(sns): fifo topic construct doesn't append .fifo to the topic name

The SNS FIFO topics are failing to deploy because the topic name is missing .fifo at the end.

Reproduction Steps

Create a minimal cdk app with the following SNS FIFO topic and deploy it:

import * as sns from "@aws-cdk/aws-sns";
import * as cdk from "@aws-cdk/core";

class MyStack extends cdk.Stack {
  constructor(scope: cdk.Construct, id: string, properties?: cdk.StackProps) {
    super(scope, id, properties);

    new sns.Topic(this, "MyTopic", {
      fifo: true,
    });
  }
}

const app = new cdk.App();

new MyStack(app, "MyStack");

What did you expect to happen?

The SNS topic should append .fifo to the topic name if topic: true and .fifo is not present already.

What actually happened?

The deploy failed:

9:48:48 PM | CREATE_FAILED        | AWS::SNS::Topic                 | FanOutTopic
Invalid parameter: Topic Name (Service: AmazonSNS; Status Code: 400; Error Code: InvalidParameter; Request ID: xxxxx-xxxx-xxxx-xxxxx; Proxy: null)

Environment

• CDK CLI Version : v1.83.0
• Framework Version: v1.83.0
• Node.js Version: v12.20.0
• OS : Ubuntu 20
• Language (Version): TypeScript (4.1)

Other

It works if you manually set the topicName to include .fifo at the end, like this:

new sns.Topic(this, "MyTopic", {
    fifo: true,
    topicName: "MyTopic.fifo",
});

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This is 🐛 Bug Report

[rrhodes]

Agreed, that sounds like a good step forward until the underlying problem is resolved. Happy to open a PR for this. The underlying bug is already documented in the CloudFormation roadmap

[NetaNir]

So currently the API is broken, if a name is not passed- the queue creation will fail. And if a name is passed but does not have the .fifo suffix - the queue creation will fail.

This is not a great customer experience and we should make it better, the minimum is to throw an error if fifo is set to true and queueName is not passed or missing the .fifo. Build time errors are always better than deploy time error.

The better experience will be to append the fifo suffix if a name is passed and to throw if a name is not passed.