Vitest 4/Vite 8 breaks vitest coverage

[aarongoldenthal]

What versions & operating system are you using?

System:
OS: Windows 11 10.0.26200
CPU: (20) x64 Intel(R) Core(TM) Ultra 7 265F
Memory: 37.17 GB / 63.71 GB
Binaries:
Node: 24.14.0 - C:\Program Files\nodejs\node.EXE
npm: 11.9.0 - C:\Program Files\nodejs\npm.CMD
npmPackages:
@cloudflare/vitest-pool-workers: ^0.13.3 => 0.13.3
wrangler: ^4.76.0 => 4.76.0

also....

System:
OS: Linux 6.6 Debian GNU/Linux 12 (bookworm) 12 (bookworm)
CPU: (20) x64 Intel(R) Core(TM) Ultra 7 265F
Memory: 30.39 GB / 31.20 GB
Container: Yes
Shell: 5.2.15 - /bin/bash
Binaries:
Node: 24.14.0 - /usr/local/bin/node
Yarn: 1.22.22 - /usr/local/bin/yarn
npm: 11.9.0 - /usr/local/bin/npm
npmPackages:
@cloudflare/vitest-pool-workers: ^0.13.3 => 0.13.3
wrangler: ^4.76.0 => 4.76.0

Please provide a link to a minimal reproduction

https://github.com/aarongoldenthal/wrangler-vite-v8-coverage-test

Describe the Bug

Running vitest with coverage (istanbul) throws the following error and executes no tests:

TypeError: template is not a function
 ❯ requireVisitor node_modules/@vitest/coverage-istanbul/dist/provider.js:1024:40
    1022|      LogicalExpression: entries(coverLogicalExpression)
    1023|  };
    1024|  const globalTemplateAlteredFunction = template(`
       |                                        ^
    1025|         var Function = (function(){}).constructor;
    1026|         var global = (new Function(GLOBAL_COVERAGE_SCOPE))();
 ❯ requireInstrumenter node_modules/@vitest/coverage-istanbul/dist/provider.js:1325:25
 ❯ requireSrc$1 node_modules/@vitest/coverage-istanbul/dist/provider.js:1495:23
 ❯ node_modules/@vitest/coverage-istanbul/dist/provider.js:1518:18
 ❯ VitestModuleEvaluator._runInlinedModule node_modules/vitest/dist/module-evaluator.js:206:4
 ❯ ServerModuleRunner.directRequest node_modules/vite/dist/node/module-runner.js:1243:59
 ❯ ServerModuleRunner.cachedRequest node_modules/vite/dist/node/module-runner.js:1150:73
 ❯ Object.getProvider node_modules/@vitest/coverage-istanbul/dist/index.js:31:40
 ❯ Vitest.initCoverageProvider node_modules/vitest/dist/chunks/cli-api.DuT9iuvY.js:13181:28
 ❯ node_modules/vitest/dist/chunks/cli-api.DuT9iuvY.js:13302:6

The same tests run nominally when running without coverage, or with coverage and removing the cloudflareTest plugin from the vitest config.

This appears to be related to #12984.

Please provide any relevant error logs

No response

[BenjaminPrice]

I'm running into the same issue. It looks like it may be a Istanbul related issue relating to CJS.

[aarongoldenthal]

It appears to be this change in Vite 8. When Vitest is run with the cloudflareTest plugin from @cloudflare/vitest-pool-workers, then @babel/core imported by @vitest/coverage-istanbul no longer has a default import in node_modules/@vitest/coverage-istanbul/dist/provider.js

// require$$0$3 is undefined
import require$$0$3 from '@babel/core';

If that's changed to the following, everything runs nominally:

import * as require$$0$3 from '@babel/core';

[mraerino]

looks like this is fixed here, but the fix is unreleased: vitest-dev/vitest#9939

[petebacondarwin]

Yes - closing as a duplicate of #12951, which will also be closed when the new vitest package is released.