)
class _InValidator(object):
    options = attrib()

    def __call__(self, inst, attr, value):
        try:
            in_options = value in self.options
        except TypeError:  # e.g. `1 in "abc"`
            in_options = False

        if not in_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 `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, `enum.Enum`, ...

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

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


@attrs(repr=False, slots=False, hash=True)
class _IsCallableValidator(object):
    def __call__(self, inst, attr, value):
        """
        We use a callable class to be able to change the ``__repr__``.
        """
        if not callable(value):
            message = (
                "'{name}' must be callable "
                "(got {value!r} that is a {actual!r})."
            )
            raise NotCallableError(
                msg=message.format(
                    name=attr.name, value=value, actual=value.__class__
                ),
                value=value,
            )

    def __repr__(self):
        return "<is_callable validator>"


def is_callable():
    """
    A validator that raises a `attr.exceptions.NotCallableError` if the
    initializer is called with a value for this particular attribute
    that is not callable.

    .. versionadded:: 19.1.0

    :raises `attr.exceptions.NotCallableError`: With a human readable error
        message containing the attribute (`attrs.Attribute`) name,
        and the value it got.
    """
    return _IsCallableValidator()


@attrs(repr=False, slots=True, hash=True)
class _DeepIterable(object):
    member_validator = attrib(validator=is_callable())
    iterable_validator = attrib(
        default=None, validator=optional(is_callable())
    )

    def __call__(self, inst, attr, value):
        """
        We use a callable class to be able to change the ``__repr__``.
        """
        if self.iterable_validator is not None:
            self.iterable_validator(inst, attr, value)

        for member in value:
            self.member_validator(inst, attr, member)

    def __repr__(self):
        iterable_identifier = (
            ""
            if self.iterable_validator is None
            else " {iterable!r}".format(iterable=self.iterable_validator)
        )
        return (
            "<deep_iterable validator for{iterable_identifier}"
            " iterables of {member!r}>"
        ).format(
            iterable_identifier=iterable_identifier,
            member=self.member_validator,
        )


def deep_iterable(member_validator, iterable_validator=None):
    """
    A validator that performs deep validation of an iterable.

    :param member_validator: Validator to apply to iterable members
    :param iterable_validator: Validator to apply to iterable itself
        (optional)

    .. versionadded:: 19.1.0

    :raises TypeError: if any sub-validators fail
    """
    return _DeepIterable(member_validator, iterable_validator)


@attrs(repr=False, slots=True, hash=True)
class _DeepMapping(object):
    key_validator = attrib(validator=is_callable())
    value_validator = attrib(validator=is_callable())
    mapping_validator = attrib(default=None, validator=optional(is_callable()))

    def __call__(self, inst, attr, value):
        """
        We use a callable class to be able to change the ``__repr__``.
        """
        if self.mapping_validator is not None:
            self.mapping_validator(inst, attr, value)

        for key in value:
            self.key_validator(inst, attr, key)
            self.value_validator(inst, attr, value[key])

    def __repr__(self):
        return (
            "<deep_mapping validator for objects mapping {key!r} to {value!r}>"
        ).format(key=self.key_validator, value=self.value_validator)


def deep_mapping(key_validator, value_validator, mapping_validator=None):
    """
    A validator that performs deep validation of a dictionary.

    :param key_validator: Validator to apply to dictionary keys
    :param value_validator: Validator to apply to dictionary values
    :param mapping_validator: Validator to apply to top-level mapping
        attribute (optional)

    .. versionadded:: 19.1.0

    :raises TypeError: if any sub-validators fail
    """
    return _DeepMapping(key_validator, value_validator, mapping_validator)


@attrs(repr=False, frozen=True, slots=True)
class _NumberValidator(object):
    bound = attrib()
    compare_op = attrib()
    compare_func = attrib()

    def __call__(self, inst, attr, value):
        """
        We use a callable class to be able to change the ``__repr__``.
        """
        if not self.compare_func(value, self.bound):
            raise ValueError(
                "'{name}' must be {op} {bound}: {value}".format(
                    name=attr.name,
                    op=self.compare_op,
                    bound=self.bound,
                    value=value,
                )
            )

    def __repr__(self):
        return "<Validator for x {op} {bound}>".format(
            op=self.compare_op, bound=self.bound
        )


def lt(val):
    """
    A validator that raises `ValueError` if the initializer is called
    with a number larger or equal to *val*.

    :param val: Exclusive upper bound for values

    .. versionadded:: 21.3.0
    """
    return _NumberValidator(val, "<", operator.lt)


def le(val):
    """
    A validator that raises `ValueError` if the initializer is called
    with a number greater than *val*.

    :param val: Inclusive upper bound for values

    .. versionadded:: 21.3.0
    """
    return _NumberValidator(val, "<=", operator.le)


def ge(val):
    """
    A validator that raises `ValueError` if the initializer is called
    with a number smaller than *val*.

    :param val: Inclusive lower bound for values

    .. versionadded:: 21.3.0
    """
    return _NumberValidator(val, ">=", operator.ge)


def gt(val):
    """
    A validator that raises `ValueError` if the initializer is called
    with a number smaller or equal to *val*.

    :param val: Exclusive lower bound for values

    .. versionadded:: 21.3.0
    """
    return _NumberValidator(val, ">", operator.gt)


@attrs(repr=False, frozen=True, slots=True)
class _MaxLengthValidator(object):
    max_length = attrib()

    def __call__(self, inst, attr, value):
        """
        We use a callable class to be able to change the ``__repr__``.
        """
        if len(value) > self.max_length:
            raise ValueError(
                "Length of '{name}' must be <= {max}: {len}".format(
                    name=attr.name, max=self.max_length, len=len(value)
                )
            )

    def __repr__(self):
        return "<max_len validator for {max}>".format(max=self.max_length)


def max_len(length):
    """
    A validator that raises `ValueError` if the initializer is called
    with a string or iterable that is longer than *length*.

    :param int length: Maximum length of the string or iterable

    .. versionadded:: 21.3.0
    """
    return _MaxLengthValidator(length)