Expose sourceFinder in @vite/coverage-v8 createContext

[teoeter]

Clear and concise description of the problem

Angular 20 Vitest has an issue where the src paths are not resolved correctly by istanbul-lib-coverage, which is used by vitest/coverage-v8 so the coverage report in the default angular project doesn't work.

See: angular/angular-cli#30511

A fix is straightforward using the sourceFinder property of the createContext function. However, for it to work, the property needs to be transferred from the options to the createContext configuration.

Suggested solution

See PR: #8325

Explanation:

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

Line 115 in 87245a5

const context = libReport.createContext({

so my suggestion is to add sourceFinder as an option:

    const context = libReport.createContext({
      dir: this.options.reportsDirectory,
      coverageMap,
      watermarks: this.options.watermarks,
      sourceFinder: this.options.sourceFinder
    })

This would allow the angular/cli builder to rewrite the path that is causing the following issue:

Unable to lookup source: /..../angular20/dist/test-out/20250718T220622393Z-47be11c7/src/app/app.ts 
(ENOENT: no such file or directory, 
open '/..../angular20/dist/test-out/20250718T220622393Z-47be11c7/src/app/app.ts')

to replace it with: /..../angular20/src/app/app.ts - remove dist/test-out/20250718T220622393Z-47be11c7/

I tested it, and it solves the issue. Angular 20 with Vitest is able to generate proper code coverage reports without the error.

Alternative

Is there an alternative approach or a config I'm missing?

a custom reporter / provider could be used but that is not as nice as the sourceFinder.
also maybe the source folder where the src file are can be configurated / it's maybe a path config issue

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]

This sounds like source map issue. Solving it via sourceFinder works but is not the correct way to fix it.

Can you provide minimal repro?

[teoeter]

Basically:

ng new

and follow:
https://angular.dev/guide/testing/unit-tests
set:
codeCoverage: true,  
in angular.json

generates a faulty istanbul coverage html report ( the CLI one is correct).

Here is a pre-configured project according to the tutorial (minimal reproduction):

https://github.com/teoeter/angular-vitest

npm i 
ng test

should generate a folder named coverage\ going to app.html will show the error.

the angular vitest configuration is in:

node_modules/@angular/build/src/builders/unit-test/builder.js

source code:
https://github.com/angular/angular-cli/blob/main/packages/angular/build/src/builders/unit-test/builder.ts

[teoeter]

The issue could be in the line:

    include: [`${toPosixPath(path.relative(workspaceRoot, outputPath))}/**`],

https://github.com/angular/angular-cli/blob/7595e1f8887bafd344ec939e647e3fca8bbd98be/packages/angular/build/src/builders/unit-test/builder.ts#L411

this translates to: dist/test-out/20250720T213327968Z-00fd3980/**. (macos)

just for testing/experiment if that is corrected to src:

  include: [`src/**`],

after the change the report works, but ofc the code coverge is not correct

Compared to the prev configuration:

but that generates the error in the html report