Fix next(param) in Pages Plugins (#2789)

.changeset/strong-stingrays-relate.md

@@ -0,0 +1,5 @@
+---
+"wrangler": patch
+---
+
+fix: Support overriding the next URL in subsequent executions with `next("/new-path")` from within a Pages Plugin

fixtures/pages-functions-app/public/here.html

@@ -0,0 +1 @@
+<h1>Successful!</h1>

fixtures/pages-functions-app/tests/index.test.ts

@@ -137,6 +137,16 @@ describe.concurrent("Pages Functions", () => {
 			const text = await response.text();
 			expect(text).toContain("I'm a fixed response");
 		});
+
+		it("should support proxying through to next(request)", async ({
+			expect,
+		}) => {
+			const response = await fetch(
+				`http://${ip}:${port}/mounted-plugin/proxy-me-somewhere-else`
+			);
+			const text = await response.text();
+			expect(text).toContain("Successful!");
+		});
 	});
 
 	describe.concurrent("can import static assets", () => {

fixtures/pages-plugin-example/functions/proxy-me-somewhere-else.ts

@@ -0,0 +1 @@
+export const onRequest = ({ next }) => next("/here");

packages/wrangler/templates/pages-template-plugin.ts

@@ -133,15 +133,19 @@ export default function (pluginArgs: unknown) {
 		const handlerIterator = executeRequest(request, relativePathname);
 		const pluginNext = async (input?: RequestInfo, init?: RequestInit) => {
 			if (input !== undefined) {
-				request = new Request(input, init);
+				let url = input;
+				if (typeof input === "string") {
+					url = new URL(input, request.url).toString();
+				}
+				request = new Request(url, init);
 			}
 
 			const result = handlerIterator.next();
 			// Note we can't use `!result.done` because this doesn't narrow to the correct type
 			if (result.done === false) {
 				const { handler, params, path } = result.value;
 				const context = {
-					request,
+					request: new Request(request.clone()),
 					functionPath: workerContext.functionPath + path,
 					next: pluginNext,
 					params,
@@ -157,7 +161,7 @@ export default function (pluginArgs: unknown) {
 
 				return cloneResponse(response);
 			} else {
-				return next();
+				return next(request);
 			}
 		};