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Andrew Clark
94518b068b
* Add stack unwinding phase for handling errors A rewrite of error handling, with semantics that more closely match stack unwinding. Errors that are thrown during the render phase unwind to the nearest error boundary, like before. But rather than synchronously unmount the children before retrying, we restart the failed subtree within the same render phase. The failed children are still unmounted (as if all their keys changed) but without an extra commit. Commit phase errors are different. They work by scheduling an error on the update queue of the error boundary. When we enter the render phase, the error is popped off the queue. The rest of the algorithm is the same. This approach is designed to work for throwing non-errors, too, though that feature is not implemented yet. * Add experimental getDerivedStateFromCatch lifecycle Fires during the render phase, so you can recover from an error within the same pass. This aligns error boundaries more closely with try-catch semantics. Let's keep this behind a feature flag until a future release. For now, the recommendation is to keep using componentDidCatch. Eventually, the advice will be to use getDerivedStateFromCatch for handling errors and componentDidCatch only for logging. * Reconcile twice to remount failed children, instead of using a boolean * Handle effect immediately after its thrown This way we don't have to store the thrown values on the effect list. * ReactFiberIncompleteWork -> ReactFiberUnwindWork * Remove startTime * Remove TypeOfException We don't need it yet. We'll reconsider once we add another exception type. * Move replay to outer catch block This moves it out of the hot path.
react-test-renderer
This package provides an experimental React renderer that can be used to render React components to pure JavaScript objects, without depending on the DOM or a native mobile environment.
Essentially, this package makes it easy to grab a snapshot of the "DOM tree" rendered by a React DOM or React Native component without using a browser or jsdom.
Usage:
const ReactTestRenderer = require('react-test-renderer');
const renderer = ReactTestRenderer.create(
<Link page="https://www.facebook.com/">Facebook</Link>
);
console.log(renderer.toJSON());
// { type: 'a',
// props: { href: 'https://www.facebook.com/' },
// children: [ 'Facebook' ] }
You can also use Jest's snapshot testing feature to automatically save a copy of the JSON tree to a file and check in your tests that it hasn't changed: https://facebook.github.io/jest/blog/2016/07/27/jest-14.html.