Using boolean variable in Serverless (TypeScript) config

Question

I’m trying to use a boolean variable in a Typescript serverless config, but I can’t seem to get the syntax right.

From the docs, I think I’m supposed to be using strToBool() but I don’t seem to be able to create a parseable TypeScript file.

Is my syntax wrong, or am I just going about this all wrong?

tracing: {
  apiGateway: ${strToBool(${self:custom.AwsXRayEnabled.${opt:stage})},
},

Answer 1

strToBool() only solves the problem that when a boolean value is received from a variable like e.g. SSM is actually returned as a String. strToBool will then make the conversion. But if your custom variable custom.AwsXRayEnabled.${opt:stage} has a hardcoded boolean value like following:

{
  custom:
    AwsXRayEnabled:
      prod: false
}

then strToBool is not necessary.

Your "issue" is actually Typescript, as my guess is that your compiler says something like:

Type 'string' is not assignable to type 'boolean'

And in a sense that is correct, because you do have string defined with:

tracing: {
  apiGateway: "${self:custom.AwsXRayEnabled.${opt:stage})",
},

What Typescript doesn't know is that this "string" will be substituted by the Serverless framework templating engine to a boolean value.

So the solution is to tell Typescript that it will be a Boolean. This can be achieved by simply doing:

tracing: {
  apiGateway: "${self:custom.AwsXRayEnabled.${opt:stage})" as unknown as boolean,
},

Why do you first need to set unknown? Well I'm not a Typescript expert but Phpstorm does give an interesting explanation:

TS2352: Conversion of type 'string' to type 'boolean' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.