How to extend AWS EventBridge event with new field or override existing field

Question

I have an integration between AWS EventBridge and AWS Lambda. I'm using aws-cdk to create Rule.

Let's say I have EB event in the following format

{
  "event": {
    "version": "0",
    "id": "e7e4d675-1bea-ad19-ffa3-4d6e962e15af",
    "detail-type": "SOMETHING_HAPPENED",
    "source": "source",
    "account": "111111111111",
    "time": "2023-02-23T14:52:34Z",
    "region": "eu-west-1",
    "resources": [],
    "detail": {
      "data": { "key": "value" },
      "metadata": { "correlation-id": "some uuid" }
    }
  }
}

In my AWS lambda, as an input, I want to omit metadata and set details = nested data but keep other fields

{
  "event": {
    "version": "0",
    "id": "e7e4d675-1bea-ad19-ffa3-4d6e962e15af",
    "detail-type": "SOMETHING_HAPPENED",
    "source": "source",
    "account": "111111111111",
    "time": "2023-02-23T14:52:34Z",
    "region": "eu-west-1",
    "resources": [],
    "detail": { "key": "value" }
  }
}

The documentation lacks of examples or hidden somewhere.

Is it possible to enrich or replace subset of fields of the original event?

Answer 1

EventBridge Input Transformation is the feature for you.
It does exactly what you need: transforming an event input before it's passed to the consumer.
You can configure it from CloudFormation / Terraform or from the Console UI, in the step "Configure Target" (third step), under the "Additional Settings" -> "Configure target input" section.

Based on your question, your Input Transformer configuration should be something like:

{
  "version" : "$.version",
  "id" : "$.id",
  ...and so on... 
  "detail": "$.detail.data"
}