fix(react-router/router): remove unused client side middleware future flag (#14213)

Author: brophdawg11

.changeset/brown-ladybugs-yawn.md

@@ -0,0 +1,8 @@
+---
+"react-router": patch
+---
+
+[UNSTABLE] Remove Data Mode `future.unstable_middleware` flag from `createBrowserRouter`
+
+- This is only needed as a Framework Mode flag because of the route modules and the `getLoadContext` type behavior change
+- In Data Mode, it's an opt-in feature because it's just a new property on a route object, so there's no behavior changes that necessitate a flag

docs/how-to/middleware.md

@@ -133,17 +133,9 @@ function getLoadContext(req, res) {
 
 ## Quick Start (Data Mode)
 
-### 1. Enable the middleware flag
+<docs-info>Note there is no future flag in Data Mode because you can opt-into middleware by adding it to your routes, no breaking changes exist that require a future flag.</docs-info>
 
-```tsx
-const router = createBrowserRouter(routes, {
-  future: {
-    unstable_middleware: true,
-  },
-});
-```
-
-### 2. Create a context
+### 1. Create a context
 
 Middleware uses a `context` provider instance to provide data down the middleware chain.
 You can create type-safe context objects using [`unstable_createContext`][createContext]:
@@ -156,7 +148,7 @@ export const userContext =
   unstable_createContext<User | null>(null);
 ```
 
-### 3. Add middleware to your routes
+### 2. Add middleware to your routes
 
 ```tsx
 import { redirect } from "react-router";
@@ -216,17 +208,14 @@ export default function Profile() {
 }
 ```
 
-### 4. Add an `unstable_getContext` function (optional)
+### 3. Add an `unstable_getContext` function (optional)
 
 If you wish to include a base context on all navigations/fetches, you can add an [`unstable_getContext`][getContext] function to your router. This will be called to populate a fresh context on every navigation/fetch.
 
 ```tsx
 let sessionContext = unstable_createContext();
 
 const router = createBrowserRouter(routes, {
-  future: {
-    unstable_middleware: true,
-  },
   unstable_getContext() {
     let context = new unstable_RouterContextProvider();
     context.set(sessionContext, getSession());

packages/react-router/lib/router/router.ts

@@ -384,9 +384,7 @@ export type HydrationState = Partial<
 /**
  * Future flags to toggle new feature behavior
  */
-export interface FutureConfig {
-  unstable_middleware: boolean;
-}
+export interface FutureConfig {}
 
 /**
  * Initialization options for createRouter
@@ -879,7 +877,6 @@ export function createRouter(init: RouterInit): Router {
 
   // Config driven behavior flags
   let future: FutureConfig = {
-    unstable_middleware: false,
     ...init.future,
   };
   // Cleanup function for history