States.Runtime error when nested step function fails in Step Functions Local

Question

AWS Step Functions Local does not handle a failure in a nested step function correctly. What is the best place to report a bug? Is this forum a good place for this - or is an issue tracker available somewhere?

The issue happens if we have nested step functions: e.g. an inner step function that is invoked by the outer one. If the inner step function fails (e.g. via a `Fail` state), the outer step function incorrectly tries to parse the step function Output (which is `null` due to failure) and itself fails with `States.Runtime` error and `argument "content" is null` cause).

To reproduce, use the latest amazon/aws-stepfunctions-local:1.10.1 Docker image. Launch the container with the following command (note the `STEP_FUNCTIONS_ENDPOINT` pointing to itself to enable nested step function execution:
```
docker run -p 8083:8083 -e STEP_FUNCTIONS_ENDPOINT=http://localhost:8083 amazon/aws-stepfunctions-local
```

Then create a simple HelloWorld inner step function in the Step Functions Local container with a single `Fail` state:

```
aws stepfunctions --endpoint-url http://localhost:8083 create-state-machine --definition "{\
    \"StartAt\": \"HelloFail\",\
    \"States\": {\
        \"HelloFail\": {\
        \"Type\": \"Fail\",\
        \"Error\": \"TestFailure\",\
        \"Cause\": \"Test cause\"\
        }\
    }}" --name "HelloWorld" --role-arn "arn:aws:iam::012345678901:role/DummyRole"
```

Add a simple outer step function that executes the HelloWorld one:

```
aws stepfunctions --endpoint-url http://localhost:8083 create-state-machine --definition "{\
\"StartAt\": \"InnerInvoke\",\
\"States\": {\
    \"InnerInvoke\": {\
    \"Type\": \"Task\",\
    \"Resource\": \"arn:aws:states:::states:startExecution.sync:2\",\
    \"Parameters\": {\
        \"StateMachineArn\": \"arn:aws:states:us-east-1:123456789012:stateMachine:HelloWorld\"\
    },\
    \"End\": true\
    }\
}}" --name "HelloWorldOuter" --role-arn "arn:aws:iam::012345678901:role/DummyRole"
```

Finally, start execution of the outer Step Function:

```
aws stepfunctions --endpoint-url http://localhost:8083 start-execution --state-machine-arn arn:aws:states:us-east-1:123456789012:stateMachine:HelloWorldOuter
```

The execution fails with the `argument "content" is null` error in the logs:

```
arn:aws:states:us-east-1:123456789012:execution:HelloWorldOuter:720b9e13-efdc-4718-9a70-be3eab15f416 : {"Type":"ExecutionFailed","PreviousEventId":2,"ExecutionFailedEventDetails":{"Error":"States.Runtime","Cause":"argument \"content\" is null"}}
```

Debugging the stepfunction-local Java application, I was able to narrow the error down to JSON parsing failing in `DescribeExecutionJson` class:
```
resultNode.set("Output", this.mapper.readTree(executionResult.getOutput()));
```

The problem is that `getOutput()` is `null` for a `FAILED` step function execution `DescribeExecution` response. So this seems to be a bug - would like to get it to the Step Function Local developers to fix.

Answer

Hi, I am running into the same problem. On running get-execution-history, I see the error: "The security token included in the request is invalid. (Service: AWSStepFunctions; Status Code: 400; Error Code: UnrecognizedClientException; Request ID: 5bd913be-1bac-4d90-9970-994d9a0a9f8c; Proxy: null)". I followed https://docs.aws.amazon.com/step-functions/latest/dg/sfn-local-config-options.html for adding fake credentials for my local development, but no success.

States.Runtime error when nested step function fails in Step Functions Local

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