Ref.py

"""
Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
SPDX-License-Identifier: MIT-0
"""
from cfnlint.rules import CloudFormationLintRule
from cfnlint.rules import RuleMatch


class Ref(CloudFormationLintRule):
    """Check if Ref value is a string"""

    id = 'E1020'
    shortdesc = 'Ref validation of value'
    description = (
        'Making sure the Ref has a String value (no other functions are supported)'
    )
    source_url = 'https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference-ref.html'
    tags = ['functions', 'ref']

    def match(self, cfn):
        matches = []

        ref_objs = cfn.search_deep_keys('Ref')
        for ref_obj in ref_objs:
            value = ref_obj[-1]
            if not isinstance(value, (str)):
                message = 'Ref can only be a string for {0}'
                matches.append(
                    RuleMatch(
                        ref_obj[:-1], message.format('/'.join(map(str, ref_obj[:-1])))
                    )
                )

        return matches