fix: CSS imports in Worker modules causing dev server to crash when starting up (#11404)

* Import CSS in assets playground to cause test failure

* Call pluginContainer.buildStart() for the client environment before making requests

* Add changeset

Author: jamesopstad

.changeset/nasty-jobs-tan.md

@@ -0,0 +1,5 @@
+---
+"@cloudflare/vite-plugin": patch
+---
+
+fix: CSS imports in Worker modules causing dev server to crash when starting up

packages/vite-plugin-cloudflare/playground/assets/src/index.css

@@ -0,0 +1,3 @@
+body {
+	background-color: red;
+}

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

@@ -2,6 +2,8 @@ import html from "./index.html?raw";
 import importedImage from "./imported-image.svg";
 import importedText from "./imported-text.txt?url";
 import inlineImage from "./inline-image.svg?inline";
+// Import CSS to ensure this doesn't cause errors
+import "./index.css";
 
 interface Env {
 	ASSETS: Fetcher;

packages/vite-plugin-cloudflare/src/export-types.ts

@@ -159,6 +159,10 @@ export async function getCurrentWorkerNameToExportTypesMap(
 	viteDevServer: vite.ViteDevServer,
 	miniflare: Miniflare
 ): Promise<Map<string, ExportTypes>> {
+	// Vite's internal CSS plugins rely on `buildStart` being called for the client environment before modules are transformed in server environments
+	// Vite calls this method when initialising the dev server but we need to make requests before that happens
+	await viteDevServer.environments.client.pluginContainer.buildStart();
+
 	const results = await Promise.all(
 		[...resolvedPluginConfig.environmentNameToWorkerMap].map(
 			async ([environmentName, worker]) => {