CODEWITHSUNDEEP
amazon-web-servicesstate-machineaws-step-functionsjsonata
datahack
datahack

Reputation: 691

Step Functions JSONata MapIterator Bug

When I have this input

{
  "input": {
    "bucket_name": "ml-platform-qa-us-east-1",
    "object_keys": [
      {
        "Key": "aws/lambda/5e7faac5-052a-4ac2-a032-2c1ad3a28459/shardId-000000000002/2024/11/29/",
        "Size": 0
      },
      {
        "Key": "aws/lambda/5e7faac5-052a-4ac2-a032-2c1ad3a28459/shardId-000000000002/2024/11/29/2024-11-29T15.57.25-16468255-9704-44d9-93b6-c2c256daa914",
        "Size": 178665
      }
    ]
  },
  "inputDetails": {
    "truncated": false
  },
  "name": "Map: Iterate over failed events"
}

and using MapIterator with following line:

"Items": "{% $states.input.object_keys[Size>0].Key %}"

I get an error:

An error occurred while executing the state 'Map: Iterate over failed events' (entered at the event id #14). The JSONata expression '$states.input.object_keys[Size>0].Key' specified for the field 'Items' returned an unexpected result type. Expected 'array', but was 'string' for value: \"aws/lambda/5e7faac5-052a-4ac2-a032-2c1ad3a28459/shardId-000000000002/2024/11/29/2024-11-29T15.57.25-16468255-9704-44d9-93b6-c2c256daa914\"

If I add one more key with size greater then 0, then I get array of two items and everything is fine. Why I do not get ["aws/lambda/5e7faac5-052a-4ac2-a032-2c1ad3a28459/shardId-000000000002/2024/11/29/2024-11-29T15.57.25-16468255-9704-44d9-93b6-c2c256daa914"] instead list is transformed to string? It looks like a bug.

Upvotes: 1

Views: 238

Answers (1)

Vlad Dimov
Vlad Dimov

Reputation: 131

To make the JSONata expression always return an array, you need to add square brackets somewhere in the path, like so:

"Items": "{% $states.input.object_keys[Size>0].Key[] %}"

Link to JSONata playground: https://jsonatastudio.com/playground/f789749e

Upvotes: 0

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