(CfnInclude): Nested stack parameters must be strings

[MasonHM]

When using the CfnInclude module to import a nested stack with a 'Number' parameter and the parent stack provides an unquoted number, CDK throws an error saying:

Error: Resolution error: Supplied properties not correct for "CfnStackProps"
  parameters: element 'Number': 60 should be a string.

Changing the parameter to a quoted string (60 --> '60') in the parent template fixes the problem. In my case, this would mean changing the parameter format in dozens of locations, so I'd rather have CDK support number parameters the way I expect.

CloudFormation documentation says:

AWS CloudFormation validates the parameter value as a number; however, when you use the parameter elsewhere in your template (for example, by using the Ref intrinsic function), the parameter value becomes a string.

This problem may be related to #744.

Reproduction Steps

parent-stack.yaml:

AWSTemplateFormatVersion: '2010-09-09'

Resources:
  NestedStack:
    Type: AWS::CloudFormation::Stack
    Properties:
      TemplateURL: 'https://s3.amazonaws.com/masonme-cdk-test/templates/nested-stack.yaml'
      Parameters:
        Number: 60

nested-stack.yaml:

AWSTemplateFormatVersion: '2010-09-09'

Parameters:
  Number:
    Type: Number

Resources:
  S3Bucket:
    Type: AWS::S3::Bucket
    Properties:
      BucketName: 'testbucket1234unique'

bin/min-repro-int-param.ts:

#!/usr/bin/env node
import { App, Stack } from '@aws-cdk/core';
import { CfnInclude } from '@aws-cdk/cloudformation-include';

class NestedStackTest extends Stack {
  constructor(scope: App, id: string) {
    super(scope, id);

    const cfnTemplate = new CfnInclude(this, 'template', {
      templateFile: 'parent-stack.yaml',
      loadNestedStacks: {
        'NestedStack': {
          templateFile: 'nested-stack.yaml'
        }
      }
    });
  }
}

const app = new App();
new NestedStackTest(app, 'NestedStackTest');

What did you expect to happen?

I expected cdk synth to work correctly and generate the CloudFormation.

Expected output:

[masonme@f45c89b36d13] $ cdk synth
AWSTemplateFormatVersion: "2010-09-09"
Resources:
  NestedStack:
    Type: AWS::CloudFormation::Stack
    Properties:
      TemplateURL:
        Fn::Join:
          - ""
          - - https://s3.us-east-2.
            - Ref: AWS::URLSuffix
            - /
            - Ref: AssetParameters866b547d9ca7cbf354b8fa729a93a314c8b525c1883336492117d99e62eb7a26S3Bucket0D4E156C
            - /
            - Fn::Select:
                - 0
                - Fn::Split:
                    - "||"
                    - Ref: AssetParameters866b547d9ca7cbf354b8fa729a93a314c8b525c1883336492117d99e62eb7a26S3VersionKeyC690772D
            - Fn::Select:
                - 1
                - Fn::Split:
                    - "||"
                    - Ref: AssetParameters866b547d9ca7cbf354b8fa729a93a314c8b525c1883336492117d99e62eb7a26S3VersionKeyC690772D
      Parameters:
        Number: "60"
Parameters:
  AssetParameters866b547d9ca7cbf354b8fa729a93a314c8b525c1883336492117d99e62eb7a26S3Bucket0D4E156C:
    Type: String
    Description: S3 bucket for asset "866b547d9ca7cbf354b8fa729a93a314c8b525c1883336492117d99e62eb7a26"
  AssetParameters866b547d9ca7cbf354b8fa729a93a314c8b525c1883336492117d99e62eb7a26S3VersionKeyC690772D:
    Type: String
    Description: S3 key for asset version "866b547d9ca7cbf354b8fa729a93a314c8b525c1883336492117d99e62eb7a26"
  AssetParameters866b547d9ca7cbf354b8fa729a93a314c8b525c1883336492117d99e62eb7a26ArtifactHashF5304F6F:
    Type: String
    Description: Artifact hash for asset "866b547d9ca7cbf354b8fa729a93a314c8b525c1883336492117d99e62eb7a26"

What actually happened?

cdk synth exited with an error.

Actual output:

[masonme@f45c89b36d13] $ cdk synth

/Users/masonme/cdk-migration-test/node_modules/@aws-cdk/core/lib/runtime.ts:141
    return this.errorMessage + (childMessages.length ? `\n  ${childMessages.replace(/\n/g, '\n  ')}` : '');
            ^
Error: Resolution error: Supplied properties not correct for "CfnStackProps"
  parameters: element 'Number': 60 should be a string.
    at ValidationResult.assertSuccess (/Users/masonme/cdk-migration-test/node_modules/@aws-cdk/core/lib/runtime.ts:141:13)
    at cfnStackPropsToCloudFormation (/Users/masonme/cdk-migration-test/node_modules/@aws-cdk/core/lib/cloudformation.generated.ts:1237:40)
    at CfnStack.renderProperties (/Users/masonme/cdk-migration-test/node_modules/@aws-cdk/core/lib/cloudformation.generated.ts:1367:16)
    at PostResolveToken.ret.Resources [as processor] (/Users/masonme/cdk-migration-test/node_modules/@aws-cdk/core/lib/cfn-resource.ts:324:40)
    at PostResolveToken.postProcess (/Users/masonme/cdk-migration-test/node_modules/@aws-cdk/core/lib/util.ts:92:17)
    at Object.postProcess (/Users/masonme/cdk-migration-test/node_modules/@aws-cdk/core/lib/private/resolve.ts:115:78)
    at DefaultTokenResolver.resolveToken (/Users/masonme/cdk-migration-test/node_modules/@aws-cdk/core/lib/resolvable.ts:149:32)
    at resolve (/Users/masonme/cdk-migration-test/node_modules/@aws-cdk/core/lib/private/resolve.ts:202:51)
    at Object.resolve (/Users/masonme/cdk-migration-test/node_modules/@aws-cdk/core/lib/private/resolve.ts:112:77)
    at resolve (/Users/masonme/cdk-migration-test/node_modules/@aws-cdk/core/lib/private/resolve.ts:220:47)
Subprocess exited with error 1

Environment

• CDK CLI Version : 1.103.0 (build bc13a66)
• Framework Version: Not sure what this means
• Node.js Version: v14.15.4
• OS : OSX 10.14.6
• Language (Version): TypeScript (Version 4.1.5)

Other

This may be related to #744, but I'm not sure.

---

This is 🐛 Bug Report

[skinny85]

Thanks for reporting @MasonHM, confirming I was able to reproduce the error. Working on a fix.

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