(cloudformation-include): Incorrect rendering of Sub functions when using CfnInclude parameters

[daxAKAhackerman]

When importing a CloudFormation template using the CfnInclude class and specifying parameters with values that are the valueAsString property of instances of core CfnParameter, every instances of short sub functions (!Sub) are incorrectly translated. However, when the included template uses the long version of sub functions (Fn::Sub), the synthesized template is valid.

Reproduction Steps

topic.yml

AWSTemplateFormatVersion: "2010-09-09"

Parameters:
  Environment:
    Type: String

Resources:
  SNSTopic:
    Type: AWS::SNS::Topic
    Properties: 
      TopicName: !Sub my-sns-topic-${Environment}

short-sub-stack.ts

import * as cdk from '@aws-cdk/core';
import * as cfninc from '@aws-cdk/cloudformation-include'


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

    const environment = new cdk.CfnParameter(this, 'Environment', {
      type: 'String'
    })

    new cfninc.CfnInclude(this, 'UserPool', {
      templateFile: './lib/cfn-modules/topic.yml',
      parameters: {
        Environment: environment.valueAsString
      }
    })
  }
}

cdk synth --no-version-reporting --no-path-metadata --no-asset-metadata

What did you expect to happen?

The resulting template's sub functions should either be a valid short sub, or a valid long sub as such:

Fn::Sub:
  - my-sns-topic-${Environment}
  - Environment:
      Ref: Environment

What actually happened?

An invalid sub function is produced as such:

Fn::Sub:
  Fn::Join:
    - ""
    - - my-sns-topic-
      - Ref: Environment

Resulting in the following cfn-lint error: E1019: Sub should be a string or array of 2 items

And the following CloudFormation error when deployed: An error occurred (ValidationError) when calling the CreateChangeSet operation: Template error: One or more Fn::Sub intrinsic functions don't specify expected arguments. Specify a string as first argument, and an optional second argument to specify a mapping of values to replace in the string

Environment

• CDK CLI Version :1.97.0
• Framework Version:
• Node.js Version:v14.16.0
• OS : macOS Big Sur 11.2.3
• Language (Version):TypeScript (4.2.3)

Other

When using a long sub function, this issue does not happen and the produced cloudformation is valid. The following topic.yml file can be used to reproduce this behaviour:

AWSTemplateFormatVersion: "2010-09-09"

Parameters:
  Environment:
    Type: String

Resources:
  SNSTopic:
    Type: AWS::SNS::Topic
    Properties: 
      TopicName: 
        Fn::Sub: 
          - my-sns-topic-${Environment}
          - Environment: !Ref Environment

---

This is 🐛 Bug Report

[skinny85]

Thanks for the awesome bug report @daxAKAhackerman. Confirming I was able to reproduce it. Working on a fix.

[github-actions]

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