Workspaces generate inaccurate c8 coverage reports

[kherock]

Describe the bug

The C8 test coverage provider reports different statistics and inaccurate line numbers when the reporter runs on a workspace. When I preview the HTML report, the code highlighted is about 10 lines offset from where the actual uncovered code is. The column number offset also appear to shift 1 or 2 characters.

Reproduction

Vitest hangs when generating coverage in StackBlitz - I will provide a reproduction of this on GitHub when I have a chance.

System Info

System:
    OS: macOS 12.6.3
    CPU: (10) arm64 Apple M1 Pro
    Memory: 112.97 MB / 16.00 GB
    Shell: 5.8.1 - /bin/zsh
  Binaries:
    Node: 16.19.1 - ~/.local/share/homebrew/bin/node
    Yarn: 1.22.19 - ~/.local/share/homebrew/bin/yarn
    npm: 8.19.3 - ~/.local/share/homebrew/bin/npm
  Browsers:
    Firefox: 102.2.0
    Safari: 16.3
  npmPackages:
    @vitest/coverage-c8: ^0.30.1 => 0.30.1 
    vitest: ^0.30.1 => 0.30.1

Used Package Manager

npm

Validations

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

[github-actions]

Hello @kherock. Please provide a minimal reproduction using a GitHub repository or StackBlitz. Issues marked with need reproduction will be closed if they have no activity within 3 days.

[kherock]

Does this still need a reproduction? I think the linked PR #3226 covers the problems I'm experiencing.

[AriPerkkio]

There was a clear bug in how @vitest/coverage-c8 handles sources maps when workspaces are used. The internal test cases of Vitest were enough to reproduce the issue.

[ocavue]

Here is a reproduction I created. I hope this can help to fix and test the bug

Reproduce Steps:

$ git clone https://github.com/issueset/vitest-workspace-c8-bug
$ cd vitest-workspace-c8-bug
$ pnpm install
$ pnpm run test:c8
$ pnpm run test:istanbul

Open the report html files under coverage/. It's clear that console.log("A3") should never be covered, but the c8 reporter shows that this line is been covered.

[AriPerkkio]

Thanks @ocavue - this is how the reproduction case looks like with the changes of #3226: