firebase-ios-sdk: Firestore Data Bundles doesn't support empty Array and empty Map

My environment

• Xcode version: 13.2.1
• Firebase SDK version: 8.12.1
• Installation method: CocoaPods
• Firebase Component: Firestore
• Target platform(s): iOS

Problem

Steps to reproduce:

Context

To reduce firestore cost, I’m trying to use Firestore Data Bundles for my project.

Steps

1. [Cloud Function] Get my-home-users firestore query snapshot by using Firebase Admin SDK and bundle them into txt file.
2. [Cloud Function] Upload the bundle txt file to GCS.
3. [iOS] Load the bundle txt file from GCS.

When I create bundle txt file with firestore query snapshot data which doesn’t include multi bytes string data I can get namedQuery in Swift.

However if I try to create bundle txt file which includes multi bytes string data like Japanese I failed to get it.

Relevant Code:

Cloud Functions

bundleHomeNewUsers.ts

import { getAdmin } from "../../util/firebase";
import * as firebase from "firebase-admin";
import * as fs from "fs";

export const bundleHomeNewUsers = async () => {
  const BUCKET_NAME = "my-project-firestore-data-bundles";
  const admin = getAdmin();
  const db = admin.firestore();

  const bundle = db.bundle("home-users");
  const querySnapshot = await db
    .collection("users")
    .orderBy("createAt", "desc")
    .limit(4)
    .get();
  const buffer = bundle.add("home-users-bundles-query", querySnapshot).build();

  //Create tmp local file to upload
  const bundledFilePath = `/tmp/bundle.txt`;
  const charset = "utf8";
  fs.writeFileSync(bundledFilePath, buffer, charset);

  //Upload bundle file to Storage
  const destination = `firestore-data-bundles/home_users_bundles.txt`;
  await firebase
    .storage()
    .bucket(BUCKET_NAME)
    .upload(bundledFilePath, {
      destination,
      public: true,
      metadata: {
        cacheControl: `public, max-age=60`,
        contentType: "text/plain; charset=utf8",
      },
    });
  console.log(
    `Uploaded to https://storage.googleapis.com/${BUCKET_NAME}/${destination}`
  );
};

Swift

FirestoreService.swift

let db = Firestore.firestore()
      let urlString = "https://storage.googleapis.com/nadare-production-firestore-data-bundles/firestore-data-bundles/home_users_bundles.txt"

guard let url = URL(string: urlString),
let bundle = try? String(contentsOf: url, encoding: .utf8) else {
              print("[DEBUG] loadHomeUsers: Not found bundle file")
              return
            }

      db.loadBundle(Data(bundle.utf8)) { progress, error in
        switch progress?.state {
        case .success:
          print("[DEBUG] success")
          db.getQuery(named: "home-users-bundles-query") { query in
            guard let query = query else {
              print("[DEBUG] Failed to get named query")
              return
            }
            print("[DEBUG] Succeeded to get query🎉🎉🎉")

            query.getDocuments(source: .cache) { snapshot, error in
              if let error = error {
                return
              }
              guard let snapshot = snapshot else {
                return
              }
              observer.sendCompleted()
            }
          }

        case .inProgress:
          print("[DEBUG] inProgress case")
        case .error:
          print("[DEBUG] error case: \(error.debugDescription)")

        default:
          print("[DEBUG] default case")
        }
      }

Output

[DEBUG] Failed to get named query

Firebase SDK error log

Error Domain=FIRFirestoreErrorDomain Code=2 "Loading bundle failed with unknown error" UserInfo={NSLocalizedDescription=Loading bundle failed with unknown error})
8.12.1 - [Firebase/Firestore][I-FST000001] Failed to GetNextElement() from bundle with error 'values' is missing or is not an array
8.12.1 - [Firebase/Firestore][I-FST000001] Progress set to Error, but error_status() is ok()