Is it possible to have a single parameter receive its value conditionally in a step function?

Question

I have a parameter 'request_id' that I want to have get an ID from two different formats of JSON that get sent to the input of my step function task.

The first form looks like this:

{ "request_id": "abcde-abcd-abcde-abc" }

The second is in this form:

{ "request": { "id": "abcde-abcd-abcde-abc", }

Currently, I have a parameter which looks like

"request_id.$": "$.request_id"

but would like something that is equivalent to (this one does not work)

"request_id.$": "$.['request_id','request.id']"

Is this possible within the step function or will I need to either split those two request id's up into two paths in my JSON or do it in a function?

Answer 1

One workaround could be to have a choice state and check if the first variable present or not:

{
    "Variable": "$.request_id",
    "IsPresent": true
}

And then two different assignment based on the result.

https://docs.aws.amazon.com/step-functions/latest/dg/amazon-states-language-choice-state.html

{
  "StartAt": "choice",
  "States": {
    "choice": {
      "Type": "Choice",
      "Choices": [
        {
          "Variable": "$.request_id",
          "IsPresent": true,
          "Next": "assignment1"
        }
      ],
      "Default": "assignment2"
    },
    "assignment1": {
      "Type": "Pass",
      "Result": "World",
      "End": true
    },
    "assignment2": {
      "Type": "Pass",
      "Result": "World",
      "End": true
    }
  }
}