Source code for split_settings.tools

"""
Organize Django settings into multiple files and directories.

Easily override and modify settings. Use wildcards and optional
settings files.
"""

import glob
import inspect
import os
import sys
from importlib.util import module_from_spec, spec_from_file_location

__all__ = ('optional', 'include')  # noqa: WPS410

#: Special magic attribute that is sometimes set by `uwsgi` / `gunicord`.
_INCLUDED_FILE = '__included_file__'


def optional(filename: str) -> str:
    """
    This functions is used for compatibility reasons.

    It masks the old `optional` class with the name error.
    Now `invalid-name` is removed from `pylint`.

    Args:
        filename: the filename to be optional.

    Returns:
        New instance of :class:`_Optional`.

    """
    return _Optional(filename)


class _Optional(str):  # noqa: WPS600
    """
    Wrap a file path with this class to mark it as optional.

    Optional paths don't raise an :class:`IOError` if file is not found.
    """


def include(*args: str, **kwargs) -> None:  # noqa: WPS210, WPS231, C901
    """
    Used for including Django project settings from multiple files.

    Args:
        *args: File paths (``glob`` - compatible wildcards can be used).
        **kwargs: Settings context: ``scope=globals()`` or ``None``.

    Raises:
        IOError: if a required settings file is not found.

    Usage example:

    .. code:: python

        from split_settings.tools import optional, include

        include(
            'components/base.py',
            'components/database.py',
            optional('local_settings.py'),

            scope=globals(),  # optional scope
        )

    """
    # we are getting globals() from previous frame
    # globals - it is caller's globals()
    scope = kwargs.pop('scope', inspect.stack()[1][0].f_globals)

    scope.setdefault('__included_files__', [])
    included_files = scope.get('__included_files__')

    including_file = scope.get(
        _INCLUDED_FILE,
        scope['__file__'].rstrip('c'),
    )
    conf_path = os.path.dirname(including_file)

    for conf_file in args:
        saved_included_file = scope.get(_INCLUDED_FILE)
        pattern = os.path.join(conf_path, conf_file)

        # find files per pattern, raise an error if not found
        # (unless file is optional)
        files_to_include = glob.glob(pattern)
        if not files_to_include and not isinstance(conf_file, _Optional):
            raise IOError('No such file: {0}'.format(pattern))

        for included_file in files_to_include:
            included_file = os.path.abspath(included_file)  # noqa: WPS440
            if included_file in included_files:
                continue

            included_files.append(included_file)

            scope[_INCLUDED_FILE] = included_file
            with open(included_file, 'rb') as to_compile:
                compiled_code = compile(  # noqa: WPS421
                    to_compile.read(), included_file, 'exec',
                )
                exec(compiled_code, scope)  # noqa: S102, WPS421

            # Adds dummy modules to sys.modules to make runserver autoreload
            # work with settings components:
            rel_path = os.path.relpath(included_file)
            module_name = '_split_settings.{0}'.format(
                rel_path[:rel_path.rfind('.')].replace('/', '.'),
            )

            spec = spec_from_file_location(module_name, included_file)
            module = module_from_spec(spec)  # type: ignore
            sys.modules[module_name] = module
        if saved_included_file:
            scope[_INCLUDED_FILE] = saved_included_file
        elif _INCLUDED_FILE in scope:
            scope.pop(_INCLUDED_FILE)