Sharing Typescript code between AWS Lambda with AWS SAM CLI

Introduction

Recently, Amazon has released a beta version of AWS SAM CLI with the support of Typescript.
The sample works well when you have a simple use case.
Now, imagine that you want to have multiple AWS Lambda in your repository and have to share your code.
The goal of this post is to continue using SAM CLI to build and deploy your Typescript code.

Default configuration

By default, you can notice that the CodeUri property is referencing only your function folder.

HelloWorldFunction:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: hello-world/
      Handler: app.lambdaHandler
      Runtime: nodejs16.x

and your code is like the following:

import type { APIGatewayProxyEvent, APIGatewayProxyResult } from 'aws-lambda';
import { helloWorld } from '../shared/hello';

export const lambdaHandler = async (event: APIGatewayProxyEvent): Promise<APIGatewayProxyResult> => {
    return {
        statusCode: 200,
        body: JSON.stringify({
            message: helloWorld,
        }),
    };
};

When you'll try to build with an import that is not part of the current directory you'll get the following error:

Build Failed
Error: NodejsNpmEsbuildBuilder:EsbuildBundle - Esbuild Failed: ✘ [ERROR] Could not resolve "../shared/hello"

app.ts:2:27:
2 │ import { helloWorld } from '../shared/hello';

Custom configuration

You need to change the CodeUri property to a folder that contains all the source files that you want to share.

  HelloWorldFunction:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: .
      Handler: app.lambdaHandler

Thanks to this configuration you can now share your code between multiple AWS Lambda.

By default, AWS SAM CLI is using bundling, tree shaking, and minification so the code that is not called in your AWS Lambda will not be deployed.

You can look at the code directly on this sample: https://github.com/faridz974/sam-typescript

Conclusion

AWS SAM CLI with the support of Typescript is still in Beta. If you want more advanced features maybe you should not use it.
Lately, in version 1.49.0 External and Loader properties have been added.
If you want to share your feedback and/or requests this issue has been created.