aws-lambda: Allow undefined values to be passed to the environment prop of a Function

[piotrekwitkowski]

Describe the bug

TypeScript doesn't allow me to pass objects with undefined props to the environment prop of a Lambda function.
This code could work but currently doesn't:

new Function(this, 'function', {
  environment: {
    myOptionalBucketName: thisBucketMayNotExist?.bucketName // <-- could work but doesn't 
  }
}

I would like to pass such object and let CDK deal with it.

Expected Behavior

TypeScript will not mark this as an error, my stack can be synthesized and deployed.

Current Behavior

I see a type error:

Type 'string | undefined' is not assignable to type 'string'.
  Type 'undefined' is not assignable to type 'string'.ts(2322)
function.d.ts(72, 14): The expected type comes from property 'environment' which is declared here on type 'FunctionProps'

Reproduction Steps

Can be reproduced with this code:

new Function(this, 'function', {
  code: Code.fromInline(''),
  handler: 'index.handler',
  runtime: Runtime.NODEJS_18_X,
  environment: {
    myOptionalBucketName: undefined
  }
}

Possible Solution

The type [key: string] : string specified in function.ts:L82 could be replaced with a Partial<[key: string] : string> (or a Partial<Record<string, string>>).

If needed, the passed values that are undefined should be filtered out before synth/deployment.

The workaround I need to have today is either conditionally append the prop in another statement or use a somewhat ugly conditional assignment with

{
  envVariable1: "aaa",
  ...(myLengthyBucketIdentifier?.bucketName && { myBucketName: myLengthyBucketIdentifier.bucketName })
}

Additional Information/Context

I'm opening this ticket to see if the maintainers see the current behavior as a bug or as a feature. I am able to implement the change/fix if approved.

CDK CLI Version

2.103.1

Node.js Version

18.12.1

OS

MacOS

Language

TypeScript

[khushail]

Hi @piotrekwitkowski , thanks for reaching out. Partial types are a JSII limitation and hence can't be supported.

[ashishdhingra]

Closing due to lack of traction.

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