🏠 Compile Invariant Directly to Throw Expressions

React uses invariant() to assert correct behavior. In production, the error message is stripped out to keep the bundle size down. This PR reworks how this is handled.
https://github.com/facebook/react/pull/15071

🌅 Shallow Renderer: Implement setState for Hooks

The shallow renderer now supports calling the setState updater of useState() hooks outside of the render function.
https://github.com/facebook/react/pull/15120

📖 Docs: How Can I Measure a DOM Node?

The React Hooks FAQs now contain a new entry with information on how to best measure DOM nodes.
https://reactjs.org/docs/hooks-faq.html#how-can-i-measure-a-dom-node

🖱 Internal Event API Experiments Updates

While working on internal experiments for a new event API, the Core team added more scaffolding, a new react-events package, and logic for listening to event responders.
https://github.com/facebook/react/pull/15168

⛑ Add Feature Flag to Disable Yielding

A new feature flag was added that allows debug builds to disable yielding in Concurrent Mode.
https://github.com/facebook/react/pull/15119

📌 React v16.8.5 Patch Release

This release includes a improved warnings and support for newer features in the shallow renderer.
https://github.com/facebook/react/releases/tag/v16.8.5

🕹 Internal Event API Experiments Updates

This week added more parts to the internal event API experiments including event component responder surfaces and SSR support.

https://github.com/facebook/react/pull/15179

💃 Dancing Between State and Effects

James Long (jlongster) started a discussion about ways to combine effects and state changes. Feedback welcome!

https://github.com/facebook/react/issues/15240

🎚 Enabled warnAboutDeprecatedLifecycles

React will, starting with the next minor version, warn when deprecated lifecycle methods are used. You can learn more about this deprecation in this blog post.

https://reactjs.org/blog/2018/03/27/update-on-async-rendering.html

https://github.com/facebook/react/pull/15186

🌍 Turkish Localization Completed

The Turkish localization is now complete, making it the eight complete localization.

https://tr.reactjs.org/

⚠️ Warn About Async Infinite useEffect loop

This PR adds a warning for an infinite useEffect loop caused by calling setState without defining a dependency array or one of the dependencies changes on every render.

https://github.com/facebook/react/pull/15180

📌 React v16.8.6 Patch Release

This release includes a fix for useReducer() bailout and a fix for cross-origin iframes in Safari as well as two new warnings related to contextType.

https://github.com/facebook/react/releases/tag/v16.8.6

💙 Rachel Nabors Joining the React Core Team

Rachel Nabors (rachelnabors) will join the React Core team in May and will be writing docs, building demos, and tending the community. I can’t be more excited!

https://twitter.com/rachelnabors/status/1112699525528018945

🎉 await act(async () => ...)

The recently added act test helper now has support for async functions allowing you await within its callback.

https://github.com/facebook/react/pull/14853

🔥 Experimental React Flare Updates

React Flare (the current name for the internal event API experiments) got a lot more updates this week. Check out this umbrella ticket for an overview of the current status.
Note: This idea is currently in early experimentation phase and might be discarded altogether.

https://github.com/facebook/react/issues/15257

⏱ Rewrite ReactFiberScheduler for Better Integration With Scheduler Package

This PR adds a new ReactFiberScheduler implementation (currently behind a feature flag) that better integrations with the Scheduler package.

https://github.com/facebook/react/pull/15151

🕰 Remove maxDuration

The maxDuration property of React.Suspense, used in Concurrent Mode, was removed. A heuristics with a different mechanism will be used in the future.

https://github.com/facebook/react/pull/15272

🌏 React Docs Localizations Updates

Italian is now complete:
- it.reactjs.org
And the Traditional Chinese documentation website is now online:

https://zh-hant.reactjs.org/

🔧 Fix a Crash in Suspense With findDOMNode

The Core team worked on a fix for a crash when using findDOMNode in a suspended component.

https://github.com/facebook/react/pull/15312

✨ Provide New JSX Transform Target

This PR exposes two new top-level exports: jsx and jsxs. It’s a first step toward the changes described in RFC #107 and is backward compatible to createElement.

https://github.com/facebook/react/pull/15141

🐌 Apply the Just Noticeable Difference to Suspense Timeouts

With this change, the suspended time is increased, based on how long a user has already waiting. Check out the underlying theory on Wikipedia.

https://github.com/facebook/react/pull/15367