Decide what to do with upcoming react api changes

React just published a blog post about upcoming api changes due to the planned suspense api. The current lifecycle methods will be deprecated with react v17.

We should decide if we want to follow them or leave the lifecycle methods as is. Note that our rendering process is currently not asynchronous but synchronous so we don’t have the same problems as them.

List of API changes recently introduced by react:

• getDerivedStateFromProps (#1094)
• getSnapshotBeforeUpdate (#1112)
• componentDidCatch (#819)
• Fragments (#1080)
• new Context API: currently no interest in bringing this into core (may change). preact-context is sort of a polyfill that can be used today
• UNSAFE_componentWill* won’t be added to preact, simply continue using componentWill* hooks
• ref-forwarding undecided, there hasn’t been any talk about this one yet
• createRef (#1138)
• createPortal

[marvinhagemeister]

We talked a bit on how we want to deal with the upcoming changes in yesterdays meeting. The general conclusion was to keep componentWill* hooks for now and add the new API getDerivedStateFromProps and getSnapshotBeforeUpdate. We won’t add the UNSAFE_componentWill* hooks like react did.

The reasons for changing the api are outlined in the react announcement post or in the original getDerivedStateFromProps and getSnapshotBeforeUpdate rfcs. Note that some arguments made there don’t apply to preact because our rendering is synchronous. To summarise:

getDerivedStateFromProps:

• called when a component is created and when it receives new props.
• static, to prevent mutation of props or state

Personally, I never thought that’d be an issue until I stumbled upon a component at work that mutated both state and props in componentWillReceiveProps. Moreover the author of that code was confused why componentWillReceiveProps is not called when the component is constructed.

getSnapshotBeforeUpdate:

• called right before DOM mutations are applied
• defined as static in the initial RFC but later changed back to a normal method
• doesn’t have context argument like componentWillUpdate.

At this point I’m not sure if we need this for preact. Perhaps an alias is enough?

[andrewiggins]

Opened PR #1094 for getDerivedStateFromProps