# Source code for marshmallow.decorators

    # -*- coding: utf-8 -*-
    """Decorators for registering schema pre-processing and post-processing methods.
    These should be imported from the top-level `marshmallow` module.

    Example: ::

        from marshmallow import (
            Schema, pre_load, pre_dump, post_load, validates_schema,
            validates, fields, ValidationError
        )

        class UserSchema(Schema):

            email = fields.Str(required=True)
            age = fields.Integer(required=True)

            @post_load
            def lowerstrip_email(self, item):
                item['email'] = item['email'].lower().strip()
                return item

            @pre_load(pass_many=True)
            def remove_envelope(self, data, many):
                namespace = 'results' if many else 'result'
                return data[namespace]

            @post_dump(pass_many=True)
            def add_envelope(self, data, many):
                namespace = 'results' if many else 'result'
                return {namespace: data}

            @validates_schema
            def validate_email(self, data):
                if len(data['email']) < 3:
                    raise ValidationError('Email must be more than 3 characters', 'email')

            @validates('age')
            def validate_age(self, data):
                if data < 14:
                    raise ValidationError('Too young!')

    .. note::
        These decorators only work with instance methods. Class and static
        methods are not supported.

    .. warning::
        The invocation order of decorated methods of the same type is not guaranteed.
        If you need to guarantee order of different processing steps, you should put
        them in the same processing method.
    """
    from __future__ import unicode_literals

    import functools

    PRE_DUMP = 'pre_dump'
    POST_DUMP = 'post_dump'
    PRE_LOAD = 'pre_load'
    POST_LOAD = 'post_load'
    VALIDATES = 'validates'
    VALIDATES_SCHEMA = 'validates_schema'

    def validates(field_name):
        """Register a field validator.

        :param str field_name: Name of the field that the method validates.
        """
        return tag_processor(VALIDATES, None, False, field_name=field_name)

    def validates_schema(fn=None, pass_many=False, pass_original=False, skip_on_field_errors=True):
        """Register a schema-level validator.

        By default, receives a single object at a time, regardless of whether ``many=True``
        is passed to the `Schema`. If ``pass_many=True``, the raw data (which may be a collection)
        and the value for ``many`` is passed.

        If ``pass_original=True``, the original data (before unmarshalling) will be passed as
        an additional argument to the method.

        If ``skip_on_field_errors=True``, this validation method will be skipped whenever
        validation errors have been detected when validating fields.

        .. versionchanged:: 3.0.0b1
            ``skip_on_field_errors`` defaults to `True`.
        """
        return tag_processor(VALIDATES_SCHEMA, fn, pass_many, pass_original=pass_original,
                             skip_on_field_errors=skip_on_field_errors)

    def pre_dump(fn=None, pass_many=False):
        """Register a method to invoke before serializing an object. The method
        receives the object to be serialized and returns the processed object.

        By default, receives a single object at a time, regardless of whether ``many=True``
        is passed to the `Schema`. If ``pass_many=True``, the raw data (which may be a collection)
        and the value for ``many`` is passed.
        """
        return tag_processor(PRE_DUMP, fn, pass_many)

    def post_dump(fn=None, pass_many=False, pass_original=False):
        """Register a method to invoke after serializing an object. The method
        receives the serialized object and returns the processed object.

        By default, receives a single object at a time, transparently handling the ``many``
        argument passed to the Schema. If ``pass_many=True``, the raw data
        (which may be a collection) and the value for ``many`` is passed.
        """
        return tag_processor(POST_DUMP, fn, pass_many, pass_original=pass_original)

    def pre_load(fn=None, pass_many=False):
        """Register a method to invoke before deserializing an object. The method
        receives the data to be deserialized and returns the processed data.

        By default, receives a single datum at a time, transparently handling the ``many``
        argument passed to the Schema. If ``pass_many=True``, the raw data
        (which may be a collection) and the value for ``many`` is passed.
        """
        return tag_processor(PRE_LOAD, fn, pass_many)

    def post_load(fn=None, pass_many=False, pass_original=False):
        """Register a method to invoke after deserializing an object. The method
        receives the deserialized data and returns the processed data.

        By default, receives a single datum at a time, transparently handling the ``many``
        argument passed to the Schema. If ``pass_many=True``, the raw data
        (which may be a collection) and the value for ``many`` is passed.
        """
        return tag_processor(POST_LOAD, fn, pass_many, pass_original=pass_original)

    def tag_processor(tag_name, fn, pass_many, **kwargs):
        """Tags decorated processor function to be picked up later.

        .. note::
            Currently ony works with functions and instance methods. Class and
            static methods are not supported.

        :return: Decorated function if supplied, else this decorator with its args
            bound.
        """
        # Allow using this as either a decorator or a decorator factory.
        if fn is None:
            return functools.partial(
                tag_processor, tag_name, pass_many=pass_many, **kwargs
            )

        # Set a marshmallow_tags attribute instead of wrapping in some class,
        # because I still want this to end up as a normal (unbound) method.
        try:
            marshmallow_tags = fn.__marshmallow_tags__
        except AttributeError:
            fn.__marshmallow_tags__ = marshmallow_tags = set()
        # Also save the kwargs for the tagged function on
        # __marshmallow_kwargs__, keyed by (<tag_name>, <pass_many>)
        try:
            marshmallow_kwargs = fn.__marshmallow_kwargs__
        except AttributeError:
            fn.__marshmallow_kwargs__ = marshmallow_kwargs = {}
        marshmallow_tags.add((tag_name, pass_many))
        marshmallow_kwargs[(tag_name, pass_many)] = kwargs

        return fn