Source code for runway.lookups.handlers.var

"""Retrieve a variable from the variables file or definition.

If the Lookup is unable to find an defined variable matching the
provided query, the default value is returned or a ``ValueError`` is raised
if a default value was not provided.

Nested values can be used by providing the full path to the value but, it
will not select a list element.

The returned value can contain any YAML support data type
(dictionaries/mappings/hashes, lists/arrays/sequences, strings, numbers,
and booleon).

.. rubric:: Arguments

This Lookup supports all :ref:`Common Lookup Arguments` but, the folling have
limited or no effect:

- region

.. rubric:: Example
.. code-block:: yaml

    - modules:
        - path: sampleapp.cfn
            ami_id: ${var ami_id.${env AWS_REGION}}
        SOME_VARIABLE: ${var some_variable::default=default}

# pylint: disable=arguments-differ
import logging
from typing import TYPE_CHECKING, Any  # pylint: disable=unused-import

from .base import LookupHandler

# python2 supported pylint sees this is cyclic even though its only for type checking
# pylint: disable=cyclic-import
    from ...context import Context  # noqa: F401 pylint: disable=unused-import

LOGGER = logging.getLogger(__name__)
TYPE_NAME = "var"

[docs]class VarLookup(LookupHandler): """Variable definition Lookup."""
[docs] @classmethod def handle(cls, value, context, **kwargs): # type: (str, 'Context', Any) -> Any """Retrieve a variable from the variable definition. The value is retrieved from the variables passed to Runway using either a variables file or the ``variables`` directive of the config file. Args: value: The value passed to the Lookup. variables: The resolved variables pass to Runway. Raises: ValueError: Unable to find a value for the provided query and a default value was not provided. """ query, args = cls.parse(value) variables = kwargs["variables"] result = variables.find(query, default=args.pop("default", "")) if result != "": # allows for False bool and NoneType results return cls.format_results(result, **args) raise ValueError('"{}" does not exist in the variable definition'.format(query))