provide access to request context via event.platform (#9280)

* provide access to request context via `event.platform` - closes #8706

* cheat

Author: Rich-Harris

.changeset/polite-files-relate.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/adapter-vercel': minor
+---
+
+feat: provide access to request context via `event.platform`

packages/adapter-vercel/ambient.d.ts

@@ -1,8 +1,12 @@
-declare module 'SERVER' {
-	export { Server } from '@sveltejs/kit';
-}
+import { RequestContext } from './index.js';
 
-declare module 'MANIFEST' {
-	import { SSRManifest } from '@sveltejs/kit';
-	export const manifest: SSRManifest;
+declare global {
+	namespace App {
+		export interface Platform {
+			/**
+			 * `context` is only available in Edge Functions
+			 */
+			context?: RequestContext;
+		}
+	}
 }

packages/adapter-vercel/files/edge.js

@@ -8,12 +8,16 @@ const initialized = server.init({
 
 /**
  * @param {Request} request
+ * @param {import('../index.js').RequestContext} context
  */
-export default async (request) => {
+export default async (request, context) => {
 	await initialized;
 	return server.respond(request, {
 		getClientAddress() {
 			return /** @type {string} */ (request.headers.get('x-forwarded-for'));
+		},
+		platform: {
+			context
 		}
 	});
 };

packages/adapter-vercel/index.d.ts

@@ -1,4 +1,5 @@
 import { Adapter } from '@sveltejs/kit';
+import './ambient.js';
 
 export default function plugin(config?: Config): Adapter;
 
@@ -77,3 +78,59 @@ export interface EdgeConfig {
 }
 
 export type Config = EdgeConfig | ServerlessConfig;
+
+// we copy the RequestContext interface from `@vercel/edge` because that package can't co-exist with `@types/node`.
+// see https://github.com/sveltejs/kit/pull/9280#issuecomment-1452110035
+
+/**
+ * An extension to the standard `Request` object that is passed to every Edge Function.
+ *
+ * @example
+ * ```ts
+ * import type { RequestContext } from '@vercel/edge';
+ *
+ * export default async function handler(request: Request, ctx: RequestContext): Promise<Response> {
+ *   // ctx is the RequestContext
+ * }
+ * ```
+ */
+export interface RequestContext {
+	/**
+	 * A method that can be used to keep the function running after a response has been sent.
+	 * This is useful when you have an async task that you want to keep running even after the
+	 * response has been sent and the request has ended.
+	 *
+	 * @example
+	 *
+	 * <caption>Sending an internal error to an error tracking service</caption>
+	 *
+	 * ```ts
+	 * import type { RequestContext } from '@vercel/edge';
+	 *
+	 * export async function handleRequest(request: Request, ctx: RequestContext): Promise<Response> {
+	 *  try {
+	 *    return await myFunctionThatReturnsResponse();
+	 *  } catch (e) {
+	 *    ctx.waitUntil((async () => {
+	 *      // report this error to your error tracking service
+	 *      await fetch('https://my-error-tracking-service.com', {
+	 *        method: 'POST',
+	 *        body: JSON.stringify({
+	 *          stack: e.stack,
+	 *          message: e.message,
+	 *          name: e.name,
+	 *          url: request.url,
+	 *        }),
+	 *      });
+	 *    })());
+	 *    return new Response('Internal Server Error', { status: 500 });
+	 *  }
+	 * }
+	 * ```
+	 */
+	waitUntil(
+		/**
+		 * A promise that will be kept alive until it resolves or rejects.
+		 */ promise: Promise<unknown>
+	): void;
+}

packages/adapter-vercel/internal.d.ts

@@ -0,0 +1,8 @@
+declare module 'SERVER' {
+	export { Server } from '@sveltejs/kit';
+}
+
+declare module 'MANIFEST' {
+	import { SSRManifest } from '@sveltejs/kit';
+	export const manifest: SSRManifest;
+}

packages/adapter-vercel/tsconfig.json

@@ -14,5 +14,5 @@
 			"@sveltejs/kit": ["../kit/types/index"]
 		}
 	},
-	"include": ["**/*.js", "ambient.d.ts"]
+	"include": ["**/*.js", "index.d.ts", "internal.d.ts"]
 }