emulate context in dev mode

packages/netlify/src/integration-base.ts

@@ -5,6 +5,7 @@ import fs from 'node:fs';
 import { fileURLToPath } from 'node:url';
 import { generateEdgeMiddleware } from './middleware.ts';
 import { createRedirects, type Options } from './shared.ts';
+import type { Connect } from 'vite';
 
 export const NETLIFY_EDGE_MIDDLEWARE_FILE = 'netlify-edge-middleware';
 
@@ -34,6 +35,7 @@ export function getAdapter(options: Required<Options> & InternalOptions): AstroA
 interface InternalOptions {
 	adapterName: string;
 	functionType: 'lambda-compatible' | 'builders' | 'v2';
+	devMiddleware?: Connect.HandleFunction
 	dist?: URL
 }
 
@@ -42,11 +44,12 @@ class StacklessError extends Error { trace = undefined }
 export function getIntegration({
 	dist,
 	adapterName,
-	binaryMediaTypes = [],
+	functionType,
+	devMiddleware,
 	builders = false,
+	binaryMediaTypes = [],
 	functionPerRoute = false,
 	edgeMiddleware = false,
-	functionType
 }: Options & InternalOptions): AstroIntegration {
 
 	if (functionType === 'v2' && builders) {
@@ -96,6 +99,9 @@ export function getIntegration({
 					logger.warn('Otherwise, this adapter is not required to deploy a static site to Netlify.');
 				}
 			},
+			'astro:server:setup' ({ server }) {
+				if (devMiddleware) server.middlewares.use(devMiddleware)
+			},
 			async 'astro:build:done' ({ routes, dir }) {
 				const functionsConfig = {
 					version: 1,

packages/netlify/src/integration-v2.ts

@@ -1,10 +1,61 @@
 import { getIntegration } from "./integration-base.ts";
 import type { Options } from "./shared.ts";
+import type { Connect } from "vite";
 
 export default function (options: Omit<Options, "builders">) {
     return getIntegration({
         ...options,
         adapterName: "@astrojs/netlify/v2",
-        functionType: "v2"
+        functionType: "v2",
+        devMiddleware
     });
 }
+
+function devMiddleware([ request ]: Parameters<Connect.SimpleHandleFunction>) {
+    const context = Object.assign(Object.create(duplicatedContext), demoContext, { rewrite })
+    Reflect.set(
+        request,
+        Symbol.for("astro.locals"),
+        { context }
+    );
+}
+
+// these properties of netlify context have equivalents in Astro
+// we want to avoid providing multiple ways of doing the same thing
+const duplicatedContext = {
+    get cookies() { throw new Error("Please use Astro.cookies or context.cookies instead.") },
+    get ip () { throw new Error("Please use Astro.clientAddress or context.clientAddress instead.") },
+    get json() { throw new Error("Please use Response.json instead.") },
+    get params() { throw new Error("Please use Astro.params or context.params instead.") },
+}
+
+const demoContext = {
+    account: { id: '66825ac773b8b53ec7a92755' },
+    deploy: { id: '67a781b80398785b0bb556f2' },
+    geo: {
+        city: 'Zurich',
+        country: { code: 'CH', name: 'Switzerland' },
+        subdivision: { code: 'ZH', name: 'Zurich' },
+        timezone: 'Europe/Zurich',
+        latitude: 47.3682,
+        longitude: 8.5671
+    },
+    log: console.log,
+    requestId: '01HFT9RZXSW1GPBE2TT7HWAJPQ',
+    server: { region: 'us-east-1' },
+    site: {
+        id: '345f2a26-befd-45f1-ada1-655d33d6e3d8',
+        name: 'your-site-name',
+        url: 'https://your-site-name.netlify.app'
+    }
+}
+
+function rewrite(input: string | URL, orginalUrl: string) {
+
+    const destinationUrl =
+        input instanceof URL ? input :
+        input.startsWith("/") ? new URL(input, orginalUrl) :
+        new URL(input);
+
+    return fetch(destinationUrl);
+}