--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mercurial/thirdparty/attr/validators.py	Sun Oct 01 04:14:16 2017 -0700
@@ -0,0 +1,166 @@
+"""
+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)