loader.py

from t4 import list_packages, Package
MODULE_PATH = []


class DataPackageImporter:
    """
    Data package module loader. Executes package import code and adds the package to the
    module cache.
    """

    @classmethod
    def create_module(cls, spec):
        """
        Module creator. Returning None causes Python to use the default module creator.
        """
        return None

    @classmethod
    def exec_module(cls, module):
        """
        Module executor.
        """
        name_parts = module.__name__.split('.')

        if module.__name__ == 't4.data':
            # __path__ must be set even if the package is virtual, but can be set to [].
            module.__path__ = MODULE_PATH
            return module

        elif len(name_parts) == 3:  # e.g. module.__name__ == t4.data.foo
            namespace = name_parts[2]

            for pkg in list_packages():
                pkg_user, pkg_name = pkg.split('/')
                if pkg_user == namespace:
                    module.__dict__[pkg_name] = Package.browse(pkg)

            module.__path__ = MODULE_PATH
            return module

        else:
            assert False