fix: include uncovered files in report when using --all with --include

[wellwelwel]

Checklist

• npm test, tests passing
• npm run test:snap (to update the snapshot)
• tests and/or benchmarks are included
• documentation is changed or added

---

Fixes #588.

In lib/report.js, the _normalizeProcessCov method adds files to fileIndex before checking shouldInstrument():

if (/^file:\/\//.test(v8ScriptCov.url)) {
  // ...
    v8ScriptCov.url = fileURLToPath(v8ScriptCov.url)
    fileIndex.add(v8ScriptCov.url) //    added unconditionally
  // ...
if ((!this.omitRelative || isAbsolute(v8ScriptCov.url))) {
  if (this.excludeAfterRemap || this._shouldInstrument(v8ScriptCov.url)) {
    result.push(v8ScriptCov) //          only added to result if passes filter
  }
}

Then:

• V8 loads, for example, lib/results_stream.js during execution (via require() chain)
• fileIndex.add(v8ScriptCov.url) is called unconditionally
• shouldInstrument() returns false, so the file is not added to result
• _includeUncoveredFiles finds the file via glob, but fileIndex.has() is true, so it's skipped ❌
• The file is absent from both V8 results and uncovered files

---

The fix moves fileIndex.add() to inside the shouldInstrument block, so only files that actually pass the filter are tracked.

---

About the test approach

The test uses createReport and _normalizeProcessCov directly instead of the spawnSync + matchSnapshot pattern used in most integration tests.

Since test-exclude's globSync internally calls shouldInstrument on every file it returns, the paths that fail shouldInstrument in _normalizeProcessCov won't collide with the paths from globSync in _includeUncoveredFiles. Because of that, a regular integration test would pass with or without the fix, so I couldn't find a way to catch a regression through the CLI alone, for example: wellwelwel#1 (comment).

By calling _normalizeProcessCov directly with fake V8 coverage entries, we can verify that fileIndex is only populated with files that pass shouldInstrument.

Note

I can also move this test to a separate file for unit tests if that makes more sense 🙋🏻‍♂️

[wellwelwel]

Just as a proof of concept, here is the current test failure without the fix applied:

2 failing

1) c8
     --all
       should only track files that pass shouldInstrument in fileIndex:

    AssertionError: expected true to equal false
    + expected - actual

    -true
    +false
    
    at Context.<anonymous> (test/integration.js:543:44)
    at process.processImmediate (node:internal/timers:504:21)

2) c8 mergeAsync
     --all
       should only track files that pass shouldInstrument in fileIndex:

    AssertionError: expected true to equal false
    + expected - actual

    -true
    +false
    
    at Context.<anonymous> (test/integration.js:543:44)
    at process.processImmediate (node:internal/timers:504:21)