[core] CfnMapping creates wrong mappings

[beomseoklee]

CfnMapping creates wrong CFN mappings. It should not add Mappings twice.

Please let me know if any other information is needed or I did something wrong.

Reproduction Steps

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

export class CDKStack extends cdk.Stack {
  constructor(scope: cdk.Construct, id: string, props?: cdk.StackProps) {
    super(scope, id, props);
    new cdk.CfnMapping(this, 'Mappings', {
      mapping: {
        Map: {
          This: {
            One: 'Yes'
          }
        }
      }
    });
  }
}

With that code, when I cdk synth --asset-metadata false --path-metadata false --version-reporting false --json true, it created wrong mappings.

What did you expect to happen?

{
  "Mappings": {
    "Map": {
      "This": {
        "One": "Yes"
      }
    }
  }
}

What actually happened?

{
  "Mappings": {
    "Mappings": {
      "Map": {
        "This": {
          "One": "Yes"
        }
      }
    }
  }
}

Environment

• CLI Version : 1.54.0
• Framework Version: 1.54.0
• Node.js Version: 12.13.1
• OS : OSX Mojave
• Language (Version): TypeScript (3.9.6)

---

This is 🐛 Bug Report

[eladb]

Each CfnMapping (singular) object represents a single entry in your template's Mappings section (plural). This way, you can define multiple mappings by simply creating multiple instances of CfnMapping.

The id of the CfnMapping construct will be used as the ID of the mapping.

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

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

    new cdk.CfnMapping(this, 'Map1', {
      mapping: {
        This: {
          One: 'Yes'
        }
      }
    });

    new cdk.CfnMapping(this, 'Map'2, {
      mapping: {
        Hello: 'world'
      }
    });
  }
}

Will yield:

{
  "Mappings": {
    "Map1": {
      "This": {
        "One": "Yes"
      }
    },
    "Map2": {
      "Hello": "World"
    }
  }
}

I've created a PR to update the docs to make it a bit clearer: #9451