How to easily develop and deploy TypeScript Lambda functions

Introducing CDK TypeScript resource

Why?

All-TypeScript codebase including infrastructure as a code with CDK and application code is a pleasure to use.
Deployment of it, not so much.

You can transpile your code to a new directory, copy package.json there, install production dependencies, and then have CDK send that whole folder to lambda. It's painful to set up, and it will bring a ton of unnecessary code (everything in node_modules) along.
Webpack is better - it can take an entry point and create a small bundled file that includes only what you need.
Unfortunately, no one likes to set up complex and diverging webpack configurations, especially in a monorepo with tens if not hundreds of tiny packages.

What?

We wanted the TypeScript Lambda experience to be seamless - if a developer wants to create a new function, he should create a typescript file, add it to CDK and that's it. Now you can do it like so:

import { TypeScriptFunction } from "cdk-typescript-tooling";
// ...
const statusHandle = new TypeScriptFunction(scope, "Purchase-Status-Endpoint", {
  entry: require.resolve("@sales/purchase-endpoint/src/handler.ts"),
});

It takes all the parameters that you know from @aws-cdk/aws-lambda, like runtime, environment, timeout, and so on, because we extend it.

Expose easily through HTTP

Why?

In our development exposing lambdas through http is a very frequent case. The code around it for most cases stays exactly the same and increases the noise.
We define the function:

const handler = new TypeScriptFunction(stack, "Add-Function", {
  entry: require.resolve("@calculator/add/src/handler.ts"),
});

Add HttpApi using LambdaProxyIntegration

const statusApi = new apiGateway2.HttpApi(stack, "PurchaseStatusHttpApi", {
  defaultIntegration: new apiGateway2Integrations.LambdaProxyIntegration({
    handler,
  }),
});

Add the url to CfnOutput to, among others, see the url in CI/CD logs.

new CfnOutput(stack, "addUrl", {
  value: statusApi.url,
});

What?

Define your function with withHttp option like so:

new TypeScriptFunction(stack, "Add-Function", {
  entry: require.resolve("@calculator/add/src/handler.ts"),
  withHttp: true,
});

...and the other two steps will be done for you automatically.

You can watch me build an example using the TypeScriptFunction from cdk-typescript-tooling here:

The code source created while recording that video is here

The package is available here

Let me know if you have any questions or thoughts in the comments below.

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