### Current problem A common setup for repos is to use the src layout discussed [here](https://packaging.python.org/en/latest/discussions/src-layout-vs-flat-layout/). Currently, for src layouts, we could set `--source-roots` to be `src` when calling `pylint` with the source. This avoids the legacy issue of import discovery if there are namespace packages. One issue with the solution is that, if the user wants to also lint say the `test` directory in the repo, this solution does not work. That is because currently if a source root doesn't contain the module or directory passed to pylint for linting, it will fallback to legacy behavior of walking the directory. This will lead to import errors when linting the test files. ### Desired solution Alter the fallback logic when source-root containing module directory is not found [here](https://github.com/pylint-dev/pylint/blob/4c5393f2e5d1ccc35501bb072ac09e5b8301ccdc/pylint/lint/expand_modules.py#L39) to return a list of `source-roots`. This requires changing the function return type to be a `Sequence[str]` instead of `str`. For `src` layout, there would only be one `source-root`. This would neatly work for the above case. Let me know your thoughts. Sample project layout (borrowed from https://docs.pytest.org/en/7.1.x/explanation/goodpractices.html) ``` pyproject.toml src/ mypkg/ __init__.py app.py view.py tests/ test_app.py test_view.py ... ``` After the change, pylint command would be: ``` pylint --source-roots=src . ``` Note that this would be a general solution for a project with or without implicit namespace packages. ### Additional context _No response_