Used.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 Used(CloudFormationLintRule):
    """Check if Conditions are configured correctly"""

    id = 'W8001'
    shortdesc = 'Check if Conditions are Used'
    description = 'Making sure the conditions defined are used'
    source_url = 'https://github.com/aws-cloudformation/cfn-python-lint'
    tags = ['conditions']

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

        conditions = cfn.template.get('Conditions', {})
        if conditions:
            # Get all "If's" that reference a Condition
            iftrees = cfn.search_deep_keys('Fn::If')

            for iftree in iftrees:
                if isinstance(iftree[-1], list):
                    ref_conditions.append(iftree[-1][0])
                else:
                    ref_conditions.append(iftree[-1])

            # Get conditions used by another condition
            condtrees = cfn.search_deep_keys('Condition')

            for condtree in condtrees:
                if condtree[0] == 'Conditions':
                    if isinstance(condtree[-1], (str)):
                        ref_conditions.append(condtree[-1])

            # Get resource's Conditions
            for _, resource_values in cfn.get_resources().items():
                if 'Condition' in resource_values:
                    ref_conditions.append(resource_values['Condition'])

            # Get Output Conditions
            for _, output_values in cfn.template.get('Outputs', {}).items():
                if 'Condition' in output_values:
                    ref_conditions.append(output_values['Condition'])

            # Check if the confitions are used
            for condname, _ in conditions.items():
                if condname not in ref_conditions:
                    message = 'Condition {0} not used'
                    matches.append(
                        RuleMatch(['Conditions', condname], message.format(condname))
                    )

        return matches