Fix up memoization of useTransition

brophdawg11 · brophdawg11 · commit aa774f400c7d · 2022-12-14T10:27:49.000-05:00
diff --git a/integration/rendering-test.ts b/integration/rendering-test.ts
@@ -9,7 +9,6 @@ test.describe("rendering", () => {
   let appFixture: AppFixture;
 
   test.beforeAll(async () => {
-    process.env.NODE_ENV = "development";
     fixture = await createFixture({
       files: {
         "app/root.jsx": js`
diff --git a/integration/transition-state-test.ts b/integration/transition-state-test.ts
@@ -32,11 +32,6 @@ test.describe("rendering", () => {
           export default function() {
             const transition = useTransition();
 
-            // TODO: This seems to have some issues with StrictMode?
-            //  - Passes running only transition tests w/StrictMode
-            //  - Passes on full suite with fullyParallel:false w/StrictMode
-            //  - Fails on full suite with fullyParallel:true w/StrictMode
-            //  - Passes on full suite with fullyParallel:true w/o StrictMode
             const transitionsRef = useRef();
             const transitions = useMemo(() => {
               const savedTransitions = transitionsRef.current || [];
@@ -47,6 +42,7 @@ test.describe("rendering", () => {
 
             return (
               <html lang="en">
+                <head><title>Test</title></head>
                 <body>
                   <Outlet />
                     {transition.state != "idle" && (
diff --git a/packages/remix-react/components.tsx b/packages/remix-react/components.tsx
@@ -796,6 +796,7 @@ import(${JSON.stringify(manifest.entry.module)});`;
         />
         <script
           {...props}
+          suppressHydrationWarning
           dangerouslySetInnerHTML={createHtml(routeModulesScript)}
           type="module"
           async
@@ -957,10 +958,22 @@ export function useActionData<T = AppData>(): SerializeFrom<T> | undefined {
  */
 export function useTransition(): Transition {
   let navigation = useNavigation();
-  return React.useMemo(
-    () => convertNavigationToTransition(navigation),
-    [navigation]
-  );
+
+  // Have to avoid useMemo here to avoid introducing unstable transition object
+  // identities in StrictMode, since navigation will be stable but using
+  // [navigation] as the dependency array will _still_ re-run on concurrent
+  // renders, and that will create a new object identify for transition
+  let lastNavigationRef = React.useRef<Navigation>();
+  let lastTransitionRef = React.useRef<Transition>();
+
+  if (lastTransitionRef.current && lastNavigationRef.current === navigation) {
+    return lastTransitionRef.current;
+  }
+
+  lastNavigationRef.current = navigation;
+  lastTransitionRef.current = convertNavigationToTransition(navigation);
+
+  return lastTransitionRef.current;
 }
 
 function convertNavigationToTransition(navigation: Navigation): Transition {
