Christoph Purrer
4bf5575490
Summary: Pull Request resolved: https://github.com/react/react-native/pull/57893 The codegen'd TurboModule `emitOn<Event>` methods invoked their `EventEmitterCallback` without checking it was set. That callback is installed by the generated `*SpecJSI` constructor, which runs when JS first looks the module up — so a native module that emits before that point invoked an empty `std::function` on iOS (`std::bad_function_call`) or a null field on Android (NPE). Native code commonly holds the module instance and pushes events well before any JS surface mounts, so call sites had to wrap every emit in a try/catch to stay crash-free. Both generators now read the callback into a local and no-op when it is absent: - ObjC++ (`serializeEventEmitter.js`): copies `_eventEmitterCallback`, calls it only if non-empty. - Java (`GenerateModuleJavaSpec.js`): copies the `Nullable CxxCallbackImpl` field and null-checks it. The local is for readability, not synchronization: the callback is installed once and never cleared, and Java reference reads are already atomic. The `setEventEmitterCallback` lambdas had a separate lifetime bug: they captured `eventEmitterMap_` by reference and looked events up with `operator[]`. The Java/ObjC module owns the callback and can outlive the C++ `*SpecJSI` that installed it, so a stale callback dereferenced a dangling map; and `operator[]` silently default-inserted a null `shared_ptr` for an unknown event name, which the next line dereferenced. They now capture a copy of the map and use a checked `find` (`serializeModule.js`, `JavaTurboModule.cpp`). Every emitter is registered before the callback is installed, so the copy is complete. Note the scope of the guarantee: it covers the ObjC++ and Java generators, which route through an `EventEmitterCallback`. A C++-only TurboModule (`<Module>CxxSpec`, from `GenerateModuleH.js`) has no callback to check — it emits through `eventEmitterMap_` entries its own constructor registers — so the "emit unconditionally" guidance is about the callback, not about emitting before construction finishes. Changelog: [General][Fixed] - TurboModule event emitters no longer throw when an event is emitted before the emitter callback is installed Reviewed By: javache Differential Revision: D115130767 fbshipit-source-id: 7d7b9a706b8983968e3e1207b22c66322f04a223
React Native
Learn once, write anywhere:
Build mobile apps with React.
Getting Started · Learn the Basics · Showcase · Contribute · Community · Support
React Native brings React's declarative UI framework to iOS and Android. With React Native, you use native UI controls and have full access to the native platform.
- Declarative. React makes it painless to create interactive UIs. Declarative views make your code more predictable and easier to debug.
- Component-Based. Build encapsulated components that manage their state, then compose them to make complex UIs.
- Developer Velocity. See local changes in seconds. Changes to JavaScript code can be live reloaded without rebuilding the native app.
- Portability. Reuse code across iOS, Android, and other platforms.
React Native is developed and supported by many companies and individual core contributors. Find out more in our ecosystem overview.
Contents
- Requirements
- Building your first React Native app
- Documentation
- Upgrading
- How to Contribute
- Code of Conduct
- License
📋 Requirements
React Native apps may target iOS 15.1 and Android 7.0 (API 24) or newer. You may use Windows, macOS, or Linux as your development operating system, though building and running iOS apps is limited to macOS. Tools like Expo can be used to work around this.
🎉 Building your first React Native app
Follow the Getting Started guide. The recommended way to install React Native depends on your project. Here you can find short guides for the most common scenarios:
📖 Documentation
The full documentation for React Native can be found on our website.
The React Native documentation discusses components, APIs, and topics that are specific to React Native. For further documentation on the React API that is shared between React Native and React DOM, refer to the React documentation.
The source for the React Native documentation and website is hosted on a separate repository, @facebook/react-native-website.
🚀 Upgrading
Upgrading to new versions of React Native may give you access to more APIs, views, developer tools, and other goodies. See the Upgrading Guide for instructions.
React Native releases are discussed in this discussion repo.
👏 How to Contribute
The main purpose of this repository is to continue evolving React Native core. We want to make contributing to this project as easy and transparent as possible, and we are grateful to the community for contributing bug fixes and improvements. Read below to learn how you can take part in improving React Native.
Code of Conduct
Facebook has adopted a Code of Conduct that we expect project participants to adhere to. Please read the full text so that you can understand what actions will and will not be tolerated.
Contributing Guide
Read our Contributing Guide to learn about our development process, how to propose bugfixes and improvements, and how to build and test your changes to React Native.
Good First Issues
We have a list of good first issues that contain bugs which have a relatively limited scope. This is a great place to get started, gain experience, and get familiar with our contribution process.
Discussions
Larger discussions and proposals are discussed in @react-native-community/discussions-and-proposals.
📄 License
React Native is MIT licensed, as found in the LICENSE file.