Source code for runway.cfngin.lookups.handlers.envvar

"""Environment variable lookup."""

import logging
import os
from typing import Any, ClassVar

from ....lookups.handlers.base import LookupHandler
from ...utils import read_value_from_path

LOGGER = logging.getLogger(__name__)




class EnvvarLookup(LookupHandler[Any]):
    """Environment variable lookup."""

    DEPRECATION_MSG = "envvar Lookup has been deprecated; use the env lookup instead"
    TYPE_NAME: ClassVar[str] = "envvar"
    """Name that the Lookup is registered as."""



    @classmethod
    def handle(cls, value: str, *_args: Any, **_: Any) -> str:
        """Retrieve an environment variable.

        Args:
            value: Parameter(s) given to this lookup.

        Example:
            ::

                # With CFNgin we would reference the environment variable like this:
                conf_key: ${envvar ENV_VAR_NAME}

            You can optionally store the value in a file, ie::

                $ cat envvar_value.txt
                ENV_VAR_NAME

            and reference it within CFNgin (NOTE: the path should be relative
            to the CFNgin config file)::

                conf_key: ${envvar file://envvar_value.txt}

                # Both of the above would resolve to
                conf_key: ENV_VALUE

        """
        LOGGER.warning("${envvar %s}: %s: ${env %s}", value, cls.DEPRECATION_MSG, value)
        value = read_value_from_path(value)

        try:
            return os.environ[value]
        except KeyError as exc:
            raise ValueError(f'EnvVar "{value}" does not exist') from exc