Setting `error` with `stub_responses` in `aws-sdk-states` doesn't work

[jordan-brough]

Describe the bug

Setting an error when using stub_responses doesn't seem to work with describe_execution in Aws::States.

Example:

client = Aws::States::Client.new(stub_responses: true)
client.stub_responses(
 :describe_execution,
 {
   execution_arn: "arn:aws:states:us-east-1:123456789012:execution:TestStateMachine:execution-id",
   status: "FAILED",
   cause: "example cause",
   error: "example error",
   state_machine_arn: "arn:aws:states:us-east-1:123456789012",
   start_date: Time.now,
 },
)
result = client.describe_execution(execution_arn: "arn:aws:states:us-east-1:123456789012:execution:TestStateMachine:execution-id")

result.status
=> "FAILED"

result.cause
=> "example cause"

result.error
=> nil # 👈 I expected this to be "example error" 👈

Regression Issue

• Select this option if this issue appears to be a regression.

Expected Behavior

See above code example.

Current Behavior

See above code example.

Reproduction Steps

See above code example.

Possible Solution

No response

Additional Information/Context

No response

Gem name ('aws-sdk', 'aws-sdk-resources' or service gems like 'aws-sdk-s3') and its version

aws-sdk-states

Environment details (Version of Ruby, OS environment)

Ruby 3.3.6, macOS 15.7, aws-sdk-states 1.97.0, aws-sdk-core 3.233.0

[mullermp]

This is an edge case with response data delegation. resposne.error will be raised on service errors, for which none exists here, so that is why it's nil. Try calling response.data.error.

[jordan-brough]

Got it, thanks. So it's not just with stub_responses that this happens, it's in real production usage as well.

Is there a note anywhere in the Ruby docs about that edge case? Would be nice to have one if not 🙏
E.g. the docs on rubydoc.info suggest .error will work:

---

The workaround of calling response.data.error does seem to work. Thank you! 🎉

[mullermp]

Yes. It's an issue with delegation. Response objects inherit from Delegator and delegate to data. When you call response.status, it's implicitly calling response.data.status. Because Response has an error method, it overwrites the delegation.