kafka_topic: invalid check_mode behaviour when updating an existing topic

[saiello]

Expected Behavior

Running kafka_topic module in check mode, to update a topic, should reflect actual behaviour and report potential changes.

Actual Behavior

Running in check mode reports " Nothing to do", however removing the --check option perform the updates.

Ad-hoc commands to Reproduce the Problem

1. Create a topic

   ansible -m kafka_topic localhost -a 'bootstrap_servers=localhost:9092 name=sample-topic partitions=3 replica_factor=1 state=present'

localhost | CHANGED => {
    "changed": true,
    "changes": {
        "topic_created": [
            {
                "force_reassign": false,
                "name": "sample-topic",
                "options": {},
                "partitions": 3,
                "preserve_leader": false,
                "replica_factor": 1,
                "state": "present"
            }
        ]
    },
    "msg": "topic sample-topic successfully created. "
}

2. Check for topic options update

ansible -m kafka_topic localhost -a 'bootstrap_servers=localhost:9092 name=sample-topic partitions=3 replica_factor=1 options={{ options }}' -e '{"options": { "retention.ms": 100000}}' --check 

localhost | SUCCESS => {
    "changed": false,
    "changes": {},
    "msg": "nothing to do."
}

3. Execute topic's options update

ansible -m kafka_topic localhost -a 'bootstrap_servers=localhost:9092 name=sample-topic partitions=3 replica_factor=1 options={{ options }}' -e '{"options": { "retention.ms": 100000}}'

localhost | CHANGED => {
    "changed": true,
    "changes": {
        "topic_updated": [
            "sample-topic"
        ]
    },
    "msg": "topic sample-topic successfully updated. "
}

[saiello]

The problem might be in the implementation of these lines:

        // module_utils/kafka_lib_topic.py   [63-74]

        if len(topics_to_maybe_update) > 0:
            if not module.check_mode:
                topics_changed, warn = manager.ensure_topics(
                    topics_to_maybe_update
                )
                changed = len(topics_changed) > 0
                if changed:
                    msg += ''.join(['topic %s successfully updated. ' %
                                    topic for topic in topics_changed])
                    changes.update({
                        'topic_updated': topics_changed
                    })

[saiello]

I've realized the issue might be resolved in #103. I will check it