lambda.Function.addEnvironment appears to only accept string type values

[stevegoossens]

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• I'm submitting a ...

  • 🪲 bug report
  • 🚀 feature request
  • 📚 construct library gap
  • ☎️ security issue or vulnerability => Please see policy
  • ❓ support request => Please see note at the top of this template.

• What is the current behavior?
  If the current behavior is a 🪲bug🪲: Please provide the steps to reproduce

// fn is a lambda.Function
const tableTtl = 300;
fn.addEnvironment('TABLE_TTL', tableTtl)

attempting a cdk synth results in an error:

      throw new CfnSynthesisError(message);
            ^
Error: Resolution error: Supplied properties not correct for "CfnFunctionProps"
  environment: supplied properties not correct for "EnvironmentProperty"
    variables: element 'TABLE_TTL': 300 should be a string.

• What is the expected behavior (or behavior of feature suggested)?
  TABLE_TTL should be added as a Lambda environment variable as "300" (presumably Lambda env vars are only ever string type values)

• What is the motivation / use case for changing the behavior or adding this feature?
  I had to do the following as a workaround:

fn.addEnvironment('TABLE_TTL', tableTtl.toString())

the "hacky" string conversion is a bit (code-)smelly

• Please tell us about your environment:

  • CDK CLI Version: 1.0.0 (build d89592e)
  • Module Version: 1.0.0
  • OS: [ OSX High Sierra ]
  • Language: [ TypeScript ]

• Other information (e.g. detailed explanation, stacktraces, related issues, suggestions how to fix, links for us to have context, eg. associated pull-request, stackoverflow, gitter, etc)

I think .addEnvironment should handle the string conversion, as the value arg/param is documented as any type. I think a number to string conversion should be an easy quick fix, without having to necessarily cater for more difficult type to string conversions.

if (typeof value !== 'string') value = value.toString()

maybe that would be "good enough" to handle "any" (sane) values passed?

[nmussy]

Your issue is mentioned in #744

It's not really a construct library gap, but a fairly common CloudFormation quirk. It gets even more frustrating with ECS, in which you have the Container Cpu number property, and the Task Cpu string property. You end up with the following:

const cpuReservation = 256;
const memoryReservation = 256;

const taskDefinition = new TaskDefinition(this, 'task', {
    memoryMiB: memoryReservation.toString(),
    cpu: cpuReservation.toString(),
    compatibility: Compatibility.EC2,
});

const container = taskDefinition.addContainer('container', {
    logging: LogDriver.awsLogs({streamPrefix: 'ecs'}),
    image: ContainerImage.fromEcrRepository(ecr, 'latest'),
    cpu: cpuReservation,
    memoryLimitMiB: memoryReservation,
});

[stevegoossens]

My issue is that the AWS CDK documentation doesn't mention that the value type needs to be a string.

In https://docs.aws.amazon.com/cdk/api/latest/docs/@aws-cdk_aws-ecs.TaskDefinition.html, the cpu and memoryMIB properties/params are defined as string type.

Whereas, https://docs.aws.amazon.com/cdk/api/latest/docs/@aws-cdk_aws-lambda.Function.html#add-environmentkey-value, has the value as any type. Why bother documenting it in the AWS CDK documentation (i.e. not CloudFormation) that this value can be anything other than a string, when even a number fails?

Even easier suggested fix

If the AWS CDK documentation above was updated to value: string instead of value: any, that would be fine.

[nmussy]

I see, my bad. Your issue is that the environment property is defined as a map of any, while the CloudFormation Function Environment reference explicitly types it as Map of String:

aws-cdk/packages/@aws-cdk/aws-lambda/lib/function.ts

Line 79 in 305fed6

readonly environment?: { [key: string]: any };

[stevegoossens]

Yes, either the AWS CDK documentation (for the type of value) is wrong, or there is a missing type conversion (to string) in .addEnvironment

Going by the CDK docs, I wrongly assumed it would take care of any type conversions necessary.