* Replace react-redux with a preact context binding
One of the two packages holding the @preact/compat alias in place, and
the contained one: the store is plain redux, and the only react-redux
import inside it was a single line re-exporting typed hooks.
* Drop the now-unused react-redux types
* Subscribe before paint and check once on subscribe
Previously, useSelector subscribed to the store inside useEffect, which
runs after paint. A dispatch landing between render and that effect was
never delivered, since the listener did not exist yet, so the component
kept rendering a stale value until some later unrelated dispatch happened
to differ from the stale ref.
Subscribing in useLayoutEffect narrows the window to before paint, and
running the check once immediately on subscribe closes it, which is what
react-redux does for the same reason.
Adds the first tests for the binding, one of which fails without this
change: the store holds 1 while the DOM still shows 0.
* Only re-check on subscribe when the state actually moved
The subscribe-time check ran unconditionally, so it re-ran the selector
at mount. A selector building a fresh object fails Object.is against the
value the render already computed, which forced a second render of every
connected component: ConnectedRoot and every ConnectedComment, so around
201 extra renders for a 200-comment thread.
Reducers return a new root object on every change, so an unchanged state
reference means no dispatch was missed and the check has nothing to find.
Comparing against the state the render used keeps the property the check
exists for while dropping the extra render.
The race test still exercises the guarded path, since its dispatch
produces a new state object, and a new test pins the mount case: it fails
without the guard.
Raised by umputun in review.
Dmitry VerkhoturovandGitHub
a91e322d5c