Arrays in v14 are now maps in v18?

[titanium-cranium]

Hi there:
We have been storing documents that contain attributes with arrays in firebase v14 for some time without issue. We have now upgraded to firebase v18 and we are now having issues persisting arrays. It seems as if in v14, when a key contained an array it stored it as an object with a set of numbered keys, but it still "knew" it was an array. You can see this in the firebase GUI by hovering over the key, it tells you the key contains either an (array) or a (map).

Is it possible to modify how the call to firebase persistence is configured to maintain the v14 data structure?

The code we use to persist our data structure looks like:

    this.collectionRef()
      .doc(id)
      .set(data as FirebaseFirestoreTypes.DocumentData)

Example Data Structure

{
   key: "foo",
   data: [
            {
               arr: ["a", "b", "c"]
            },
            {
               arr: ["a", "b", "c"]
            }
           ]
}

is persisted as

{
    key: "foo",
    data: [                   <== array in v14 & v18**
               {
                arr: {           <== array in v14, but map in v18**
                           0: "a",
                           1: "b",
                           2: "c"
                        }
            },
               {
                arr: {           <== array in v14, but map in v18**
                           0: "a",
                           1: "b",
                           2: "c"
                        }
            },
          ]
}
         

[titanium-cranium]

After digging around it turns out the firebaseSDK updated from v14 to v15 to convert all nested arrays to maps.