Multiple instances of CfnInclude cause TypeError

[scarybot]

Upon using cdk.CfnInclude multiple times, a TypeError is raised. The content or ordering of the templates doesn't appear to make a difference. Both the templates in the below example will synth correctly when used individually.

Reproduction Steps

import * as cdk from '@aws-cdk/core';
import * as fs from 'fs';
import * as YAML from 'yaml';

export class CdkStack extends cdk.Stack {
  constructor(scope: cdk.Construct, id: string, props?: cdk.StackProps) {
    super(scope, id, props);

    new cdk.CfnInclude(this, "Artifacts", {
      template: YAML.parse(
        fs.readFileSync("../test1.yml").toString()
      ),
    });

    new cdk.CfnInclude(this, "Buckets", {
      template: YAML.parse(
        fs.readFileSync("../test2.yml").toString()
      ),
    });
}

Error Log

/Users/jd/git/admin/build/cdk/node_modules/@aws-cdk/core/lib/stack.ts:988
        if (id in dest) {
              ^
TypeError: Cannot use 'in' operator to search for '0' in 2010-09-09
    at merge (/Users/jd/git/admin/build/cdk/node_modules/@aws-cdk/core/lib/stack.ts:988:15)
    at CdkStack._toCloudFormation (/Users/jd/git/admin/build/cdk/node_modules/@aws-cdk/core/lib/stack.ts:846:7)
    at CdkStack.synthesize (/Users/jd/git/admin/build/cdk/node_modules/@aws-cdk/core/lib/stack.ts:762:38)
    at CdkStack.onSynthesize (/Users/jd/git/admin/build/cdk/node_modules/@aws-cdk/core/lib/construct-compat.ts:123:10)
    at Node.synthesize (/Users/jd/git/admin/build/cdk/node_modules/constructs/lib/construct.ts:407:28)
    at Function.synth (/Users/jd/git/admin/build/cdk/node_modules/@aws-cdk/core/lib/construct-compat.ts:231:22)
    at App.synth (/Users/jd/git/admin/build/cdk/node_modules/@aws-cdk/core/lib/app.ts:142:36)
    at process.<anonymous> (/Users/jd/git/admin/build/cdk/node_modules/@aws-cdk/core/lib/app.ts:121:45)
    at Object.onceWrapper (events.js:428:26)
    at process.emit (events.js:321:20)
Subprocess exited with error 1

Environment

• CLI Version : 1.41.0 (build 9e071d2)
• Framework Version: uncertain
• OS : MacOS 10.15.1
• Language : English

Other

Contents of the test templates:

test1.yml:

---
AWSTemplateFormatVersion: "2010-09-09"
Description: Test 1

Resources:
  DummyResource:
    Type: AWS::CloudFormation::WaitConditionHandle

test2.yml:

---
AWSTemplateFormatVersion: "2010-09-09"
Description: Test 2

Resources:
  DummyResource:
    Type: AWS::CloudFormation::WaitConditionHandle

---

This is 🐛 Bug Report

[skinny85]

Thanks for opening the issue @scarybot . Confirming this is a bug on our side. Will work on a fix.

[skinny85]

BTW, you probably reduced the example to the minimum, but to be clear: your templates wouldn't work together anyway, because you use the same logical ID of DummyResource in both (our bug is somewhere else, but just to be clear 🤪).

[scarybot]

BTW, you probably reduced the example to the minimum, but to be clear: your templates wouldn't work together anyway, because you use the same logical ID of DummyResource in both (our bug is somewhere else, but just to be clear 🤪).

Thanks, yes, I was just trying to be illustrative :D