Add a tool to find uncovered files

[liamappelbe]

If a file is not imported by the tests, it will not be compiled, so won't be mentioned in the source report. The compiler/VM won't be aware that the file even exists. This means that entire files can be uncovered without affecting the coverage report.

We could add a tool (or an option in an existing tool) that searches for all the .dart files in the package directory and reports any that are not mentioned in the coverage data.

The tool would need some filtering options, because it's common to have scripts that are not intended to be tested or used outside of the package (eg scripts in the tool directory). Maybe by default it should only look in the src subdirectory.

The tool will also need to support workspaces when they are added.

Context: flutter/flutter#145609

[khushi-hura]

hey @liamappelbe! As far as I can understand, this issue focusses on developing a tool which could search for some uncovered files during the test of the project. Could you please correct me if I am wrong or could you please ellaborate the issue?
I think I can work on it, will be sharing my approach in a few days!
Your response will be thankful :)

[liamappelbe]

hey @liamappelbe! As far as I can understand, this issue focusses on developing a tool which could search for some uncovered files during the test of the project. Could you please correct me if I am wrong or could you please ellaborate the issue? I think I can work on it, will be sharing my approach in a few days! Your response will be thankful :)

Yep, that's the basic idea. Thinking a bit more about the design, it probably shouldn't be a separate tool. Instead it should be baked into the formatter. Add an optional parameter to FileHitMapsFormatter.formatLcov (and probably also FileHitMapsFormatter.prettyPrint) that controls the behavior of this feature.

The API could look something like this:

extension FileHitMapsFormatter on Map<String, HitMap> {
  String formatLcov(
    Resolver resolver, {
    String? basePath,
    List<String>? reportOn,
    Set<Glob>? ignoreGlobs,
    Function<bool(String)>? includeUncovered,  // <- new option
  }) {

If includeUncovered is null the behavior should stay the same as it is now. Otherwise it should be a function that returns whether the given path should be included in the repot if it's not covered. We'll also need a way for users to easily specify a sensible default behavior (eg only searching in the lib/src directory), so maybe add static function that does this and users can pass that for the typical behavior. That's just an idea though, so feel free to propose other APIs.

Once that's working you'll need to add a flag for it to bin/format_coverage.dart, and bin/test_with_coverage.dart. Once it's landed and published I'll add the option to Flutter. That way we'll get the new behavior across all the Dart and Flutter coverage use cases.

[khushi-hura]

Okay got that, will try working and let u know if I need any further help!