Use correct host in exchange (#2651)

* Use subdomain

.changeset/happy-grapes-check.md

@@ -0,0 +1,5 @@
+---
+"wrangler": minor
+---
+
+Previously, wrangler dev would not work if the root of your zone wasn't behind Cloudflare. This behaviour has changed so that now only the route which your Worker is exposed on has to be behind Cloudflare.

packages/wrangler/src/create-worker-preview.ts

@@ -109,6 +109,14 @@ function randomId(): string {
 	});
 }
 
+// URLs are often relative to the zone. Sometimes the base zone
+// will be grey-clouded, and so the host must be swapped out for
+// the worker route host, which is more likely to be orange-clouded
+function switchHost(originalUrl: string, host?: string): URL {
+	const url = new URL(originalUrl);
+	url.hostname = host ?? url.hostname;
+	return url;
+}
 /**
  * Generates a preview session token.
  */
@@ -129,9 +137,13 @@ export async function createPreviewSession(
 		abortSignal
 	);
 
-	logger.debug(`-- START EXCHANGE API REQUEST: GET ${exchange_url}`);
+	const switchedExchangeUrl = switchHost(exchange_url, ctx.host).toString();
+
+	logger.debug(`-- START EXCHANGE API REQUEST: GET ${switchedExchangeUrl}`);
 	logger.debug("-- END EXCHANGE API REQUEST");
-	const exchangeResponse = await fetch(exchange_url, { signal: abortSignal });
+	const exchangeResponse = await fetch(switchedExchangeUrl, {
+		signal: abortSignal,
+	});
 	const bodyText = await exchangeResponse.text();
 	logger.debug(
 		"-- START EXCHANGE API RESPONSE:",
@@ -147,16 +159,15 @@ export async function createPreviewSession(
 		token: string;
 		prewarm: string;
 	}>(bodyText);
-
-	const { host } = new URL(inspector_websocket);
-	const query = `cf_workers_preview_token=${token}`;
+	const inspector = new URL(inspector_websocket);
+	inspector.searchParams.append("cf_workers_preview_token", token);
 
 	return {
 		id: randomId(),
 		value: token,
-		host,
-		inspectorUrl: new URL(`${inspector_websocket}?${query}`),
-		prewarmUrl: new URL(prewarm),
+		host: ctx.host ?? inspector.host,
+		inspectorUrl: switchHost(inspector.href, ctx.host),
+		prewarmUrl: switchHost(prewarm, ctx.host),
 	};
 }