Fork `istanbuljs/istanbuljs` as `@vitest/istanbuljs`

[AriPerkkio]

Clear and concise description of the problem

Vitest's coverage packages rely on istanbuljs organizations monorepo's packages https://github.com/istanbuljs/istanbuljs. This project has existed for ~13 years and is battle-tested by large projects like Jest, nyc, c8 and Vitest.

The project has had limited maintenance for long time. Landing fixes and features has been taking months. Currently we have 3 PRs that we are (/going to be) patching to Vitest:

• feat: support ignore start and ignore stop istanbuljs/istanbuljs#835
• fix: istanbul-lib-source-maps to map functions without closing brace mapping istanbuljs/istanbuljs#837
• fix: use lenient matching for coverage merge when end.column differs istanbuljs/istanbuljs#838

Patching some Istanbul packages is really tricky as they do instanceof checks on runtime. Having two sources for same package fails these checks.

Suggested solution

Fork https://github.com/istanbuljs/istanbuljs as vitest-dev/istanbuljs and publish its packages as @vitest/istanbul-lib-<name> packages. I would expect these packages to live outside of vitest-dev/vitest monorepo.

Alternative

Get someone from Vitest team into Istanbuljs organization and as maintainer of istanbuljs/istanbuljs package. ✋

Additional context

No response

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

[AriPerkkio]

cc. @SimenB - Would Jest benefit of similar fork? It could also live outside vitest-dev organization if needed.