Set preserveEntrySignatures: "strict" for Worker environments (#10544)

* Updated worker playground to fail

* Add preserveEntrySignatures: 'strict'

* Add changeset

Author: jamesopstad

.changeset/bumpy-garlics-call.md

@@ -0,0 +1,5 @@
+---
+"@cloudflare/vite-plugin": patch
+---
+
+Set `preserveEntrySignatures: "strict"` for Worker environments. This ensures that no additional exports are added to the entry module.

packages/vite-plugin-cloudflare/playground/worker/__tests__/worker.spec.ts

@@ -17,6 +17,10 @@ test("basic hello-world functionality", async () => {
 	);
 });
 
+test("preserves entry signatures", async () => {
+	expect(serverLogs.info.join()).toContain("__preserves-entry-signatures__");
+});
+
 test("basic dev logging", async () => {
 	expect(serverLogs.info.join()).toContain("__console log__");
 	expect(serverLogs.errors.join()).toContain("__console error__");

packages/vite-plugin-cloudflare/playground/worker/src/a.ts

@@ -0,0 +1 @@
+export const a = "__preserves-entry-signatures__";

packages/vite-plugin-cloudflare/playground/worker/src/b.ts

@@ -0,0 +1,5 @@
+import { a } from "./a";
+
+export function fn() {
+	console.log(a);
+}

packages/vite-plugin-cloudflare/playground/worker/src/index.ts

@@ -1,3 +1,5 @@
+import { a } from "./a";
+
 export default {
 	async fetch(request) {
 		const url = new URL(request.url);
@@ -6,6 +8,10 @@ export default {
 			return new Response(request.headers.get("X-Forwarded-Host"));
 		}
 
+		console.log(a);
+		const { fn } = await import("./b");
+		fn();
+
 		console.log("__console log__");
 		console.warn("__console warn__");
 		console.error("__console error__");

packages/vite-plugin-cloudflare/src/cloudflare-environment.ts

@@ -168,6 +168,8 @@ export function createCloudflareEnvironmentOptions({
 			ssr: true,
 			rollupOptions: {
 				input: workerConfig.main,
+				// workerd checks the types of the exports so we need to ensure that additional exports are not added to the entry module
+				preserveEntrySignatures: "strict",
 				// rolldown-only option
 				...("rolldownVersion" in vite ? ({ platform: "neutral" } as any) : {}),
 			},