fix: Don't return promises from unlisted scripts that do not have an async main function

packages/wxt/src/utils/__tests__/define-unlisted-script.test.ts

@@ -21,4 +21,22 @@ describe('defineUnlistedScript', () => {
 
     expect(actual).toEqual({ main });
   });
+
+  it('should return the result without awaiting for synchronous main functions', () => {
+    const main = vi.fn(() => 'test');
+
+    const actual = defineUnlistedScript(main);
+
+    expect(actual).toEqual({ main });
+    expect(actual.main()).eq('test');
+  });
+
+  it('should return a promise of a result for async main functions', async () => {
+    const main = vi.fn(() => Promise.resolve('test'));
+
+    const actual = defineUnlistedScript(main);
+
+    expect(actual).toEqual({ main });
+    await expect(actual.main()).resolves.toEqual('test');
+  });
 });

packages/wxt/src/virtual/unlisted-script-entrypoint.ts

@@ -2,17 +2,37 @@ import definition from 'virtual:user-unlisted-script-entrypoint';
 import { logger } from '../utils/internal/logger';
 import { initPlugins } from 'virtual:wxt-plugins';
 
-const result = (async () => {
+const result = (() => {
   try {
     initPlugins();
-    return await definition.main();
+  } catch (err) {
+    logger.error(
+      `Failed to initialize plugins for "${import.meta.env.ENTRYPOINT}"`,
+      err,
+    );
+    throw err;
+  }
+  let result;
+  try {
+    result = definition.main();
+
+    if (result instanceof Promise) {
+      result = (result as Promise<any>).catch((err) => {
+        logger.error(
+          `The unlisted script "${import.meta.env.ENTRYPOINT}" crashed on startup!`,
+          err,
+        );
+        throw err;
+      });
+    }
   } catch (err) {
     logger.error(
       `The unlisted script "${import.meta.env.ENTRYPOINT}" crashed on startup!`,
       err,
     );
     throw err;
   }
+  return result;
 })();
 
 // Return the main function's result to the background when executed via the