[pybids-core] Loading BIDSLayout with a path to a derivative folder

[erdalkaraca]

In one of the unit tests, a BIDSLayout is created using a derivative path:

    def test_dataset_missing_generatedby_fails_validation(self):
        dataset_path = Path("ds005_derivs", "format_errs", "no_pipeline_description")
        with pytest.raises(BIDSDerivativesValidationError):
            BIDSLayout(Path(get_test_data_path())/dataset_path)

The expectation is to raise a validation error as the derivative has no GeneratedBy field in its dataset_description file.
How can the implementation be sure that the provided path is a derivative and not the root folder of a dataset?

I am not sure if it is safe to also interpret the path's upper hierarchy. Is this a functionality that you (pybids user community) are expecting and depend on?

[tsalo]

Sorry for the massive delay. Any BIDS derivatives dataset should have "DatasetType": "derivatives" in the dataset_description.json, so I would assume that pybids is checking that.