Erich Graham
fa4045e4dd
Summary: Pull Request resolved: https://github.com/facebook/react-native/pull/31543 Changelog: [iOS][Added] - Description When compiling iOS apps with flag `-Wnullability-completeness` (like Lightspeed app and soon Instagram), Objective-C headers are required to either have full *explicit* nullability annotations on all members of its public API, or none at all; partially annotated headers will fail to build that module. RN native modules are currently generated with *partial* annotations. This works today because most apps are not compiled with `-Wnullability-completeness` turned on. But when we flip the switch for Instagram, the app doesn't build due to importing these RN partially annotated modules. JavsScript Flow types are implied nonnull, and the current RN codegen translates Flow's [maybe/optional](https://flow.org/en/docs/types/maybe/) type to Obj-C `_Nullable` annotation, and everything else without an explicit Obj-C annotation. However this creates a mismatch with the Obj-C type system, where the implied default is *unannotated*, which is handled differently from nonnull when built with the nullability compiler flags. There is a simple Obj-C macro that automatically adds *explicit nonnull* annotations to all members in a header: `NS_ASSUME_NONNULL_BEGIN` / `NS_ASSUME_NONNULL_END`. If we add this to *all* RN-generated headers, however, we run into issues: 1) We may erroneously assume any previously-unannotated header was meant to be nonnull and cause future bugs 2) Another compiler flag (`-Wnullable-to-nonnull-conversion`) statically analyzes Obj-C implementation code to prevent us from ever passing null to one of these headers. Much existing Obj-C code will break here, and it's ambiguous if these are true or false positives because of the first point. Instead, in this diff we add a new BUCK flag `ios_assume_nonnull` to let module authors opt into automatic nonnull for unannotated members so that Obj-C headers are generated correctly in alignment with Flow's type system. We can migrate all libraries individually as needed and eventually make this the RN native codegen default. Reviewed By: RSNara Differential Revision: D28396446 fbshipit-source-id: ad3a3a97ab19183df4ef504b1c3140596c8f69ca
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 11.0 and Android 5.0 (API 21) 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 repo, @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 the React Native Community, @react-native-community/react-native-releases.
👏 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.