Check NestedStack diffs

nested-stack-diff.sh

#!/bin/bash -e

cdk synth > /dev/null

color=${1:-'--color'}

for stack_name in ${YOUR_PARENT_STACK_NAMES}; do
  resources=$(aws cloudformation list-stack-resources --stack-name ${stack_name})
  length=$(echo ${resources} | jq '.StackResourceSummaries | length')

  for i in $(seq 0 $(expr ${length} - 1)); do
    summaries=$(echo ${resources} | jq ".StackResourceSummaries[${i}]")

    [ "$(echo ${summaries} | jq -r '.ResourceType')" != 'AWS::CloudFormation::Stack' ] && continue

    aws cloudformation get-template --stack-name $(echo ${summaries} | jq -r '.PhysicalResourceId') | jq '.TemplateBody' > template.json

    resource_id=$(echo ${summaries} | jq -r '.LogicalResourceId')
    stack_id=$(echo ${resource_id} | sed -e 's/NestedStack.*//')
    file=$(find . -name "${stack_name}${stack_id}*.nested.template.json")
    diff=$(json-diff ${color} template.json ${file} || true)

    [ "${diff}" ] || continue

    echo '------------------------------------------------------------------'
    echo ${resource_id}
    echo '------------------------------------------------------------------'
    echo -e "${diff}"
  done
done

rm -f template.json

Thanks for the inspiration! Did have a need for a Python version.

import boto3 
import json
import glob
import sys
from subprocess import run
import difflib

try:
    from colorama import Fore, Back, Style, init
    init()
except ImportError:  # fallback so that the imported classes always exist
    class ColorFallback():
        __getattr__ = lambda self, name: ''
    Fore = Back = Style = ColorFallback()

def color_diff(diff):
    for line in diff:
        if line.startswith('+'):
            yield Fore.GREEN + line + Fore.RESET
        elif line.startswith('-'):
            yield Fore.RED + line + Fore.RESET
        elif line.startswith('^'):
            yield Fore.BLUE + line + Fore.RESET
        else:
            yield line

def confirm(msg="Do you want to continue?"):
    return input(f"{msg} ").lower() in ('yes', 'y')

def cdk_diff_nested_stack(stack_name):
    """
    Colorfull diff between local changes to CDK and what is deployed
    """
    cf_client = boto3.client("cloudformation")
    responce = cf_client.list_stack_resources(StackName=stack_name)
    resource_summeries = responce['StackResourceSummaries']
    for resource in resource_summeries:
        if 'AWS::CloudFormation::Stack' in resource['ResourceType']:
            nested_stack_name_arn = resource['PhysicalResourceId']
            nested_response = cf_client.get_template(StackName=nested_stack_name_arn)
            template = nested_response['TemplateBody']
            nested_stack_name = resource['LogicalResourceId'].split('NestedStack')[0]
            print_stack_name = f'###  {nested_stack_name}  ###'
            print(print_stack_name)
            print('#'*len(print_stack_name))
            nested_files = glob.glob(f'./cdk.out/*{nested_stack_name}*.nested.template.json')
            nested_file = [ns for ns in nested_files if 'Provider' not in ns][0]
            template_json = json.dumps(template, indent=2)
            json_file = open(nested_file)
            txt = json_file.read()
            json_file.close()
            #print(txt)
            diff = difflib.ndiff(template_json.split('\n'), txt.split('\n'))
            diff = color_diff(diff)
            print('\n'.join(diff))
            print('---')
            if not confirm(msg='Continue with next stack diff?'):
                sys.exit(1)
            print('---')


if __name__ == "__main__":
    root_stack_name = "RootCdkStackName"
    run(['cdk', 'synth', '--quiet'])
    cdk_diff_nested_stack(root_stack_name)