Split.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 Split(CloudFormationLintRule):
    """Check if Split values are correct"""

    id = 'E1018'
    shortdesc = 'Split validation of parameters'
    description = 'Making sure the split function is properly configured'
    source_url = 'https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference-split.html'
    tags = ['functions', 'split']

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

        split_objs = cfn.search_deep_keys('Fn::Split')

        supported_functions = [
            'Fn::Base64',
            'Fn::FindInMap',
            'Fn::GetAZs',
            'Fn::GetAtt',
            'Fn::If',
            'Fn::ImportValue',
            'Fn::Join',
            'Fn::Select',
            'Fn::Sub',
            'Ref',
            'Fn::ToJsonString',
        ]

        for split_obj in split_objs:
            split_value_obj = split_obj[-1]
            tree = split_obj[:-1]
            if isinstance(split_value_obj, list):
                if len(split_value_obj) == 2:
                    split_delimiter = split_value_obj[0]
                    split_string = split_value_obj[1]
                    if not isinstance(split_delimiter, str):
                        message = 'Split delimiter has to be of type string for {0}'
                        matches.append(
                            RuleMatch(
                                tree + [0], message.format('/'.join(map(str, tree)))
                            )
                        )
                    if isinstance(split_string, dict):
                        if len(split_string) == 1:
                            for key, _ in split_string.items():
                                if key not in supported_functions:
                                    message = 'Fn::Split doesn\'t support the function {0} at {1}'
                                    matches.append(
                                        RuleMatch(
                                            tree + [key],
                                            message.format(
                                                key, '/'.join(map(str, tree))
                                            ),
                                        )
                                    )
                        else:
                            message = (
                                'Split list of singular function or string for {0}'
                            )
                            matches.append(
                                RuleMatch(
                                    tree, message.format('/'.join(map(str, tree)))
                                )
                            )
                    elif not isinstance(split_string, str):
                        message = (
                            'Split has to be of type string or valid function for {0}'
                        )
                        matches.append(
                            RuleMatch(tree, message.format('/'.join(map(str, tree))))
                        )
                else:
                    message = 'Split should be an array of 2 for {0}'
                    matches.append(
                        RuleMatch(tree, message.format('/'.join(map(str, tree))))
                    )
            else:
                message = 'Split should be an array of 2 for {0}'
                matches.append(
                    RuleMatch(tree, message.format('/'.join(map(str, tree))))
                )
        return matches