Firebase Send Message to Multiple Topics

Question

I've been trying to send cloud messages to users who subscribed to multiple topics through an API call (POST https://fcm.googleapis.com/v1/projects/myproject-b5ae1/messages:send) with the following body:

{
  headers: {
    'Content-Type': 'application/json',
    'Authorization': `Bearer MY_ACCESS_TOKEN`
  },
  body: {
    "message": {
      "condition": "'cat' in topics || 'dog' in topics",
      "notification": {
        "title": "Message Title",
        "body": "Message Body" 
      }
    }
  }
}

I wrote this config according to the FCM documentation. I can get a response similar to this:

{
  "name": "projects/myproject-b5ae1/messages/5735743068807585451"
}

but no messages were received by any devices.

I've used the access token for other APIs, which works. I'm also aware that the FCM documentation also provided a different body for the cURL request, which I also tried but not working.

The weird thing is if I only provide one topic in the condition, a message is actually successfully sent to subscribed devices. Am I writing something wrong?

I've already referenced other solutions on Stackoverflow but everything is still not working:

Firebase API call with multiple topics in condition

How to send FCM Push Notifications to multiple topics

Answer 1

After talking to Firebase Support, they pointed out the problem I'm having here is a known bug they are still trying to fix. And there's no specific timeline for a fix yet.

Therefore, there's no problem with my code and I'll have to figure out a workaround myself if I really want to use the "||"(OR) operator.

My current workaround is keep track of subscribers with a database (since Firebase doesn't offer subscribers querying), then implement the OR condition myself by finding a union of subscribers to different topics.

P.S. I just don't get why the downvotes, I actually found a bug here and referenced all the solutions I could found on SO before asking the question here.