Ensure path is relative (#699)

* Ensure path is relative

* Add regression test

packages/miniflare/src/workers/core/entry.worker.ts

@@ -40,7 +40,7 @@ function getUserRequest(
 		// If a custom `upstream` was specified, make sure the URL starts with it
 		let path = url.pathname + url.search;
 		// Remove leading slash, so we resolve relative to `upstream`'s path
-		if (path.startsWith("/")) path = path.substring(1);
+		if (path.startsWith("/")) path = `./${path.substring(1)}`;
 		url = new URL(path, upstreamUrl);
 	}
 

packages/miniflare/test/index.spec.ts

@@ -547,7 +547,24 @@ test("Miniflare: fetch mocking", async (t) => {
 		}
 	);
 });
-
+test("Miniflare: custom upstream as origin (with colons)", async (t) => {
+	const upstream = await useServer(t, (req, res) => {
+		res.end(`upstream: ${new URL(req.url ?? "", "http://upstream")}`);
+	});
+	const mf = new Miniflare({
+		upstream: new URL("/extra:extra/", upstream.http.toString()).toString(),
+		modules: true,
+		script: `export default {
+      fetch(request) {
+        return fetch(request);
+      }
+    }`,
+	});
+	t.teardown(() => mf.dispose());
+	// Check rewrites protocol, hostname, and port, but keeps pathname and query
+	const res = await mf.dispatchFetch("https://random:0/path:path?a=1");
+	t.is(await res.text(), "upstream: http://upstream/extra:extra/path:path?a=1");
+});
 test("Miniflare: custom upstream as origin", async (t) => {
 	const upstream = await useServer(t, (req, res) => {
 		res.end(`upstream: ${new URL(req.url ?? "", "http://upstream")}`);