Payload error in Cloud Functions for Firebase Messaging

Question

I wrote a cloud function using Cloud Functions for Firebase that sends notifications to certain topics of Firebase Messaging. The final parts of the function define the payload to be sent, then sends it:

// javascript code in cloud functions
const payload = {
      'notification': {
        'title': `${toTitleCase(name)} just logged an event`,
        'body': `${events[eventType]} for ${toTitleCase(petName)}`,
        'data': {
            'personSent': userSent 
        }
      }
    };
console.log(payload);
admin.messaging().sendToTopic(pet_Id, payload);

However, I'm getting the error log in my Firebase console:

Error: Messaging payload contains an invalid value for the "notification.data" property. Values must be strings.

When I logout the payload I confirmed it is all strings:

{ notification: 
   { title: 'Turtle Dude just logged an event',
     body: 'Walk for Beer',
     data: { personSent: 'mfsP8U0qDdQL4rrrbXp6K0YsF423' } } }

However, when I send the same payload from my iPhone app (which I'm trying to avoid since that means I have to store the messaging private key on the client side) I am able to attach the extra data I want to send just fine:

// Swift code in iPhone app
let body: [String: Any] = ["to": "/topics/\(currentPet)",
                            "priority" : "high",
                            "notification" : [
                                "body" : "\(events[eventType]) for \(petsName.localizedCapitalized)",
                                "title" : "\(myName.localizedCapitalized) just logged an event",
                                "data" : ["personSent": myId]
                              ]
                           ]

How can I accomplish adding additional data in my cloud function like I do in my Swift code?

Answer 1

As others explained in the comments, the data object should go inside payload,
NOT inside notification.

Try the following code:

// javascript code in cloud functions
const payload = {
      'notification': {
        'title': `${toTitleCase(name)} just logged an event`,
        'body': `${events[eventType]} for ${toTitleCase(petName)}`,
      }, 
      // NOTE: The 'data' object is inside payload, not inside notification
      'data': { 
            'personSent': userSent 
      }
    };
console.log(payload);
admin.messaging().sendToTopic(pet_Id, payload);