Add an option to collect coverage from `node_modules` package(s)

[OSA413]

Clear and concise description of the problem

So, I want to do an extensive E2E testing for an external package I use. Currently @vitest/coverage-v8 only provides coverage for files that are in the project itself.

Suggested solution

Add an option to the Vite's test config to include and collect coverage of node_modules.

Alternative

c8 has excludeNodeModules option but it seems to only include the files to the report, but it reports incorrect files (probably because of relying on the source maps of the package)

bcoe/c8#250

Additional context

I looks like @vitest/coverage-istanbul doesn't support it neither

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.

[sheremet-va]

v8 coverage currently hardcodes the filter of node_modules:

vitest/packages/coverage-v8/src/index.ts

Line 68 in de4e6aa

if (coverage.url.includes('/node_modules/')) {

So, I want to do an extensive E2E testing for an external package I use.

If you are doing something like that, then you can probably patch Vitest itself locally to enable this.