(@aws-cdk/aws-lambda-nodejs): "error: Could not resolve" while bundling without Docker

I’m trying to bundle my Lambda using NodejsFunction but am failing. If I set forceDockerBundling to true (default is false), bundling (during cdk synth) is successful.

Reproduction Steps

    this.lambdaFunction = new lambdaNodeJs.NodejsFunction(this, 'MyLambda', {
      functionName: 'my-function',
      runtime: lambda.Runtime.NODEJS_12_X,
      memorySize: 256,
      depsLockFilePath: '../lambda',
      entry: '../lambda/build/index.js',
      handler: 'main',
      bundling: {
        externalModules: ['graphql'], // I found out this might be a problem due to an error I saw when forceDockerBundling was set to true
      },
      environment: {
        MY_FLAG: 'true',
      },
    });

For what it’s worth, my project is structured like:

├─ my-project
├── cdk
├── lambda

What did you expect to happen?

I expected the Lambda and (hopefully) its dependencies would be packaged using esbuild.

What actually happened?

$ cdk synth
Bundling asset FooStack/FooLambda/MyLambda/Code/Stage...
 > error: Could not resolve "../lambda/build/index.js"

1 error

Environment

• CDK CLI Version : 1.78.0
• Framework Version: 1.78.0
• Node.js Version: 12.20.0
• OS : macOS 10.15.7
• Language (Version): TypeScript 3.9.7

Other

I’ve tried setting the entry to a file that doesn’t exist, and I get a different error altogether. So I’m pretty sure that the file is being found, but some other problem is happening.

# cdk synth
Cannot find entry file at ../lambda/build/foo.js

---

This is 🐛 Bug Report

[jogold]

Also note that the idea of the NodejsFunction is that you don’t have to split your project between CDK and Lambda. Everything can live together and have a common package.json file. And you can point to a TS file.

[jogold]

I’m curious what the project organization would look like if I don’t split the project.

I recommend the approach described in https://github.com/aws/aws-cdk/blob/v1.78.0/packages/@aws-cdk/aws-lambda-nodejs/README.md#nodejs-function where your handler lives next to the file where the NodejsFunction is defined.

If everything lives together you can share utils and types between your infra code and Lambda code.

(also you don’t have to specify depsLockFilePath in this case, there’s only one lock file at the root of your repo and it will be detected)