629708beda
Summary: <!-- Explain the **motivation** for making this change. What existing problem does the pull request solve? --> I have used RN for a long time, and for all this time, crash reporting has been less great than native development crash reporting. At some point, companies like sentry, bugsnag and a bunch of others started supporting sourcemaps for js crashes in RN, which helped a lot. But native crashes were (and still are) much harder to diagnose. ..Until now :D I have make a repo of a sample RN app, included this PR in it, and some code and screenshots to help. The repo is [here](https://github.com/pvinis/react-native-project-with-crash-heaven-pr). I was trying to get good crash reports from native crashes in iOS for a looong time. I spoke with people in sentry, in bugsnag and more, and I could not get this solved. There was no clear way to get the **native** crashed to display correctly. I made two repos here, one for [sentry](https://github.com/pvinis/SentryBadStack) and one for [bugsnag](https://github.com/pvinis/BugsnagBadStack), demonstrating the correct js handling and the bad native handling. After all this, and talks with their support, twitter etc, I investigated further, on **why** this was happening. I thought there must be some reason that native crashes look bad in all the tools, and in the same way. Maybe it's not their fault, or up to them to fix it, or maybe they didn't have the experience to fix it. In a test project I created, I checked what's up with the `RCTFatalException`, and I found out that the React Native code is catching the `NSException`s that come from any native modules of a RN app and converting it into an string and sending it to `RCTFatal` that created an `NSError` out of that string. Then it checks if the app has set a fatal error handler and if not, goes ahead and throws that `NSError`. The problem here is that `NSException` has a bunch more info that the resulting `NSError` is missing or is altering. Turning the callstack into a string renders crash reporting tools useless as they are missing the original place the exception was thrown, symbols, return addresses etc. In both repos above it can be seen that both tools were thinking that the error happened somewhere in the `RCTFatal` function, and it did, since we create it there, losing all the previous useful info of the original exception. That leaves us with just a very long name including a callstack, but very hard to actually map this to the code and dsym. I added a fatal exception handler, that mirrors the fatal error handler, as the error handler is used around React Native internal code. Then I stopped making a string out of the original `NSException` and calling `RCTFatal`, and I simply throw the exception. This way no info is lost! Finally, I added some code examples of native and js crashes and added a part in the `RNTester` app, so people can see how a js and a native error look like while debugging, as well as try to compile the app in release mode and see how the crash report would look like if they connect it to bugsnag or sentry or their tool of choice. I have attached some images at the bottom of this PR, and you can find some in the 3 repos I linked above. [iOS] [Fixed] - Changed the way iOS native module exceptions get handled. Instead of making them into an `NSError` and lose the context and callstack, we keep them as `NSException`s and propagate them. [General] [Added] - Example code for native crashes in iOS and Android, with buttons on RNTester, so developers can see how these look when debugging, as well as the crash reports in release mode. Pull Request resolved: https://github.com/facebook/react-native/pull/23691 Reviewed By: fkgozali Differential Revision: D14276366 Pulled By: cpojer fbshipit-source-id: b308d5608e1432d7676447347ae77c0721094e62
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 own 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.
Contents
- Requirements
- Building your first React Native app
- Documentation
- Upgrading
- How to Contribute
- Code of Conduct
- License
📋 Requirements
React Native apps may target iOS 9.0 and Android 4.1 (API 16) 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 bugfixes 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.