populate env var earlier to support vite preview

Author: edmundhung

packages/vite-plugin-cloudflare/src/plugin-config.ts

@@ -112,6 +112,14 @@ export function resolvePluginConfig(
 		experimental: pluginConfig.experimental ?? {},
 	};
 	const root = userConfig.root ? path.resolve(userConfig.root) : process.cwd();
+	const buildTimeEnv = vite.loadEnv(viteEnv.mode, root, [
+		"CLOUDFLARE_",
+		"WRANGLER_",
+	]);
+
+	// Merge the loaded env variables into process.env so that they are available to
+	// wrangler when it loads the worker configuration files.
+	Object.assign(process.env, buildTimeEnv);
 
 	if (viteEnv.isPreview) {
 		return {
@@ -122,15 +130,6 @@ export function resolvePluginConfig(
 	}
 
 	const configPaths = new Set<string>();
-	const buildTimeEnv = vite.loadEnv(viteEnv.mode, root, [
-		"CLOUDFLARE_",
-		"WRANGLER_",
-	]);
-
-	// Merge the loaded env variables into process.env so that they are available to
-	// wrangler when it loads the worker configuration files.
-	Object.assign(process.env, buildTimeEnv);
-
 	const cloudflareEnv = buildTimeEnv.CLOUDFLARE_ENV;
 	const entryWorkerConfigPath = getValidatedWranglerConfigPath(
 		root,