Cannot Delete Retained MQTT Messages Anymore

[PeterBurner]

Checkboxes for prior research

• I've gone through Developer Guide and API reference
• I've checked AWS Forums and StackOverflow.
• I've searched for previous similar issues and didn't find any solution.

Describe the bug

We are using the NodeJS package @aws-sdk/client-iot-data-plane to interact with AWS IoT Core. Since the update from v3.928.0 to v3.929.0 we can no longer delete retained messages. We usually send undefined in the payload of the PublishCommand. However with the new SDK version the topic is actually set to an empty object ({}) instead of being deleted. We also tried sending null or empty string ''. Always with the same result.

Regression Issue

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

SDK version number

@aws-sdk/client-iot-data-plane@3.928.0 --> @aws-sdk/client-iot-data-plane@3.929.0

Which JavaScript Runtime is this issue in?

Node.js

Details of the browser/Node.js/ReactNative version

v22.18.0

Reproduction Steps

1. Publish a payload to an MQTT topic.
2. Publish undefined to the same MQTT topic.
3. Check whether retained topic still exists. --> Should result in ResourceNotFoundException

import {
  GetRetainedMessageCommand,
  IoTDataPlaneClient,
  PublishCommand
} from '@aws-sdk/client-iot-data-plane';

const client = new IoTDataPlaneClient({
  region: 'eu-central-1'
});

await client.send(
  new PublishCommand({
    payload: JSON.stringify({
      test: 'data'
    }),
    retain: true,
    topic: 'test'
  })
);

console.log(
  'topic exists:',
  await client
    .send(
      new GetRetainedMessageCommand({
        topic: 'test'
      })
    )
    .then(() => true)
    .catch(() => false)
);

await client.send(
  new PublishCommand({
    payload: undefined,
    retain: true,
    topic: 'test'
  })
);

console.log(
  'topic exists:',
  await client
    .send(
      new GetRetainedMessageCommand({
        topic: 'test'
      })
    )
    .then(() => true)
    .catch(() => false)
);

Observed Behavior

Retained topic is not being deleted.

Expected Behavior

Retained topic should have been deleted.

Possible Solution

No response

Additional Information/Context

No response

[kuhe]

Hi. Thanks for reporting this and sorry I didn't catch it.

As a workaround, please try using an empty byte payload: new Uint8Array(), or earlier version of the client.

await client.send(
  new PublishCommand({
    payload: new Uint8Array(0),
    retain: true,
    topic: 'test'
  })
);

This field is technically a byte payload rather than a string one, but we'll get a patch released as as soon as possible later today.

[kuhe]

A patch was released as part of https://github.com/aws/aws-sdk-js-v3/releases/tag/v3.931.0.

In this version, you can now continue to delete retained messages with a payload value of "" empty string, null, undefined, or new Uint8Array() empty byte array.

In v3.929.0 and v3.930.0, use an empty byte array new Uint8Array().