Add deprecation warnings for v7 flags in v6

.changeset/ninety-queens-thank.md

@@ -0,0 +1,9 @@
+---
+"react-router-dom": minor
+"react-router": minor
+"@remix-run/router": minor
+---
+
+- Log deprecation warnings for v7 flags
+- Add deprecation warnings to `json`/`defer` in favor of returning raw objects
+  - These methods will be removed in React Router v7

package.json

@@ -108,16 +108,16 @@
       "none": "58.1 kB"
     },
     "packages/react-router/dist/react-router.production.min.js": {
-      "none": "15.0 kB"
+      "none": "16.5 kB"
     },
     "packages/react-router/dist/umd/react-router.production.min.js": {
-      "none": "17.5 kB"
+      "none": "19.0 kB"
     },
     "packages/react-router-dom/dist/react-router-dom.production.min.js": {
-      "none": "17.3 kB"
+      "none": "17.5 kB"
     },
     "packages/react-router-dom/dist/umd/react-router-dom.production.min.js": {
-      "none": "23.8 kB"
+      "none": "24.0 kB"
     }
   },
   "pnpm": {

packages/react-router-dom/__tests__/exports-test.tsx

@@ -2,6 +2,7 @@ import * as ReactRouter from "react-router";
 import * as ReactRouterDOM from "react-router-dom";
 
 let nonReExportedKeys = new Set([
+  "UNSAFE_logV6DeprecationWarnings",
   "UNSAFE_mapRouteProperties",
   "UNSAFE_useRoutesImpl",
 ]);

packages/react-router-dom/__tests__/scroll-restoration-test.tsx

@@ -39,9 +39,21 @@ describe(`ScrollRestoration`, () => {
           children: testPages,
         },
       ],
-      { basename: "/base", window: testWindow }
+      {
+        basename: "/base",
+        window: testWindow,
+        future: {
+          v7_fetcherPersist: true,
+          v7_normalizeFormMethod: true,
+          v7_partialHydration: true,
+          v7_skipActionErrorRevalidation: true,
+          v7_relativeSplatPath: true,
+        },
+      }
+    );
+    let { container } = render(
+      <RouterProvider router={router} future={{ v7_startTransition: true }} />
     );
-    let { container } = render(<RouterProvider router={router} />);
 
     expect(getHtml(container)).toMatch("On page 1");
 

packages/react-router-dom/index.tsx

@@ -33,6 +33,7 @@ import {
   UNSAFE_DataRouterStateContext as DataRouterStateContext,
   UNSAFE_NavigationContext as NavigationContext,
   UNSAFE_RouteContext as RouteContext,
+  UNSAFE_logV6DeprecationWarnings as logV6DeprecationWarnings,
   UNSAFE_mapRouteProperties as mapRouteProperties,
   UNSAFE_useRouteId as useRouteId,
   UNSAFE_useRoutesImpl as useRoutesImpl,
@@ -716,6 +717,11 @@ export function RouterProvider({
     [router.future.v7_relativeSplatPath]
   );
 
+  React.useEffect(
+    () => logV6DeprecationWarnings(future, router.future),
+    [future, router.future]
+  );
+
   // The fragment and {null} here are important!  We need them to keep React 18's
   // useId happy when we are server-rendering since we may have a <script> here
   // containing the hydrated server-side staticContext (from StaticRouterProvider).
@@ -807,6 +813,8 @@ export function BrowserRouter({
 
   React.useLayoutEffect(() => history.listen(setState), [history, setState]);
 
+  React.useEffect(() => logV6DeprecationWarnings(future), [future]);
+
   return (
     <Router
       basename={basename}
@@ -858,6 +866,8 @@ export function HashRouter({
 
   React.useLayoutEffect(() => history.listen(setState), [history, setState]);
 
+  React.useEffect(() => logV6DeprecationWarnings(future), [future]);
+
   return (
     <Router
       basename={basename}
@@ -905,6 +915,8 @@ function HistoryRouter({
 
   React.useLayoutEffect(() => history.listen(setState), [history, setState]);
 
+  React.useEffect(() => logV6DeprecationWarnings(future), [future]);
+
   return (
     <Router
       basename={basename}

packages/react-router-native/__tests__/exports-test.tsx

@@ -2,6 +2,7 @@ import * as ReactRouter from "react-router";
 import * as ReactRouterNative from "react-router-native";
 
 let nonReExportedKeys = new Set([
+  "UNSAFE_logV6DeprecationWarnings",
   "UNSAFE_mapRouteProperties",
   "UNSAFE_useRoutesImpl",
   "UNSAFE_ViewTransitionContext",

packages/react-router/__tests__/Router-basename-test.tsx

@@ -16,7 +16,11 @@ describe("<Router basename>", () => {
     let renderer: TestRenderer.ReactTestRenderer;
     TestRenderer.act(() => {
       renderer = TestRenderer.create(
-        <MemoryRouter basename="/app" initialEntries={["/home"]}>
+        <MemoryRouter
+          basename="/app"
+          initialEntries={["/home"]}
+          future={{ v7_startTransition: true, v7_relativeSplatPath: true }}
+        >
           <Routes>
             <Route path="/" element={<h1>App</h1>} />
           </Routes>

packages/react-router/__tests__/Routes-test.tsx

@@ -19,7 +19,9 @@ describe("<Routes>", () => {
     let renderer: TestRenderer.ReactTestRenderer;
     TestRenderer.act(() => {
       renderer = TestRenderer.create(
-        <MemoryRouter>
+        <MemoryRouter
+          future={{ v7_startTransition: true, v7_relativeSplatPath: true }}
+        >
           <Routes />
         </MemoryRouter>
       );

packages/react-router/__tests__/descendant-routes-warning-test.tsx

@@ -41,7 +41,10 @@ describe("Descendant <Routes>", () => {
 
       TestRenderer.act(() => {
         TestRenderer.create(
-          <MemoryRouter initialEntries={["/courses/react"]}>
+          <MemoryRouter
+            initialEntries={["/courses/react"]}
+            future={{ v7_startTransition: true, v7_relativeSplatPath: true }}
+          >
             <Routes>
               <Route path="courses" element={<Courses />}>
                 <Route path="react" element={<ReactCourses />} />
@@ -79,7 +82,10 @@ Please change the parent <Route path="react"> to <Route path="react/*">.`);
 
       TestRenderer.act(() => {
         TestRenderer.create(
-          <MemoryRouter initialEntries={["/"]}>
+          <MemoryRouter
+            initialEntries={["/"]}
+            future={{ v7_startTransition: true, v7_relativeSplatPath: true }}
+          >
             <Routes>
               <Route path="/" element={<ReactCourses />} />
             </Routes>
@@ -124,7 +130,10 @@ Please change the parent <Route path="/"> to <Route path="*">.`);
 
       TestRenderer.act(() => {
         TestRenderer.create(
-          <MemoryRouter initialEntries={["/courses/react"]}>
+          <MemoryRouter
+            initialEntries={["/courses/react"]}
+            future={{ v7_startTransition: true, v7_relativeSplatPath: true }}
+          >
             <Routes>
               <Route path="courses" element={<Courses />}>
                 <Route path="react/*" element={<ReactCourses />} />

packages/react-router/index.ts

@@ -124,6 +124,7 @@ import {
   useRoutes,
   useRoutesImpl,
 } from "./lib/hooks";
+import { logV6DeprecationWarnings } from "./lib/deprecations";
 
 // Exported for backwards compatibility, but not being used internally anymore
 type Hash = string;
@@ -351,4 +352,5 @@ export {
   mapRouteProperties as UNSAFE_mapRouteProperties,
   useRouteId as UNSAFE_useRouteId,
   useRoutesImpl as UNSAFE_useRoutesImpl,
+  logV6DeprecationWarnings as UNSAFE_logV6DeprecationWarnings,
 };

packages/react-router/lib/components.tsx

@@ -49,6 +49,7 @@ import {
   useRoutes,
   useRoutesImpl,
 } from "./hooks";
+import { logV6DeprecationWarnings } from "./deprecations";
 
 export interface FutureConfig {
   v7_relativeSplatPath: boolean;
@@ -154,6 +155,11 @@ export function RouterProvider({
     [router, navigator, basename]
   );
 
+  React.useEffect(
+    () => logV6DeprecationWarnings(future, router.future),
+    [router, future]
+  );
+
   // The fragment and {null} here are important!  We need them to keep React 18's
   // useId happy when we are server-rendering since we may have a <script> here
   // containing the hydrated server-side staticContext (from StaticRouterProvider).
@@ -248,6 +254,8 @@ export function MemoryRouter({
 
   React.useLayoutEffect(() => history.listen(setState), [history, setState]);
 
+  React.useEffect(() => logV6DeprecationWarnings(future), [future]);
+
   return (
     <Router
       basename={basename}

packages/react-router/lib/deprecations.ts

@@ -0,0 +1,77 @@
+import type { FutureConfig as RouterFutureConfig } from "@remix-run/router";
+import type { FutureConfig as RenderFutureConfig } from "./components";
+
+const alreadyWarned: { [key: string]: boolean } = {};
+
+export function warnOnce(key: string, message: string): void {
+  if (!alreadyWarned[message]) {
+    alreadyWarned[message] = true;
+    console.warn(message);
+  }
+}
+
+const logDeprecation = (flag: string, msg: string, link: string) =>
+  warnOnce(
+    flag,
+    `⚠️ React Router Future Flag Warning: ${msg}. ` +
+      `You can use the \`${flag}\` future flag to opt-in early. ` +
+      `For more information, see ${link}.`
+  );
+
+export function logV6DeprecationWarnings(
+  renderFuture: Partial<RenderFutureConfig> | undefined,
+  routerFuture?: Omit<RouterFutureConfig, "v7_prependBasename">
+) {
+  if (!renderFuture?.v7_startTransition) {
+    logDeprecation(
+      "v7_startTransition",
+      "React Router will begin wrapping state updates in `React.startTransition` in v7",
+      "https://reactrouter.com/v6/upgrading/future#v7_starttransition"
+    );
+  }
+
+  if (
+    !renderFuture?.v7_relativeSplatPath &&
+    (!routerFuture || !routerFuture.v7_relativeSplatPath)
+  ) {
+    logDeprecation(
+      "v7_relativeSplatPath",
+      "Relative route resolution within Splat routes is changing in v7",
+      "https://reactrouter.com/v6/upgrading/future#v7_relativesplatpath"
+    );
+  }
+
+  if (routerFuture) {
+    if (!routerFuture.v7_fetcherPersist) {
+      logDeprecation(
+        "v7_fetcherPersist",
+        "The persistence behavior of fetchers is changing in v7",
+        "https://reactrouter.com/v6/upgrading/future#v7_fetcherpersist"
+      );
+    }
+
+    if (!routerFuture.v7_normalizeFormMethod) {
+      logDeprecation(
+        "v7_normalizeFormMethod",
+        "Casing of `formMethod` fields is being normalized to uppercase in v7",
+        "https://reactrouter.com/v6/upgrading/future#v7_normalizeformmethod"
+      );
+    }
+
+    if (!routerFuture.v7_partialHydration) {
+      logDeprecation(
+        "v7_partialHydration",
+        "`RouterProvider` hydration behavior is changing in v7",
+        "https://reactrouter.com/v6/upgrading/future#v7_partialhydration"
+      );
+    }
+
+    if (!routerFuture.v7_skipActionErrorRevalidation) {
+      logDeprecation(
+        "v7_skipActionErrorRevalidation",
+        "The revalidation behavior after 4xx/5xx `action` responses is changing in v7",
+        "https://reactrouter.com/v6/upgrading/future#v7_skipactionerrorrevalidation"
+      );
+    }
+  }
+}

packages/router/utils.ts

@@ -1366,6 +1366,9 @@ export type JsonFunction = <Data>(
 /**
  * This is a shortcut for creating `application/json` responses. Converts `data`
  * to JSON and sets the `Content-Type` header.
+ *
+ * @deprecated The `json` method is deprecated in favor of returning raw objects.
+ * This method will be removed in v7.
  */
 export const json: JsonFunction = (data, init = {}) => {
   let responseInit = typeof init === "number" ? { status: init } : init;
@@ -1604,6 +1607,10 @@ export type DeferFunction = (
   init?: number | ResponseInit
 ) => DeferredData;
 
+/**
+ * @deprecated The `defer` method is deprecated in favor of returning raw
+ * objects. This method will be removed in v7.
+ */
 export const defer: DeferFunction = (data, init = {}) => {
   let responseInit = typeof init === "number" ? { status: init } : init;