vitest-dev/vitest · error

Cannot parse ' ' because "module.stripTypeScriptTypes" is…

Error message

Cannot parse '${url}' because "module.stripTypeScriptTypes" is not supported. TypeScript coverage requires Node.js 22.15 or higher. This is NOT a bug of Vitest.

What it means

When Vite's module runner is disabled for coverage transforms (experimental.viteModuleRunner === false, or the file wasn't transformed by Vite), Vitest falls back to Node's module.stripTypeScriptTypes to strip TS. That API exists only in Node 22.15+, so on older Node processing a .ts/.mts/.cts coverage target it throws — and the message explicitly states this is NOT a Vitest bug.

Solutions

1. Upgrade Node to 22.15 or higher (module.stripTypeScriptTypes is available).
2. Enable the Vite module runner (remove experimental.viteModuleRunner: false).
3. Run Node with --experimental-transform-types (or set NODE_OPTIONS) so the transform mode is available.
4. Avoid TypeScript-only coverage in stripped mode on old Node.

Example fix

// before
node --version # v20.x -> throws
vitest run --coverage

// after
nvm use 22 # >= 22.15
node --experimental-transform-types ./node_modules/vitest/vitest.mjs run --coverage

import { gte } from 'semver'
function nodeSupportsStripTs() {
  return typeof require('module').stripTypeScriptTypes === 'function'
    || gte(process.version, 'v22.15.0')
}
// before TS coverage with viteModuleRunner off: if (!nodeSupportsStripTs()) upgrade Node or enable runner

function supportsStripTypeScriptTypes(): boolean {
  return typeof (require('module').stripTypeScriptTypes) === 'function'
}

When it happens

Trigger: Coverage over TypeScript files with experimental.viteModuleRunner === false (or non-Vite-transformed files) on a Node runtime below 22.15, so module.stripTypeScriptTypes is undefined.

Common situations: Older Node LTS (20.x or early 22); disabling viteModuleRunner for perf/isolation; running TS coverage without --experimental-transform-types.

Related errors

• Cannot parse ' ' because "module.stripTypeScriptTypes" is…
• Cannot parse ' ' because "module.stripTypeScriptTypes" is…
• Cannot parse the module format of
• Custom CoverageProviderModule loaded from
• ${error instanceof Error ? error.message : String(error)}

AI-assisted analysis of vitest-dev/vitest@1fa9837ec2 (2026-08-11). Data as JSON: /api/errors/c814e7fa17d9c3ac. Report an issue: GitHub.

Appendix: source

Thrown at packages/vitest/src/node/coverage.ts:743

  // TODO: should this be abstracted in `project`/`vitest` instead?
  // if we decide to keep `viteModuleRunner: false`, we will need to abstract transformation in both main thread and tests
  // custom --import=module.registerHooks need to be transformed as well somehow
  async transformFile(url: string, project: TestProject, viteEnvironment: string, isTransformedByVite = true): Promise<TransformResult | null | undefined> {
    const config = project.config

    // vite is disabled, should transform manually if possible
    if (config.experimental.viteModuleRunner === false || !isTransformedByVite) {
      const pathname = url.split('?')[0]
      const filename = pathname.startsWith('file://') ? fileURLToPath(pathname) : pathname
      const extension = path.extname(filename)
      const isTypeScript = extension === '.ts' || extension === '.mts' || extension === '.cts'
      if (!isTypeScript) {
        const code = await fs.readFile(filename, 'utf-8')
        return { code, map: null }
      }
      if (!module.stripTypeScriptTypes) {
        throw new Error(`Cannot parse '${url}' because "module.stripTypeScriptTypes" is not supported. TypeScript coverage requires Node.js 22.15 or higher. This is NOT a bug of Vitest.`)
      }
      const isTransform = process.execArgv.includes('--experimental-transform-types')
        || config.execArgv.includes('--experimental-transform-types')
        || process.env.NODE_OPTIONS?.includes('--experimental-transform-types')
        || config.env?.NODE_OPTIONS?.includes('--experimental-transform-types')
      const code = await fs.readFile(filename, 'utf-8')
      return {
        // `transform` mode will inject source maps comment at the end
        code: module.stripTypeScriptTypes(code, { mode: isTransform ? 'transform' : 'strip' }),
        map: null,
      }
    }

    return project.vite.environments[viteEnvironment].transformRequest(url)
  }

  createUncoveredFileTransformer(ctx: Vitest) {
    const projects = new Set([

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