Type-safe stack outputs in AWS CDK

In order to ensure that the outputs of your CloudFormation Stacks are typed properly, you can use this technique.

When defining the outputs, use a helper function that is bound to a type that defines all stack outputs. This ensures that outputs that are created are defined in the type definition.

/**
 * This defines the outputs the stack creates
 */
export type StackOutputs = {
  bucketName: string;
};

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

    /**
     * A helper function that only allows
     * to create outputs that are defined in `StackOutputs`
     */
    const output = (name: keyof StackOutputs, value: string) =>
      new CfnOutput(this, name, {
        value,
      });

    const bucket = new Bucket(this, "bucket");
    output("bucketName", bucket.bucketName);
  }
}

This enables to use the type that defines the outputs when querying CloudFormation for the stack outputs.
In the example below we use @nordicsemiconductor/cloudformation-helpers, which simplifies fetching stack outputs and accepts a type for defining which outputs the stack returns. This will make outputs properly typed.

const cf = new CloudFormationClient({});

const outputs = await stackOutput(cf)<StackOutputs>("MyStack");

console.log("Bucket name:", outputs.bucketName);

Run the example

npm ci

npx cdk deploy
# MyStack
# Deployment time: 38.5s
#
# Outputs:
# MyStack.bucketName = mystack-bucket43879c71-1prqx9wocdsp7

npx tsx use-stack-outputs.ts
# Bucket name mystack-bucket43879c71-1prqx9wocdsp7