There is a hard requirement for an Xcode project with slather.

Swift packages can generate their code coverage from a command-line build using swift test --enable-code-coverage
with the results written to the .build/debug/codecov folder.

That folder contains three files:

• PackageName.json
• default.profdata
• default_build_ID_.profraw

The information can be parsed from the json file easily enough, and converted to the desired output format.