Vitest introduced a few breaking changes in 0.34.0: https://github.com/vitest-dev/vitest/releases/tag/v0.34.0

Simply upgrading Vitest to 0.34 in generated project will cause error TS2345 in vitest.config.ts:

Argument of type 'UserConfig & Promise<UserConfig> & UserConfigFnObject & UserConfigExport' is not assignable to parameter of type 'never'.
  Type 'UserConfig & Promise<UserConfig> & UserConfigFnObject' is not assignable to type 'never'.

Here's my workaround (not pretty at all):

-import { mergeConfig, defineConfig } from 'vite'
+import { mergeConfig, defineConfig, UserConfig } from 'vite'

-export default mergeConfig(
+export default mergeConfig<UserConfig, UserConfig>(

Then I got TS2769 due to the breaking change of transformMode mentioned in Vitest 0.34.0 changelog:

No overload matches this call.
  The last overload gave the following error.

Hopefully, someone can help update Vitest to 0.34