(@aws-cdk/core): CfnMapping overview example throws Template format error: Mappings attribute name 'us-east-1' must contain only alphanumeric characters.

[gmedard]

link to reference doc page

https://docs.aws.amazon.com/cdk/api/latest/docs/core-readme.html#mappings

Describe your issue?

Attempting to define a region template mapping:

  const regionTable = new cdk.CfnMapping(this, "RegionTable", {
  mapping: {
    regionName: {
      "us-east-1": "value-one",
      "us-west-2": "value-two",
    },
  },
});

However, this is not working as documented. It's throwing this error:
"Template format error: Mappings attribute name 'us-east-1' must contain only alphanumeric characters."

[jumic]

The CloudFormation documentation describes this behavior:

The name can contain only alphanumeric characters (A-Za-z0-9).

After changing the structure of the mapping, the example can be deployed:

const regionTable = new cdk.CfnMapping(this, 'RegionTable', {
  mapping: {
    'us-east-1': {
      regionName: 'US East (N. Virginia)',
      // ...
    },
    'us-east-2': {
      regionName: 'US East (Ohio)',
      // ...
    },
    // ...
  }
});

regionTable.findInMap(cdk.Aws.REGION, 'regionName')

[gmedard]

Thank you for the response @jumic. That fix resulted in this new local error now:

"throw new Error(Mapping doesn't contain top-level key '${key1}');"

[jumic]

In which region are you deploying the stack? Did you maintain the mapping for your region (e.g. eu-west-1) in CfnMapping?

If I'm using my example with value eu-west-1, I get the same error. The log output also shows the specific value that is missing (see last line):

        throw new Error(`Mapping doesn't contain top-level key '${key1}'`);
              ^
Error: Mapping doesn't contain top-level key 'eu-west-1'

If this does not resolve your problem, could you please show me your code again?

[gmedard]

I was deploying in us-west-2 region and my code was as follows:

const regionTable = new cdk.CfnMapping(this, 'RegionTable', {
  mapping: {
    'us-east-1': {
      regionName: 'US East (N. Virginia)',
      // ...
    },
    'us-east-2': {
      regionName: 'US East (Ohio)',
      // ...
    },
    // ...
  }
});

regionTable.findInMap(cdk.Aws.REGION, 'regionName')

However, I have since figured out the way CDK will not make a fuss if I want to map the regions as the top key. The code that worked for me is below:

const regionMap = new cdk.CfnMapping(this, "RegionMap", {
  mapping: {
    ["us-east-1"]: {
      AMI: "ami-1234567e8f9example",
      SUBNETID: "subnet-ffffffff",
      SG: "sg-d9d9d9d9",
    },
    ["us-west-2"]: {
      AMI: "ami-1234567e6749example",
      SUBNETID: "subnet-eeeeeeee",
      SG: "sg-012345d7f90,
    },
  },
});

The synthesized mappings section of the template from above code is:

Mappings:
  RegionMap:
    us-east-1:
      AMI: ami-1234567e8f9example
      SUBNETID: subnet-ffffffff
      SG: sg-d9d9d9d9
    us-west-2:
      AMI: ami-1234567e6749example
      SUBNETID: subnet-eeeeeeee
      SG: sg-012345d7f90

The brackets seem to have solved the non alphanumeric original error.

[jumic]

In my example, I maintained the mapping only for regions us-east-1 and us-east-2. If you deploy it to region us-west-2, you have to maintain this value too. I think this was the reason for the error.

One additional question: Does your code work without squared brackets, too? I copied into my example project and I could deploy it without squared brackets.

I have created a pull request which updates the documentation. Therefore, it would be great to know if the squared brackets are mandatory in some cases.

[gmedard]

I had not tried without the brackets. I just deployed without them, and it worked. So it works with or without. Thanks much for the help on getting the documentation fixed.

[github-actions]

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