python-dependency-injector/objects/catalog.py

"""
Catalog module.
"""

from .providers import Provider


class Catalog(object):
    """
    Object provides catalog.
    """

    def __init__(self, *used_providers):
        """
        Initializer.
        """
        self.__used_providers__ = set(used_providers)

    def __getattribute__(self, item):
        """
        Returns providers.

        :param item:
        :return:
        """
        attribute = super(Catalog, self).__getattribute__(item)
        if item in ('__used_providers__',):
            return attribute

        if attribute not in self.__used_providers__:
            raise AttributeError('Provider \'{}\' is not listed in '
                                 'dependencies'.format(item))
        return attribute

    @classmethod
    def __all_providers__(cls):
        """
        Returns set of all class providers.
        """
        providers = set()
        for attr_name in set(dir(cls)) - set(dir(Catalog)):
            provider = getattr(cls, attr_name)
            if not isinstance(provider, Provider):
                continue
            providers.add((attr_name, provider))
        return providers

    @classmethod
    def __override___(cls, overriding):
        """
        Overrides current catalog providers by overriding catalog providers.

        :param overriding: Catalog
        """
        overriden = overriding.__all_providers__() - cls.__all_providers__()
        for name, provider in overriden:
            overridden_provider = getattr(cls, name)
            overridden_provider.__override__(provider)


def overrides(catalog):
    """
    Catalog overriding decorator.

    :param catalog:
    :return:
    """
    def decorator(overriding_catalog):
        catalog.__override___(overriding_catalog)
        return overriding_catalog
    return decorator