Return copy of entry URL from Miniflare#ready (#671)

There are cases where mutating the URL returned from
`Miniflare#ready` may be desirable, e.g. changing the protocol to
`ws:` and using the `ws` module to establish a WebSocket connection.
Previously, doing this would break Miniflare's `dispatchFetch`, as
the returned URL was Miniflare's own internal reference. This change
makes sure we return a copy.

packages/miniflare/src/index.ts

@@ -1071,7 +1071,8 @@ export class Miniflare {
 		// called by `#init()`, and `#initPromise` doesn't resolve until `#init()`
 		// returns.
 		assert(this.#runtimeEntryURL !== undefined);
-		return this.#runtimeEntryURL;
+		// Return a copy so external mutations don't propagate to `#runtimeEntryURL`
+		return new URL(this.#runtimeEntryURL.toString());
 	}
 	get ready(): Promise<URL> {
 		return this.#waitForReady();

packages/miniflare/test/index.spec.ts

@@ -77,6 +77,21 @@ test("Miniflare: validates options", async (t) => {
 	);
 });
 
+test("Miniflare: ready returns copy of entry URL", async (t) => {
+	const mf = new Miniflare({
+		port: 0,
+		modules: true,
+		script: "",
+	});
+	t.teardown(() => mf.dispose());
+
+	const url1 = await mf.ready;
+	url1.protocol = "ws:";
+	const url2 = await mf.ready;
+	t.not(url1, url2);
+	t.is(url2.protocol, "http:");
+});
+
 test("Miniflare: keeps port between updates", async (t) => {
 	const opts: MiniflareOptions = {
 		port: 0,