--scope-output does not work

[gogolon]

Sometimes coverage is gathered from external packages even when --scope-output flag is used and set to the name of the app's package.

Reproduction

1. Create a new dart project with dart create minimal-sample
2. Add equatable package: dart pub add equatable
3. Replace the code inside lib/minimal_sample.dart with the code below:

import 'package:equatable/equatable.dart';

class SomeClass with EquatableMixin {
  @override
  List<Object?> get props => [];
}

int calculate() {
  return 6 * 7;
}

4. run

dart run --pause-isolates-on-exit --disable-service-auth-codes --enable-vm-service=8181 test &
dart pub global run coverage:collect_coverage --wait-paused --uri=http://127.0.0.1:8181/ -o coverage/coverage.json --resume-isolates --scope-output=minimal_sample

After performing the steps above, the generated coverage/coverage.json looks like this:

{
  "type": "CodeCoverage",
  "coverage": [
    {
      "source": "package:minimal_sample/minimal_sample.dart",
      "script": {
        "type": "@Script",
        "fixedId": true,
        "id": "libraries/1/scripts/package%3Aminimal_sample%2Fminimal_sample.dart",
        "uri": "package:minimal_sample/minimal_sample.dart",
        "_kind": "library"
      },
      "hits": [
        4,
        0,
        5,
        0,
        8,
        1,
        9,
        1
      ]
    },
    {
      "source": "package:equatable/src/equatable_mixin.dart",
      "script": {
        "type": "@Script",
        "fixedId": true,
        "id": "libraries/1/scripts/package%3Aequatable%2Fsrc%2Fequatable_mixin.dart",
        "uri": "package:equatable/src/equatable_mixin.dart",
        "_kind": "library"
      },
      "hits": [
        16,
        0,
        18,
        0,
        21,
        0,
        22,
        0,
        23,
        0,
        26,
        0,
        27,
        0,
        29,
        0,
        31,
        0,
        32,
        0,
        33,
        0,
        34,
        0,
        35,
        0,
        37,
        0,
        38,
        0,
        39,
        0
      ]
    }
  ]
}

I use Dart SDK 3.3.3.

[liamappelbe]

There are 2 ways of filtering the output, collect_coverage's --scope-output flag, and format_coverage's --report-on flag. scope-output is passed to the VM, and used to filter which libraries are collected. Due to the way mixins work (essentially copy/pasting their code into the child class), when it reports on SomeClass, it also reports on EquatableMixin. report-on works purely within package:coverage, and doesn't understand language constructs like mixins, so it will filter out EquatableMixin.

I can probably fix the VM logic to be stricter about applying the filters to mixins. In the meantime, you can use --report-on to further filter the result.

[liamappelbe]

Took another look at how the source report is implemented in the VM, and it's not going to be easy to fix it in there. Better to apply the filters to the report returned by the VM (in addition to passing the filters to the VM).