vitest coverage-istanbul does not work with workspaces and SvelteKit

Describe the bug

In a monorepo with a simple SvelteKit app, running coverage with @vitest/coverage-istanbul does not work. Tests pass but collecting coverage fails with the following error:

SyntaxError: /Users/ernest/Projects/Repros/vitest-workspaces-istanbul/packages/web/src/routes/+page.svelte: Support for the experimental syntax 'jsx' isn't currently enabled (1:1):

> 1 | <h1>Welcome to SvelteKit</h1>
    | ^
  2 | <p>Visit <a href="https://kit.svelte.dev">kit.svelte.dev</a> to read the documentation</p>
  3 |

Add @babel/preset-react (https://github.com/babel/babel/tree/main/packages/babel-preset-react) to the 'presets' section of your Babel config to enable transformation.
If you want to leave it as-is, add @babel/plugin-syntax-jsx (https://github.com/babel/babel/tree/main/packages/babel-plugin-syntax-jsx) to the 'plugins' section to enable parsing.

If you already added the plugin for this syntax to your config, it's possible that your config isn't being loaded.
You can re-run Babel with the BABEL_SHOW_CONFIG_FOR environment variable to show the loaded configuration:
        npx cross-env BABEL_SHOW_CONFIG_FOR=/Users/ernest/Projects/Repros/vitest-workspaces-istanbul/packages/web/src/routes/+page.svelte <your build command>
See https://babeljs.io/docs/configuration#print-effective-configs for more info.

1  |  <h1>Welcome to SvelteKit</h1>
   |  ^
2  |  <p>Visit <a href="https://kit.svelte.dev">kit.svelte.dev</a> to read the documentation</p>
3  |

Works fine with @vitest/coverage-v8 but I need istanbul (required by @cloudflare/vitest-pool/workers)

Reproduction

Clone repo
Install dependencies (bun install)
Run test script (bun run test) - everything passes
Run coverage script (bun run coverage)

System Info

System:
    OS: macOS 14.5
    CPU: (8) arm64 Apple M1
    Memory: 40.45 MB / 16.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 20.12.2 - ~/Library/Caches/fnm_multishells/86163_1717766938803/bin/node
    npm: 10.5.0 - ~/Library/Caches/fnm_multishells/86163_1717766938803/bin/npm
    pnpm: 8.9.0 - ~/Library/pnpm/pnpm
    bun: 1.1.12 - ~/.bun/bin/bun
  Browsers:
    Chrome: 125.0.6422.77
    Edge: 125.0.2535.92
    Safari: 17.5
  npmPackages:
    @vitest/coverage-istanbul: 1.5.0 => 1.5.0 
    vitest: 1.5.0 => 1.5.0

Used Package Manager

npm

Validations

[X] Follow our Code of Conduct
[X] Read the Contributing Guidelines.
[X] Read the docs.
[X] Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
[X] Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
[X] The provided reproduction is a minimal reproducible example of the bug.

Jun 07 '24 13:06 Ernxst

As work-around for now you can set coverage.all: false or configure Svelte plugin in the root vitest.config.ts.

I think this is caused by the root vitest.config.ts not having Svelte Vite plugin, and it fails when transforming uncovered Svelte files here:

https://github.com/vitest-dev/vitest/blob/7cbd943c7bd37ad666dce31537037a53bfdec7cd/packages/coverage-istanbul/src/provider.ts#L304

Jun 09 '24 09:06 AriPerkkio

I'd rather have coverage for all my source files so I went with adding the Svelte plugin to the root vitest.config.ts. It worked in the repro but in my actual project it doesn't - I have an api package which uses @cloudflare/vitest-pool-workers and the api tests fail with:

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯ Unhandled Errors ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯

Vitest caught 1 unhandled error during the test run.
This might cause false positive tests. Resolve unhandled errors to make sure your tests are not affected.

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯ Unhandled Error ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯
TypeError: Cannot use require() to import an ES Module.
 ❯ node_modules/chai/lib/chai/utils/inspect.js node_modules/chai/index.mjs%3Fmf_vitest_no_cjs_esm_shim:217:17
 ❯ __require node_modules/chai/index.mjs%3Fmf_vitest_no_cjs_esm_shim:8:50
 ❯ node_modules/chai/lib/chai/utils/objDisplay.js node_modules/chai/index.mjs%3Fmf_vitest_no_cjs_esm_shim:235:19
 ❯ __require node_modules/chai/index.mjs%3Fmf_vitest_no_cjs_esm_shim:8:50
 ❯ node_modules/chai/lib/chai/utils/getMessage.js node_modules/chai/index.mjs%3Fmf_vitest_no_cjs_esm_shim:262:22
 ❯ __require node_modules/chai/index.mjs%3Fmf_vitest_no_cjs_esm_shim:8:50
 ❯ node_modules/chai/lib/chai/utils/index.js node_modules/chai/index.mjs%3Fmf_vitest_no_cjs_esm_shim:749:26
 ❯ __require node_modules/chai/index.mjs%3Fmf_vitest_no_cjs_esm_shim:8:50
 ❯ node_modules/chai/lib/chai.js node_modules/chai/index.mjs%3Fmf_vitest_no_cjs_esm_shim:2725:17
 ❯ __require node_modules/chai/index.mjs%3Fmf_vitest_no_cjs_esm_shim:8:50

When running vitest from the monorepo root - the tests pass when I run it from the packages/api directory. I created a feature/api branch in the repro and found the same issue there with a minimal setup. After some investigation, it seems that the loupe package chai imports has invalid ESM exports (see this issue and the PR). Removing the module field in its package.json fixes everything so I'm not sure whether this is a vitest issue, a chai issue, a loupe issue or a vitest-pool-workers issue as everything works perfectly when I don't add the Svelte plugin to the root vitest.config.ts.

Jun 09 '24 11:06 Ernxst

After some more testing, it seems adding the plugin to the root breaks anything that doesn't have exactly the correct package exports. For example, I have a package using unplugin-icons and running coverage on it now fails with:

Error: No known conditions for "./types/svelte" specifier in "unplugin-icons" package

Looking in the package.json of the module, I see it has the following export:

"./types/svelte": {
  "types": "./types/svelte.d.ts"
}

With no import condition which sounds reasonable since it's for types only. However, it breaks because of this so the fix is to add "import": "./types/svelte.d.ts". Next, I have a package which uses msw and coverage now fails with:

Error: No known conditions for "./browser" specifier in "msw" package

Which has the following package.json export:

 "./browser": {
    "types": "./lib/browser/index.d.ts",
    "browser": {
      "require": "./lib/browser/index.js",
      "import": "./lib/browser/index.mjs"
    },
    "node": null,
    "require": "./lib/browser/index.js",
    "import": "./lib/browser/index.mjs",
    "default": "./lib/browser/index.js"
}

And this is fixed by simply moving the import condition up, above the browser condition. I doubt patching every failing package.json is the solution here

Jun 09 '24 12:06 Ernxst

I just want to add that this is documented: https://vitest.dev/guide/workspace.html#coverage

Jun 11 '24 14:06 sheremet-va