chore: switch from hidden fields to global map

Author: ascorbic

plugin/src/middleware/request.ts

@@ -10,14 +10,6 @@ type Context = {
   next: () => Promise<Response>
 }
 
-// We sneak our own request and context into the middleware using the geo object
-type AugmentedGeo = NextRequest['geo'] & {
-  // eslint-disable-next-line camelcase
-  __nf_context: Context
-  // eslint-disable-next-line camelcase
-  __nf_request: Request
-}
-
 /**
  * Supercharge your Next middleware with Netlify Edge Functions
  */
@@ -28,14 +20,18 @@ export class MiddlewareRequest extends Request {
   constructor(private nextRequest: NextRequest) {
     super(nextRequest)
     if (!('Deno' in globalThis)) {
-      throw new Error('NetlifyMiddleware only works in a Netlify Edge Function environment')
+      throw new Error('MiddlewareRequest only works in a Netlify Edge Function environment')
+    }
+    const requestId = nextRequest.headers.get('x-nf-request-id')
+    if (!requestId) {
+      throw new Error('Missing x-nf-request-id header')
     }
-    const geo = nextRequest.geo as AugmentedGeo
-    if (!geo) {
-      throw new Error('NetlifyMiddleware must be instantiated with a NextRequest object')
+    const requestContext = globalThis.NFRequestContextMap.get(requestId)
+    if (!requestContext) {
+      throw new Error(`Could not find request context for request id ${requestId}`)
     }
-    this.context = geo.__nf_context
-    this.originalRequest = geo.__nf_request
+    this.context = requestContext.context
+    this.originalRequest = requestContext.request
   }
 
   // Add the headers to the original request, which will be passed to the origin

plugin/src/templates/edge/runtime.ts

@@ -32,6 +32,18 @@ export interface RequestData {
   body?: ReadableStream<Uint8Array>
 }
 
+export interface RequestContext {
+  request: Request
+  context: Context
+}
+
+declare global {
+  // deno-lint-ignore no-var
+  var NFRequestContextMap: Map<string, RequestContext>
+}
+
+globalThis.NFRequestContextMap = new Map()
+
 const handler = async (req: Request, context: Context) => {
   const url = new URL(req.url)
   if (url.pathname.startsWith('/_next/static/')) {
@@ -44,18 +56,15 @@ const handler = async (req: Request, context: Context) => {
     city: context.geo.city,
   }
 
-  // The geo object is passed through to the middleware unchanged
-  // so we're smuggling the Request and Netlify context object inside it
-
-  Object.defineProperty(geo, '__nf_context', {
-    value: context,
-    enumerable: false,
-  })
-
-  Object.defineProperty(geo, '__nf_request', {
-    value: req,
-    enumerable: false,
-  })
+  const requestId = req.headers.get('x-nf-request-id')
+  if (!requestId) {
+    console.error('Missing x-nf-request-id header')
+  } else {
+    globalThis.NFRequestContextMap.set(requestId, {
+      request: req,
+      context,
+    })
+  }
 
   const request: RequestData = {
     headers: Object.fromEntries(req.headers.entries()),
@@ -72,6 +81,10 @@ const handler = async (req: Request, context: Context) => {
   } catch (error) {
     console.error(error)
     return new Response(error.message, { status: 500 })
+  } finally {
+    if (requestId) {
+      globalThis.NFRequestContextMap.delete(requestId)
+    }
   }
 }