Bug: Dropped update when render phase update happens before suspending

[gaearon]

Sandbox: https://codesandbox.io/s/cranky-kapitsa-op3jh

Repro: type "a" and then after a second "b"

Expected: Eventually you'll see "ab" in all fields. Pending "..." indicator goes away.

Actual: You'll keep seeing "a" in low pri field. Pending "..." indicator is stuck.

[VakoNonikashvili]

Sandbox: https://codesandbox.io/s/nostalgic-gauss-xrn4o (If I understand problem correctly)

Why didn't you update mirror text with useEffect?

[gaearon]

Generally saying, render phase updates are better for derived state because you don’t need an extra rendering pass for the whole subtree.

In either case, it doesn’t matter how else I could write it. The problem is that this uncovers a bug in React, and bugs need to be fixed.