Document that @app.on_topic() cannot be used for topics that have dedicated decorators

[janekbettinger]

The callbacks registered by the on_topic() decorator are currently processed last.
See

rhasspy-hermes-app/rhasspyhermes_app/__init__.py

Line 241 in 3ea35f4

else:

If a message on a topic for which a corresponding decorator exists (e.g. the on_intent decorator for the topic hermes/intent/<intent_name>) the topic callback is not executed at all.

Example:

@app.on_topic("hermes/intent/myIntent")
async def topic_callback(intent: NluIntent):
    # do something
    pass

The topic_callback is never called as

rhasspy-hermes-app/rhasspyhermes_app/__init__.py

Line 205 in 3ea35f4

elif NluIntent.is_topic(topic):

matches first. In this case the intended callback topic_callback won't be found as it is not included in the _callbacks_intent but only in the _callbacks_topic dictionary.

This can be considered an expected behavior, but is not intuitive nevertheless, imho. Please document this limitation at least.

It would be even better, to change the overall behavior to allow subscribing to arbitrary topics with the on_topic decorator. This would even allow subscriptions for multiple intents as requested in #13 via @app.on_topic("hermes/intent/+"). Some rework of the overall message processing would be required though.