fix: populate value for Netlify React Router context in dev

packages/vite-plugin-react-router/README.md

@@ -3,27 +3,37 @@
 The React Router Adapter for Netlify allows you to deploy your [React Router](https://reactrouter.com) app to
 [Netlify Functions](https://docs.netlify.com/functions/overview/).
 
-To deploy a React Router 7+ site to Netlify, install this package:
-
 ## How to use
 
+To deploy a React Router 7+ site to Netlify, install this package:
+
 ```sh
 npm install --save-dev @netlify/vite-plugin-react-router
 ```
 
+It's also recommended (but not required) to use the
+[Netlify Vite plugin](https://www.npmjs.com/package/@netlify/vite-plugin), which provides full Netlify platform
+emulation directly in your local dev server:
+
+```sh
+npm install --save-dev @netlify/vite-plugin
+```
+
 and include the Netlify plugin in your `vite.config.ts`:
 
 ```typescript
 import { reactRouter } from '@react-router/dev/vite'
 import { defineConfig } from 'vite'
 import tsconfigPaths from 'vite-tsconfig-paths'
-import netlifyPlugin from '@netlify/vite-plugin-react-router' // <- add this
+import netlifyReactRouter from '@netlify/vite-plugin-react-router' // <- add this
+import netlify from '@netlify/vite-plugin' // <- add this (optional)
 
 export default defineConfig({
   plugins: [
     reactRouter(),
     tsconfigPaths(),
-    netlifyPlugin(), // <- add this
+    netlifyReactRouter(), // <- add this
+    netlify(), // <- add this (optional)
   ],
 })
 ```
@@ -76,6 +86,12 @@ export default function Example() {
 }
 ```
 
+> [!IMPORTANT]
+>
+> Note that in local development, `netlifyRouterContext` requires Netlify platform emulation, which is provided
+> seamlessly by [`@netlify/vite-plugin`](https://www.npmjs.com/package/@netlify/vite-plugin) (or Netlify CLI - up to
+> you).
+
 ### Middleware context
 
 React Router introduced a stable middleware feature in 7.9.0.
@@ -103,3 +119,9 @@ export default function Home() {
   return <h1>Hello world</h1>
 }
 ```
+
+> [!IMPORTANT]
+>
+> Note that in local development, `netlifyRouterContext` requires Netlify platform emulation, which is provided
+> seamlessly by [`@netlify/vite-plugin`](https://www.npmjs.com/package/@netlify/vite-plugin) (or Netlify CLI - up to
+> you).

packages/vite-plugin-react-router/src/server.ts

@@ -41,7 +41,36 @@ export type RequestHandler = (request: Request, context: NetlifyContext) => Prom
  *
  * @example context.get(netlifyRouterContext).geo?.country?.name
  */
-export const netlifyRouterContext = createContext<NetlifyContext>()
+export const netlifyRouterContext =
+  // We must use a singleton because Remix contexts rely on referential equality.
+  // We can't hook into the request lifecycle in dev mode, so we use a Proxy to always read from the
+  // current `Netlify.context` value, which is always contextual to the in-flight request.
+  createContext<Partial<NetlifyContext>>(
+    new Proxy(
+      // Can't reference `Netlify.context` here because it isn't set outside of a request lifecycle
+      {},
+      {
+        get(_target, prop, receiver) {
+          return Reflect.get(Netlify.context ?? {}, prop, receiver)
+        },
+        set(_target, prop, value, receiver) {
+          return Reflect.set(Netlify.context ?? {}, prop, value, receiver)
+        },
+        has(_target, prop) {
+          return Reflect.has(Netlify.context ?? {}, prop)
+        },
+        deleteProperty(_target, prop) {
+          return Reflect.deleteProperty(Netlify.context ?? {}, prop)
+        },
+        ownKeys(_target) {
+          return Reflect.ownKeys(Netlify.context ?? {})
+        },
+        getOwnPropertyDescriptor(_target, prop) {
+          return Reflect.getOwnPropertyDescriptor(Netlify.context ?? {}, prop)
+        },
+      },
+    ),
+  )
 
 /**
  * Given a build and a callback to get the base loader context, this returns