JsonCacheInfoRepository: FormatException: Unexpected end of input (at character 1) ^

Open Beginner friendly
#450 9 comments 8 reactions 0 assignees View on GitHub

Nobody has claimed this yet.

Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
68/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Quiet
Tech stack
dart, flutter
Domain
mobile

Research direction

Start in json_cache_info_repository.dart at JsonCacheInfoRepository._readFile, around line 143, and inspect how an empty database JSON file reaches jsonDecode. Reproduce or cover the empty-file case, then verify initialization completes without a FormatException while preserving normal JSON loading.

Written by the indexing model from the issue text.

Description

🐛 Bug Report

occasionally this error is generated when initializing CacheManager with JsonCacheInfoRepository

Fatal Exception: io.flutter.plugins.firebase.crashlytics.FlutterError: FormatException: Unexpected end of input (at character 1)

^

       at .jsonDecode(dart:convert)
       at JsonCacheInfoRepository._readFile(json_cache_info_repository.dart:143)
       at JsonCacheInfoRepository.open(json_cache_info_repository.dart:40)
       at new CacheStore.<fn>(cache_store.dart:34)

This happens when the {databaseName}.json file is created but empty and jsonString = ""

JsonCacheInfoRepository.dart: _readFile()
final json = jsonDecode(jsonString) as List<dynamic>;

A possible solution would be to check that the file is not empty before decoding the json

    if (await file.exists() && await file.length() > 0) {
      try {
        final jsonString = await file.readAsString();
        final json = jsonDecode(jsonString) as List<dynamic>;

note: I don't know why the json file is empty and not with an empty list []

Expected behavior

no error

Configuration

Doctor summary (to see all details, run flutter doctor -v):
[√] Flutter (Channel stable, 3.16.1, on Microsoft Windows [Versi¢n 10.0.22631.3296], locale es-CL)
[√] Windows Version (Installed version of Windows is version 10 or higher)
[√] Android toolchain - develop for Android devices (Android SDK version 34.0.0)
[√] Chrome - develop for the web
[√] Visual Studio - develop Windows apps (Visual Studio Build Tools 2022 17.8.2)
[√] Android Studio (version 2022.3)
[√] VS Code (version 1.87.2)
[√] Connected device (4 available)
[√] Network resources

• No issues found!

Version: 3.3.1

Platform:

  • 📱 iOS
  • 🤖 Android 13 (AP I33)
Dominant language
Dart
Stars
810
Forks
510
Avg merge
2d 2h
Merged PRs (30d)
11

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

More from Baseflow/flutter_cache_manager

All issues in Baseflow/flutter_cache_manager

Similar issues

More Dart issues

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.