field.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
Schema fields.

These fields produce better validation errors than the standard
:mod:`zope.schema` fields do. All the standard fields are also aliased
to be imported from this module.

.. TODO: This module is big enough it should be factored into a package and sub-modules.
"""

from __future__ import absolute_import
from __future__ import division
from __future__ import print_function

# stdlib imports
import numbers
import re

try:
    import collections.abc as abcs
except ImportError: # pragma: no cover
    # Python 2
    import collections as abcs

from six import string_types
from six import text_type
from zope import interface
from zope import schema
from zope.deferredimport import deprecatedFrom

from zope.event import notify
import zope.interface.common.idatetime
from zope.cachedescriptors.property import Lazy

from zope.schema import interfaces as sch_interfaces
from zope.schema.interfaces import IFromBytes
from zope.schema.interfaces import IFromUnicode
from zope.schema.interfaces import InvalidValue

from zope.schema import Bool
from zope.schema import Choice
from zope.schema import Date
from zope.schema import Datetime
from zope.schema import Decimal
from zope.schema import Dict
from zope.schema import FrozenSet
from zope.schema import Iterable
from zope.schema import List
from zope.schema import Mapping
from zope.schema import MutableMapping
from zope.schema import MutableSequence
from zope.schema import Sequence
from zope.schema import Set
from zope.schema import Text
from zope.schema import TextLine
from zope.schema import Timedelta
from zope.schema import Tuple
from zope.schema import Object as _ObjectBase

from zope.schema import Complex
from zope.schema import Real
from zope.schema import Rational
from zope.schema import Integral

from nti.schema import MessageFactory as _
from nti.schema.interfaces import BeforeDictAssignedEvent
from nti.schema.interfaces import BeforeObjectAssignedEvent
from nti.schema.interfaces import BeforeSchemaFieldAssignedEvent
from nti.schema.interfaces import BeforeSequenceAssignedEvent
from nti.schema.interfaces import BeforeSetAssignedEvent
from nti.schema.interfaces import BeforeTextAssignedEvent
from nti.schema.interfaces import BeforeTextLineAssignedEvent
from nti.schema.interfaces import IFromObject
from nti.schema.interfaces import IListOrTuple
from nti.schema.interfaces import IVariant
from nti.schema.interfaces import VariantValidationError


__docformat__ = "restructuredtext en"

# Re-export some things as part of our public API so we can
# later re-implement them locally if needed
__all__ = [
    'Bool',
    'Choice',
    'Complex',
    'Date',
    'Datetime',
    'Decimal',
    'DecodingValidTextLine',
    'Dict',
    'DictFromObject',
    'FieldValidationMixin',
    'Float',
    'FrozenSet',
    'HTTPURL',
    'IndexedIterable',
    'Int',
    'Integral',
    'Iterable',
    'List',
    'ListOrTuple',
    'ListOrTupleFromObject',
    'Mapping',
    'MutableMapping',
    'MutableSequence',
    'Number',
    'Object',
    'ObjectLen',
    'Rational',
    'Real',
    'Set',
    'Sequence',
    'StrippedValidTextLine',
    'Text',
    'TextLine',
    'Timedelta',
    'Tuple',
    'TupleFromObject',
    'UniqueIterable',
    'ValidBytes',
    'ValidBytesLine',
    'ValidChoice',
    'ValidDatetime',
    'ValidRegEx',
    'ValidRegularExpression',
    'ValidSet',
    'ValidText',
    'ValidTextLine',
    'ValidURI',
    'Variant',
]

# BWC alias, not in __all__
DateTime = Datetime

deprecatedFrom(
    "Moved to nti.schema.schema",
    "nti.schema.schema",
    'SchemaConfigured',
)


def _do_set(self, context, value, cls, factory):
    try:
        event = factory(value, self.__name__, context)
        notify(event)
        value = event.object
        super(cls, self).set(context, value)
    except sch_interfaces.ValidationError as e: # pragma: no cover
        # This shouldn't happen, set() doesn't typically validate.
        self._reraise_validation_error(e, value) # pylint:disable=protected-access

def __make_set(cls, eventfactory):

    def set(self, context, value): # pylint:disable=redefined-builtin
        return _do_set(self, context, value, cls, eventfactory)

    cls.set = set

def __with_set(eventfactory=BeforeSchemaFieldAssignedEvent):
    def X(cls):
        __make_set(cls, eventfactory)
        return cls
    return X

def _fixup_Object_field(field, early_error=False):
    # If possible, make the field provide IFromObject
    if not IFromObject.providedBy(field):
        if isinstance(field, _ObjectBase):
            # An object field can do this with a tiny bit of help.
            def _object_fromObject(value):
                if not field.schema.providedBy(value) and value != field.missing_value:
                    # Allow the TypeError or LookupError to propagate,
                    # signalling nti.externalization that it doesn't need to
                    # try to adapt again.
                    value = field.schema(value)
                field.validate(value)
                return value
            field.fromObject = _object_fromObject
            interface.alsoProvides(field, IFromObject)
        elif sch_interfaces.ICollection.providedBy(field):
            # Has a value_type
            try:
                # pylint:disable=protected-access
                _SequenceFromObjectMixin._validate_contained_field(field.value_type)
            except sch_interfaces.SchemaNotProvided:
                # Nothing we can do
                pass
            else:
                def _collection_fromObject(value):
                    return _SequenceFromObject(field).fromObject(value)
                field.fromObject = _collection_fromObject
                interface.alsoProvides(field, IFromObject)
        elif sch_interfaces.IMapping.providedBy(field):
            # Has a value_type and key_type
            try:
                # pylint:disable=protected-access
                _SequenceFromObjectMixin._validate_contained_field(field.value_type,
                                                                   required=True,
                                                                   early_error=early_error)
                _SequenceFromObjectMixin._validate_contained_field(field.key_type,
                                                                   required=True,
                                                                   early_error=early_error)
            except sch_interfaces.RequiredMissing:
                # Previously, we could pass with None for the key or value. That *will*
                # blow up in the fromObject case, though. So now we don't add IFromObject
                # that we *know* will blow up. Further, we raise this error so that the invalid
                # Dict gets caught, when requested
                if early_error:
                    raise
            except sch_interfaces.SchemaNotProvided:
                # Nothing to add.
                pass
            else:
                def _map_fromObject(value):
                    return _MapFromObject(field).fromObject(value)
                field.fromObject = _map_fromObject
                interface.alsoProvides(field, IFromObject)
    return field


class FieldValidationMixin(object):
    """
    A field mixin that causes slightly better errors to be created.
    """

    @property
    def __fixup_name__(self):
        """
        The :class:`zope.schema.fieldproperty.FieldPropertyStoredThroughField` class mangles
        the field name; this undoes that mangling.

        .. seealso:: `nti.schema.fieldproperty.field_name`
        """
        from nti.schema.fieldproperty import field_name
        return field_name(self)

    def _fixup_validation_error_args(self, e, value):
        # Called when the exception has one argument, which is usually, though not always,
        # the message
        e.args = (value, e.args[0], self.__fixup_name__)

    def _fixup_validation_error_no_args(self, e, value):
        # Called when there are no arguments
        e.args = (value, str(e), self.__fixup_name__)

    def _reraise_validation_error(self, e, value, _raise=False):
        # This must be called inside a try/except with an active exception.
        assert e.field is not None, "A _validate method failed to use ex.with_field_and_value()"
        # As-of zope.schema 4.7.0, this is largely obsolete.
        # Arguments are provided; we stop calling this in many cases.
        if len(e.args) == 1:  # typically the message is the only thing
            self._fixup_validation_error_args(e, value)
        elif not e.args:
            self._fixup_validation_error_no_args(e, value)
        if _raise:
            raise e
        raise # pylint:disable=misplaced-bare-raise

    def _fixup_too_short(self, e, value):
        # Note we're capitalizing the field in the message.
        e.i18n_message = _(
            u'${field} is too short. Please use at least one character.',
            msgid_plural=u'${field} is too short. Please use at least ${minLength} characters.',
            mapping={'field': self.__fixup_name__.capitalize(),
                     'minLength': e.bound},
            number=e.bound
        )
        e.args = (self.__fixup_name__.capitalize() + ' is too short.',
                  self.__fixup_name__,
                  value)

    def _fixup_too_long(self, e, value):
        e.i18n_message = _(
            u'${field} is too long. ${max_size} character limit.',
            mapping={'field': self.__fixup_name__.capitalize(),
                     'max_size': e.bound}
        )
        e.args = (self.__fixup_name__.capitalize() + ' is too long.',
                  self.__fixup_name__,
                  value)

    def _validate(self, value):
        try:
            super(FieldValidationMixin, self)._validate(value)
        except sch_interfaces.WrongType as e:
            assert e.expected_type is not None, "The expected_type should be provided"
            raise
        except sch_interfaces.WrongContainedType:
            raise
        except sch_interfaces.TooShort as e:
            self._fixup_too_short(e, value)
            raise
        except sch_interfaces.TooLong as e:
            self._fixup_too_long(e, value)
            raise
        except sch_interfaces.SchemaNotProvided as e:
            assert e.schema is not None, "The schema should be provided"
            raise
        except sch_interfaces.OutOfBounds as e:
            assert e.bound is not None, "The bound should be provided"
            raise
        except sch_interfaces.ValidationError as e:
            self._reraise_validation_error(e, value)


@interface.implementer(sch_interfaces.IObject)
class ValidDatetime(FieldValidationMixin, Datetime):
    """
    Unlike the standard datetime, this will check that the
    given object is an instance of IDatetime, and raise
    the same error as object does.
    """

    schema = zope.interface.common.idatetime.IDateTime

    def _validate(self, value):
        try:
            super(ValidDatetime, self)._validate(value)
        except sch_interfaces.WrongType as e:
            raise sch_interfaces.SchemaNotProvided(
                value, e.__doc__,
                self.__fixup_name__, self.schema,
                list(interface.providedBy(value))).with_field_and_value(self, value)

        # schema has to be provided by value
        if not self.schema.providedBy(value):  # pragma: no cover
            raise sch_interfaces.SchemaNotProvided().with_field_and_value(self, value)

def _iteritems(o):
    meth = getattr(o, 'iteritems', None) or getattr(o, 'items')
    return meth()

class Object(FieldValidationMixin, _ObjectBase):
    """
    Improved ``zope.schema.Object``.
    """

class _FieldConverter(object):

    def __init__(self, field):
        self.field = field

    @Lazy
    def fromObject(self):
        return getattr(self.field, 'fromObject', None)

    @Lazy
    def fromUnicode(self):
        return getattr(self.field, 'fromUnicode', None)

    @Lazy
    def fromBytes(self):
        return getattr(self.field, 'fromBytes', None)

    def __call__(self, value):
        # pylint:disable=too-many-function-args

        # Take make it easier on implementers of fromObject,
        # if they also implement fromBytes/fromUnicode, we call those
        # first.
        if isinstance(value, bytes) and self.fromBytes is not None:
            return self.fromBytes(value)

        if isinstance(value, text_type) and self.fromUnicode is not None:
            return self.fromUnicode(value)

        if self.fromObject is not None:
            return self.fromObject(value)

        # Last resort, see if it can be validated by the field as-is.
        # Let this raise whatever error it wants to, but be sure
        # validation errors have the details filled in.
        try:
            self.field.validate(value)
            return value
        except sch_interfaces.ValidationError as ex:
            if ex.field is None:
                ex.field = self.field
            if ex.value is None:
                ex.value = value
            raise


@interface.implementer(IVariant)
class Variant(FieldValidationMixin, schema.Field):
    """
    Similar to :class:`zope.schema.Object`, but accepts one of many
    non-overlapping interfaces.

    .. versionchanged:: 1.9.0

        Implementations of :class:`zope.schema.interfaces.ICollection`
        (like :class:`zope.schema.List`) and
        :class:`zope.schema.interfaces.IMapping` (like
        :class:`zope.schema.Dict`) will automatically be given a ``fromObject`` method
        when they are used as a field of this object *if* their *value_type* is an
        :class:`zope.schema.interfaces.IObject` (recursively).

    .. versionchanged:: 1.16.0
       If one of the fields of the variant is (recursively) a ``IMapping``
       such as a ``Dict``, both the key and value type must be specified. Previously,
       if they were left ``None``, a validation-time :exc:`AttributeError`
       would be raised. Now, constructing the variant will raise a ``RequiredMissing``.
    """

    fields = ()

    def __init__(self, fields, variant_raise_when_schema_provided=False, **kwargs):
        """
        :param fields: A list or tuple of field instances.
        :keyword variant_raise_when_schema_provided: If ``True``, then
            if a value is provided to ``validate`` that implements
            the schema of a particular field, and that field raised
            a validation error, that error will be propagated instead
            of the error raised by the last field, and no additional fields
            will be asked to do validation.
        """
        if not fields or not all((sch_interfaces.IField.providedBy(x) for x in fields)):
            raise sch_interfaces.SchemaNotProvided(sch_interfaces.IField)

        # assign our children first so anything we copy to them as a result of the super
        # constructor (__name__) gets set
        self.fields = [_fixup_Object_field(field, early_error=True) for field in fields]
        for f in self.fields:
            f.__parent__ = self

        self._raise_when_provided = variant_raise_when_schema_provided
        super(Variant, self).__init__(**kwargs)

    def __get_name(self):
        return self.__dict__.get('__name__', '')

    def __set_name(self, name):
        self.__dict__['__name__'] = name
        for field in self.fields:
            field.__name__ = name
    __name__ = property(__get_name, __set_name)

    def getExtraDocLines(self):
        lines = super(Variant, self).getExtraDocLines()
        lines.append(".. rubric:: Possible Values")

        for field in self.fields:
            lines.append(".. rubric:: Option")
            lines.append(field.getDoc())

        return lines

    def __repr__(self):
        return "<%s.%s at 0x%x name=%r interface=%r context=%r fields=%r>" % (
            type(self).__module__, type(self).__name__,
            id(self), self.__name__,
            self.interface, self.context, self.fields
        )

    def bind(self, context):
        # The fields member really does exist
        # pylint:disable=no-member
        clone = super(Variant, self).bind(context)
        clone.fields = [x.bind(context) for x in clone.fields]
        for f in clone.fields:
            f.__parent__ = clone
        return clone

    def _validate(self, value):
        super(Variant, self)._validate(value)
        errors = []
        for field in self.fields:
            try:
                field.validate(value)
                # one of them accepted, yay!
                return
            except sch_interfaces.ValidationError as e:
                if (self._raise_when_provided
                        and hasattr(field, 'schema')
                        and field.schema.providedBy(value)):
                    self._reraise_validation_error(e, value)
                    raise AssertionError("This is never reached")

                errors.append(e)
        try:
            raise VariantValidationError(self, value, errors)
        finally:
            # break cycles
            e = errors = None

    def fromObject(self, obj):
        """
        Similar to `fromUnicode`, attempts to turn the given object
        into something acceptable and valid for this field. Raises a
        `~.VariantValidationError` if this isn't possible. Adaptation
        is attempted in the order in which fields were given to the
        constructor. Some fields cannot be used to adapt.

        .. versionchanged:: 1.8.0
           Raise `~.VariantValidationError` instead of whatever
           last error we got.
        .. versionchanged:: 1.9.1
           Respect ``self.missing_value`` and don't raise an exception
           if it is passed to this method and we're not required.
        """
        if obj == self.missing_value:
            if self.required:
                raise sch_interfaces.RequiredMissing(self.__name__).with_field_and_value(self, obj)

            # If we're not required, we still attempt all the adaptation steps
            # just in case some field can convert us very nicely, but
            # we won't raise the final exception

        errors = []

        for field in self.fields:
            try:
                converter = _FieldConverter(field)

                # Try to convert and validate. This calls fromXXX
                # if defined, and otherwise validates. The fromXXX methods
                # are also supposed to validate, so validation should be done
                # when this returns.
                return converter(obj)
            except (TypeError, sch_interfaces.ValidationError) as ex:
                # Nope, no good
                errors.append(ex)

        # We get here if nothing worked.
        if obj == self.missing_value:
            # Well it's the missing value. By definition we're not required
            # at this point (we would have raised already), so we can just return it.
            assert not self.required
            return self.missing_value

        try:
            raise VariantValidationError(self, obj, errors)
        finally:
            # break cycles
            ex = errors = None

    _EVENT_TYPES = (
        (string_types, BeforeTextAssignedEvent),
        (abcs.Mapping, BeforeDictAssignedEvent),
        (abcs.Sequence, BeforeSequenceAssignedEvent),
        (object, BeforeObjectAssignedEvent)
    )

    def set(self, context, value): # pylint:disable=arguments-differ
        # Try to determine the most appropriate event to fire
        # Order matters. It would kind of be nice to direct this to the appropriate
        # field itself, but that's sort of hard.
        for kind, factory in self._EVENT_TYPES:
            if isinstance(value, kind):
                _do_set(self, context, value, Variant, factory)
                return

class ObjectLen(FieldValidationMixin, schema.MinMaxLen, _ObjectBase):  # order matters
    """
    Allows specifying a length for arbitrary object fields (though the
    objects themselves must support the `len` function.
    """

    def __init__(self, sch, min_length=0, max_length=None, **kwargs):
        # match the calling sequence of Object, which uses a non-keyword
        # argument for schema.
        # But to work with the superclass, we have to pass it as a keyword arg.
        # it's weird.
        super(ObjectLen, self).__init__(schema=sch,
                                        min_length=min_length,
                                        max_length=max_length,
                                        **kwargs)

class Int(FieldValidationMixin, schema.Int):

    def fromUnicode(self, value):
        # Allow empty strings
        result = super(Int, self).fromUnicode(value) if value else None
        return result

class Float(FieldValidationMixin, schema.Float):

    def fromUnicode(self, value):
        result = super(Float, self).fromUnicode(value) if value else None
        return result

class Number(FieldValidationMixin, schema.Float):
    """
    A field that parses like a float from a string, but accepts any number.

    .. deprecated:: 1.4.0
       Use :class:`zope.schema.Number` if you really want arbitrary
       numbers (including fractions and decimals). You probably want
       :class:`zope.schema.Real` instead, though.
    """
    _type = numbers.Number

@__with_set()
class ValidChoice(FieldValidationMixin, schema.Choice):
    pass

@__with_set()
class ValidBytesLine(FieldValidationMixin, schema.BytesLine):
    pass

@__with_set()
class ValidBytes(FieldValidationMixin, schema.Bytes):
    pass

@__with_set(BeforeTextAssignedEvent)
class ValidText(FieldValidationMixin, schema.Text):
    """
    A text line that produces slightly better error messages. They will all
    have the 'field' property.

    We also fire :class:`IBeforeTextAssignedEvent`, which the normal
    mechanism does not.
    """

@__with_set(BeforeTextLineAssignedEvent)
class ValidTextLine(FieldValidationMixin, schema.TextLine):
    """
    A text line that produces slightly better error messages. They will all
    have the 'field' property.

    We also fire :class:`IBeforeTextLineAssignedEvent`, which the normal
    mechanism does not.
    """

@interface.implementer(sch_interfaces.IFromBytes)
class DecodingValidTextLine(ValidTextLine):
    """
    A text type that will attempt to decode non-unicode
    data as UTF-8.

    This primarily exists for legacy support (tests and persisted data).
    """

    def validate(self, value):
        if isinstance(value, bytes):
            value = value.decode('utf-8')  # let raise UnicodeDecodeError
        super(DecodingValidTextLine, self).validate(value)
        return value # tests

    # fromUnicode calls validate, so no need to duplicate

    def fromBytes(self, value):
        return self.fromUnicode(value.decode('utf-8'))


_not_stripped = r"^\s|\s$"  # space at either beginning or end
_not_stripped = re.compile(_not_stripped).search


def _is_stripped(value):
    return not _not_stripped(value)


class StrippedValidTextLine(DecodingValidTextLine):
    """
    A text line that strips whitespace from incoming values.

    .. versionadded:: 1.13.0

    .. versionchanged:: 1.13.1
           Handle single character values correctly.
    """

    def fromUnicode(self, value):
        v = value.strip() if value else value
        result = super(StrippedValidTextLine, self).fromUnicode(v)
        return result

    def _validate(self, value):
        super(StrippedValidTextLine, self)._validate(value)
        if not value or _is_stripped(value):
            return

        raise InvalidValue(value).with_field_and_value(self, value)

class ValidRegularExpression(ValidTextLine):

    def __init__(self, pattern, flags=(re.U|re.I|re.M), *args, **kwargs): # pylint:disable=keyword-arg-before-vararg
        # XXX: How would we actually fix this? It should be possible on
        # Python 3
        super(ValidRegularExpression, self).__init__(*args, **kwargs)
        self.flags = flags
        self.pattern = pattern
        self.prog = re.compile(pattern, flags)

    def constraint(self, value): # pylint:disable=method-hidden
        # If they pass a 'constraint' kwarg, it will override this.
        return self.prog.match(value) is not None

ValidRegEx = ValidRegularExpression

class ValidURI(FieldValidationMixin, schema.URI):

    def _fixup_validation_error_args(self, e, value):
        if isinstance(e, sch_interfaces.InvalidURI):
            # This class differs by using the value as the argument, not
            # a message
            e.__doc__ = e.__doc__.replace('URI', 'URL')
            e.args = (value, e.__doc__, self.__fixup_name__)
            e.message = e.i18n_message = e.__doc__
        else: # pragma: no cover
            super(ValidURI, self)._fixup_validation_error_args(e, value)

class HTTPURL(ValidURI):
    """
    A URI field that ensures and requires its value to be an absolute
    HTTP/S URL.
    """

    def fromUnicode(self, value):
        # This can wind up producing something invalid if an
        # absolute URI was already given for mailto: for whatever.
        # None of the regexs (zopes or grubers) flag that as invalid.
        # so we try to
        orig_value = value
        if value:
            lower = value.lower()
            if not lower.startswith(u'http://') and not lower.startswith(u'https://'):
                # assume http
                value = u'http://' + value
        result = super(HTTPURL, self).fromUnicode(value)
        if result.count(u':') != 1:
            self._reraise_validation_error(
                sch_interfaces.InvalidURI(orig_value).with_field_and_value(self, orig_value),
                orig_value,
                _raise=True)

        return result

class _ValueTypeAddingDocMixin(object):
    """
    A mixin for fields that wrap a value type field (e.g., Object)
    to copy the nested documentation to the parent so it is visible
    in :mod:`repoze.sphinx.autointerface`.
    """

    def getExtraDocLines(self):
        lines = super(_ValueTypeAddingDocMixin, self).getExtraDocLines()
        accept_types = getattr(self, 'accept_types', None)
        if accept_types:
            # Private helper. If it goes away or changes, making sphinx docs will
            # fail, but we shouldn't have any runtime problems.
            from zope.schema._bootstrapfields import _DocStringHelpers
            lines.append(_DocStringHelpers.make_class_field('Accepted Types', accept_types))
        return lines


@__with_set(BeforeSequenceAssignedEvent)
class IndexedIterable(_ValueTypeAddingDocMixin, FieldValidationMixin, schema.Sequence):
    """
    An arbitrary (indexable) iterable, not necessarily a list or tuple;
    either of those would be acceptable at any time (however, so would a string,
    so be careful. Try ListOrTuple if that's a problem).

    The values may be homogeneous by setting the value_type.

    .. versionchanged:: 1.4.0
       Subclass :class:`zope.schema.Sequence` instead of :class:`zope.schema.List`,
       which adds checking that the value is indeed a sequence.
    """


@interface.implementer(IListOrTuple)
class ListOrTuple(IndexedIterable):
    "Restrict sequence values specifically to list and tuple."
    _type = (list, tuple)



@interface.implementer(IFromObject)
class _SequenceFromObjectMixin(object):
    accept_types = None
    _default_type = list

    def __init__(self, *args, **kwargs):
        super(_SequenceFromObjectMixin, self).__init__(*args, **kwargs)
        self._validate_contained_field(self.value_type)

    @classmethod
    def _validate_contained_field(cls, field, required=False, early_error=False):
        # We allow None for a value type, unless required=True
        if field is None and required:
            raise sch_interfaces.RequiredMissing()
        field = _fixup_Object_field(field, early_error=early_error)
        if field is not None and not any(
                iface.providedBy(field)
                for iface
                in (IFromObject, IFromUnicode, IFromBytes)
        ):
            raise sch_interfaces.SchemaNotProvided(IFromObject, field)

    def _converter_for(self, field):
        return _FieldConverter(field)

    def _do_fromObject(self, context):
        converter = self._converter_for(self.value_type)
        result = [converter(x) for x in context]
        return result

    def _do_convert_result(self, result):
        if (isinstance(self._type, type)
                and self._type is not self._default_type):  # single type is a factory
            result = self._type(result)
        return result

    def fromObject(self, context):
        if context == self.missing_value:
            if self.required:
                raise sch_interfaces.RequiredMissing(
                    self.__name__
                ).with_field_and_value(self, context)
            # Nothing useful to do here, we're not required, don't
            # even try to convert
            return context

        check_type = self.accept_types or self._type
        if check_type is not None and not isinstance(context, check_type):
            raise sch_interfaces.WrongType(context, check_type).with_field_and_value(self, context)

        result = self._do_fromObject(context)
        return self._do_convert_result(result)


class _SequenceFromObject(_SequenceFromObjectMixin):

    def __init__(self, field):
        # We deliberately do not call the super init. The field's value_type
        # must already be valid.
        # pylint:disable=super-init-not-called
        self.__field = field

    def __getattr__(self, name):
        return getattr(self.__field, name)


class _MapFromObjectMixin(_SequenceFromObjectMixin):

    def __init__(self, *args, **kwargs):
        super(_MapFromObjectMixin, self).__init__(*args, **kwargs)
        self._validate_contained_field(self.key_type)

    def _do_convert_result(self, result):
        assert isinstance(result, dict)
        return result

    def _do_fromObject(self, context):
        key_converter = self._converter_for(self.key_type)
        value_converter = self._converter_for(self.value_type)
        return {key_converter(k): value_converter(v) for k, v in _iteritems(context)}


class _MapFromObject(_MapFromObjectMixin):

    def __init__(self, field):
        # We deliberately do not call the super init. The field's value_type
        # and key_type must already be valid.
        # pylint:disable=super-init-not-called
        self.__field = field

    def __getattr__(self, name):
        return getattr(self.__field, name)


class ListOrTupleFromObject(_SequenceFromObjectMixin, ListOrTuple):
    """
    The ``value_type`` MUST be a :class:`Variant`, or more generally,
    something supporting :class:`IFromObject`, :class:`IFromUnicode`
    or :class:`IFromBytes`.

    .. versionchanged:: 1.9.0

        Implementations of :class:`zope.schema.interfaces.ICollection`
        (like :class:`zope.schema.List`) and
        :class:`zope.schema.interfaces.IMapping` (like
        :class:`zope.schema.Dict`) will automatically be given a ``fromObject`` method
        when used as the *value_type* of this object *if* their *value_type* is an
        :class:`zope.schema.interfaces.IObject` (recursively).
    """


class TupleFromObject(_ValueTypeAddingDocMixin,
                      _SequenceFromObjectMixin,
                      FieldValidationMixin,
                      schema.Tuple):
    """
    The ``value_type`` MUST be a :class:`Variant`, or more generally,
    something supporting :class:`IFromObject`, :class:`IFromUnicode`
    or :class:`IFromBytes`.

    When setting through this object, we will automatically convert
    lists and only lists to tuples (for convenience coming in through
    JSON).

    .. versionchanged:: 1.9.0

        Implementations of :class:`zope.schema.interfaces.ICollection`
        (like :class:`zope.schema.List`) and
        :class:`zope.schema.interfaces.IMapping` (like
        :class:`zope.schema.Dict`) will automatically be given a ``fromObject`` method
        when used as the *value_type* of this object *if* their *value_type* is an
        :class:`zope.schema.interfaces.IObject` (recursively).
    """
    accept_types = (list, tuple)

    def set(self, context, value): # pylint:disable=arguments-differ
        if isinstance(value, list):
            value = tuple(value)

        _do_set(self, context, value, TupleFromObject, BeforeSequenceAssignedEvent)

    def validate(self, value):
        if isinstance(value, list):
            value = tuple(value)
        super(TupleFromObject, self).validate(value)


@__with_set(BeforeDictAssignedEvent)
class DictFromObject(_ValueTypeAddingDocMixin,
                     _MapFromObjectMixin,
                     FieldValidationMixin,
                     schema.Mapping):
    """
    The `key_type` and `value_type` must be supporting
    :class:`IFromObject` or :class:`.IFromUnicode` or :class:`IFromBytes`

    .. versionchanged:: 1.4.0
       Subclass :class:`zope.schema.Mapping` instead of :class:`zope.schema.Dict`,
       allowing for any mapping (such as BTrees), not just dicts. However, the validated
       value is still a dict.

    .. versionchanged:: 1.9.0

        Implementations of :class:`zope.schema.interfaces.ICollection`
        (like :class:`zope.schema.List`) and
        :class:`zope.schema.interfaces.IMapping` (like
        :class:`zope.schema.Dict`) will automatically be given a ``fromObject`` method
        when used as the *value_type* of this object *if* their *value_type* is an
        :class:`zope.schema.interfaces.IObject` (recursively).
    """


@__with_set(BeforeSetAssignedEvent)
class ValidSet(_ValueTypeAddingDocMixin,
               _SequenceFromObjectMixin,
               FieldValidationMixin,
               schema.Set):
    """
    A set that is validated.

    .. versionchanged:: 1.5.0
       Implement :class:`IFromObject`.

    .. versionchanged:: 1.9.0

        Implementations of :class:`zope.schema.interfaces.ICollection`
        (like :class:`zope.schema.List`) and
        :class:`zope.schema.interfaces.IMapping` (like
        :class:`zope.schema.Dict`) will automatically be given a ``fromObject`` method
        when used as the *value_type* of this object *if* their *value_type* is an
        :class:`zope.schema.interfaces.IObject` (recursively).
    """


class UniqueIterable(ValidSet):
    """
    An arbitrary iterable, not necessarily an actual :class:`set` object,
    but one whose contents are unique. Use this when you can
    return a :class:`set`, :class:`frozenset` or empty tuple. These should be
    sequences that suport the ``in`` operator.

    .. versionchanged:: 1.5.0
       Implement :class:`IFromObject`.

    .. versionchanged:: 1.9.0

        Implementations of :class:`zope.schema.interfaces.ICollection`
        (like :class:`zope.schema.List`) and
        :class:`zope.schema.interfaces.IMapping` (like
        :class:`zope.schema.Dict`) will automatically be given a ``fromObject`` method
        when used as the *value_type* of this object *if* their *value_type* is an
        :class:`zope.schema.interfaces.IObject` (recursively).
    """
    _type = None  # Override to not force a set

    def __init__(self, *args, **kwargs):
        # If they do not specify a min_length in the arguments,
        # then change it to None. This way we are compatible with
        # a generator value. Superclass specifies both a class value
        # and a default argument
        no_min_length = False
        if 'min_length' not in kwargs:
            no_min_length = True

        super(UniqueIterable, self).__init__(*args, **kwargs)
        if no_min_length:
            self.min_length = None

    def _do_convert_result(self, result):
        if not isinstance(result, (set, frozenset)):
            result = set(result)
        return result