fix(vitest-pool-workers): fetchMock support on auxiliary worker (#8239)

Author: edmundhung

.changeset/huge-pears-tickle.md

@@ -0,0 +1,5 @@
+---
+"miniflare": patch
+---
+
+fix: allow the `fetchMock` option to be parsed upfront before passing it to Miniflare

packages/miniflare/src/plugins/core/index.ts

@@ -163,6 +163,11 @@ export const CoreOptionsSchema = CoreOptionsSchemaInput.transform((value) => {
 				"Only one of `outboundService` or `fetchMock` may be specified per worker"
 			);
 		}
+
+		// The `fetchMock` option is used to construct the `outboundService` only
+		// Removing it from the output allows us to re-parse the options later
+		// This allows us to validate the options and then feed them into Miniflare without issue.
+		value.fetchMock = undefined;
 		value.outboundService = (req) => fetch(req, { dispatcher: fetchMock });
 	}
 	return value;

packages/miniflare/test/index.spec.ts

@@ -33,6 +33,8 @@ import {
 	Miniflare,
 	MiniflareCoreError,
 	MiniflareOptions,
+	parseWithRootPath,
+	PLUGINS,
 	ReplaceWorkersTypes,
 	Response,
 	viewToBuffer,
@@ -1108,15 +1110,27 @@ test("Miniflare: fetch mocking", async (t) => {
 	const origin = fetchMock.get("https://example.com");
 	origin.intercept({ method: "GET", path: "/" }).reply(200, "Mocked response!");
 
-	const mf = new Miniflare({
+	const mfOptions: MiniflareOptions = {
 		modules: true,
 		script: `export default {
 			async fetch() {
 				return fetch("https://example.com/");
 			}
 		}`,
 		fetchMock,
-	});
+	};
+	const resultOptions = {} as MiniflareOptions;
+
+	// Verify that options with `fetchMock` can be parsed first before passing to Miniflare
+	// Regression test for https://github.com/cloudflare/workers-sdk/issues/5486
+	for (const plugin of Object.values(PLUGINS)) {
+		Object.assign(
+			resultOptions,
+			parseWithRootPath("", plugin.options, mfOptions)
+		);
+	}
+
+	const mf = new Miniflare(resultOptions);
 	t.teardown(() => mf.dispose());
 	const res = await mf.dispatchFetch("http://localhost");
 	t.is(await res.text(), "Mocked response!");