Support import attributes in istanbul coverage

[ghost]

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[hi-ogawa]

The log looks like a babel, but I don't think Vite or Vitest uses babel transform internally. The issue might be in one of your plugins which is running babel.

Can you provide a reproduction?

[ghost]

Hello @hi-ogawa
Here it is your StackBlitz: https://stackblitz.com/edit/vitest-dev-vitest-rwmclk

Some comments:

1. I want to use Vitest Browser Mode.
2. The setup is a Vanilla JavaScript environment, without transpilations.
3. I wanted to use "@vitest/coverage-v8" instead of "@vitest/coverage-istanbul". However, unfortunately, Vitest Browser Mode requires "@vitest/coverage-istanbul". =/

Error message:

1. Run the script "test:run". It runs tests in Vitest Browser Mode.
2. Although the test passes, the console complains with a big error, reproduced after this line. It suggests to install babel, but that is not necessary and not wanted.

00:09:00 [vite] Pre-transform error: /address/file.json: Support for the experimental syntax 'importAttributes' isn't currently enabled (1:61):

Add @babel/plugin-syntax-import-attributes (https://github.com/babel/babel/tree/main/packages/babel-plugin-syntax-import-attributes) to the 'plugins' section of your Babel config 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=/address/file.json
See https://babeljs.io/docs/configuration#print-effective-configs for more info.

3. Vite and Vitest work well with json imports, so I don't see why Vitest Browser Mode should complain about json imports. Although it is a specification in progress, it is native.

I expect this error to be gone. In other words: I expect Vitest Browser Mode to support importing .json files.

[hi-ogawa]

Thanks for the reproduction. Yeah, I couldn't find babel anywhere in vite, vitest or vitest browser, but indeed there's one in @vitest/coverage-istanbul.

It looks like a minimal repro is to run @vitest/coverage-istanbul with import/assert/with somewhere in the code. https://github.com/hi-ogawa/reproductions/tree/main/vitest-coverage-babel
https://stackblitz.com/github/hi-ogawa/reproductions/tree/main/vitest-coverage-babel?file=README.md

This could be a bug or probably just an unfortunate limitation, so you might really need to deal with babel yourself.

[AriPerkkio]

This is the Istanbul part using Babel that Vitest uses: https://github.com/istanbuljs/istanbuljs/blob/main/packages/istanbul-lib-instrument/src/instrumenter.js

Getting new improvements on Istanbul packages can be really slow - even impossible. Maybe we need to patch istanbul-lib-instrument and bundle it in @vitest/coverage-istanbul.