Use Select: Fix render queue.

packages/data/package.json

@@ -34,7 +34,8 @@
 		"lodash": "^4.17.15",
 		"memize": "^1.0.5",
 		"redux": "^4.0.0",
-		"turbo-combine-reducers": "^1.0.2"
+		"turbo-combine-reducers": "^1.0.2",
+		"use-memo-one": "^1.1.1"
 	},
 	"publishConfig": {
 		"access": "public"

packages/data/src/components/use-select/index.js

@@ -1,11 +1,15 @@
+/**
+ * External dependencies
+ */
+import { useMemoOne } from 'use-memo-one';
+
 /**
  * WordPress dependencies
  */
 import { createQueue } from '@wordpress/priority-queue';
 import {
 	useLayoutEffect,
 	useRef,
-	useMemo,
 	useCallback,
 	useEffect,
 	useReducer,
@@ -78,14 +82,17 @@ export default function useSelect( _mapSelect, deps ) {
 	const mapSelect = useCallback( _mapSelect, deps );
 	const registry = useRegistry();
 	const isAsync = useAsyncMode();
-	const queueContext = useMemo( () => ( { queue: true } ), [ registry ] );
+	// React can sometimes clear the `useMemo` cache.
+	// We use the cache-stable `useMemoOne` to avoid
+	// losing queues.
+	const queueContext = useMemoOne( () => ( { queue: true } ), [ registry ] );
 	const [ , forceRender ] = useReducer( ( s ) => s + 1, 0 );
 
 	const latestMapSelect = useRef();
 	const latestIsAsync = useRef( isAsync );
 	const latestMapOutput = useRef();
 	const latestMapOutputError = useRef();
-	const isMounted = useRef();
+	const isMountedAndNotUnsubscribing = useRef();
 
 	let mapOutput;
 
@@ -96,9 +103,7 @@ export default function useSelect( _mapSelect, deps ) {
 			mapOutput = latestMapOutput.current;
 		}
 	} catch ( error ) {
-		let errorMessage = `An error occurred while running 'mapSelect': ${
-			error.message
-		}`;
+		let errorMessage = `An error occurred while running 'mapSelect': ${ error.message }`;
 
 		if ( latestMapOutputError.current ) {
 			errorMessage += `\nThe error may be correlated with this previous error:\n`;
@@ -111,18 +116,23 @@ export default function useSelect( _mapSelect, deps ) {
 
 	useIsomorphicLayoutEffect( () => {
 		latestMapSelect.current = mapSelect;
+		latestMapOutput.current = mapOutput;
+		latestMapOutputError.current = undefined;
+		isMountedAndNotUnsubscribing.current = true;
+
+		// This has to run after the other ref updates
+		// to avoid using stale values in the flushed
+		// callbacks or potentially overwriting a
+		// changed `latestMapOutput.current`.
 		if ( latestIsAsync.current !== isAsync ) {
 			latestIsAsync.current = isAsync;
 			renderQueue.flush( queueContext );
 		}
-		latestMapOutput.current = mapOutput;
-		latestMapOutputError.current = undefined;
-		isMounted.current = true;
 	} );
 
 	useIsomorphicLayoutEffect( () => {
 		const onStoreChange = () => {
-			if ( isMounted.current ) {
+			if ( isMountedAndNotUnsubscribing.current ) {
 				try {
 					const newMapOutput = latestMapSelect.current(
 						registry.select,
@@ -156,7 +166,7 @@ export default function useSelect( _mapSelect, deps ) {
 		} );
 
 		return () => {
-			isMounted.current = false;
+			isMountedAndNotUnsubscribing.current = false;
 			unsubscribe();
 			renderQueue.flush( queueContext );
 		};