React 18

README.md

API

Q: Why do we need a new API? instead of render/hydrate+unmountComponentAtNode A: reactwg/react-18#5 (comment)

testing

• Existing act() issues
  1. Bug: act warning misleading if an effect wasn't run
  2. Should act() warnings be deduplicated by component stack?
  3. Bug: error in effect cleanup function no longer catchable
  4. Flush discrete updates immediately in a batched context
  5. testing build (facebook/react#19745, facebook/react#18196)
  6. setup mock scheduler in a fresh cra throws "messageParent" can only be used inside a worker scheduler/unstable_mock will be obsolete
• await act() required for discrete events (reactwg/react-18#23)
• Mocking scheduler requires setup and only a solution in jest exists (reactwg/react-18#23 (reply in thread)

  -In Concurrent or Sync modes
  +In Concurrent React

• facebook/react#21765
• hydrate on the server? https://github.com/eps1lon/react/blob/2bf4805e4bd63dab45cd7f5e1ad32ef8fed3f6ab/packages/react-dom/src/__tests__/ReactDOMFizzServer-test.js#L1281-L1299

Material-UI

1. From the meeting on 2021-06-25 regarding levels: If we are level 3 compatible should we already start wrapping setState calls in startTransition (e.g. TextField onChange)?

   Ideally almost every update should be wrapped in a transition somehow.

   -- reactwg/react-18#63 (comment)