Rubén Norte
0f2a53d04b
Summary: Pull Request resolved: https://github.com/facebook/react-native/pull/49981 Changelog: [internal] (because MutationObserver isn't a public API yet) ## Context `MutationObserver` is a [JavaScript API](https://developer.mozilla.org/en-US/docs/Web/API/MutationObserver) used to report mutations in the DOM tree. The mutations available on Web are: changing children, changing attributes and changing text. In React Native, only changing children is supported. Mutation detection needs to happen synchronously when mutations happen (in ShadowTree commits) and the notification is dispatched as a microtask in JS, which means we can only report mutations happening in JavaScript. There's an assumption that only React (in JS) can change the structure of the tree in Fabric, so we implemented `MutationObserver` considering this assummption. Unfortunately, while the assumption is correct (we can only mutate children from React) the implementation didn't take into account that commit hooks were triggered from multiple threads, even if the structure doesn't change (e.g.: with Fabric state updates). In this case, we do the checks but we never dispatch the notifications. This can cause crashes (see T217617393) if we try to check for mutations from the main thread while we add new observers in the JS thread (because that logic wasn't thread safe). This fixes that crash by, in MutationObserver, not only preventing notifications from commits not coming from React, but also preventing the determination altogether. In order to do this, this modifies the signature of the commit hooks to also pass the commit options, and adds a new field in the commit options with the source of the commit (for now, just "React" or "Unknown"). In `MutationObserver`, before accessing the data structures of the observer, we check if the commit is coming from React, and return early otherwise. Reviewed By: javache Differential Revision: D71036705 fbshipit-source-id: 985c8f903375cbf876dce5174e04563f74d7621a
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.
Open Source Roadmap
You can learn more about our vision for React Native in the Roadmap.
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.
React Native documentation is Creative Commons licensed, as found in the LICENSE-docs file.