AWS Step Function JSONata how to combine input and result from task

When using JSONPath, I knew how to combine input to some task(for instance lambda) and just add the result to additional property. For instance:

{
 "input_1" : "value_1",
 "input_2" : "value_2
}

and after invoking lambda function, I would get(using ResultPath):

{
 "input_1" : "value_1",
 "input_2" : "value_2,
 "lambda_result" : "value_3"
}

How can I achieve this using JSONata?

With JSONata in Step Functions, the Output must contain all required properties explicitly. You can achieve this with a JSONata $merge:

{%
    $merge([$states.input, {
      "lambda_result": $states.result.Payload
    }])
%}