Stabilizing viteModuleRunner

[sheremet-va]

experimental.viteModuleRunner

• Introduced in 4.1.0-beta.2
• Docs

Vitest has become popular with projects that do not use Vite in their pipeline and don't require any custom transformations of their files. With --strip-types becoming the default in Node.js, we think it makes sense for Vitest to provide a way to opt-out of Vite's module runner and run tests natively (similar to how ava, mocha or node:test work).

import { defineConfig } from 'vitest/config'

export default defineConfig({
  test: {
    experimental: {
      viteModuleRunner: false,
    },
  },
})

Disabling Vite's module runner has a lot of consequences. All transformations will be disabled, including aliases. Vitest won't automatically interop default of ES modules (providing default as a module namespace). All files will be processed natively by your runtime. The goal is to support any server runtime that supports Worker or child_process.

import.meta.env, require, __dirname, __filename will no longer be automatically injected into every file. (Note that we plan to introduce a separate strict option to disable this behaviour even in Vite's module runner). Module mocking and in-source tests still work and are implemented by using Node's sync module hooks - we want to support as many of Vitest's features as possible in this mode.

This is an attempt to experiment and explore a more standard approach to running tests and reduce friction introduced by Vite's module runner.