scope not assigned when loading a derivative directory directly

[eric-d-knowles]

When loading a BIDS derivative directory directly using BIDSLayout, files are not assigned a .scope attribute, even though a valid dataset_description.json with a "Name" field is present and correctly parsed.

This behavior prevents scope-based filtering (e.g., scope='cleaned') from working when derivative layouts are loaded independently or added via add_derivatives().

Given this structure:

/path/to/dataset/
├── dataset_description.json
└── derivatives/
    └── cleaned/
        ├── dataset_description.json  # "Name": "cleaned"
        └── sub-001/
            └── func/
                ├── sub-001_task-test_run-1_desc-cleaned_bold.nii.gz
                └── sub-001_task-test_run-1_desc-resampled_bold.nii.gz

dataset_description.json:

{
"Name": "cleaned",
"BIDSVersion": "1.6.0",
"DatasetType": "derivative"
}

Python code:

from bids import BIDSLayout

layout = BIDSLayout('/path/to/dataset/derivatives/cleaned', validate=False, derivatives=False)
files = layout.get(suffix='bold', extension='nii.gz', return_type='obj')

print(files[0].path)
print("scope:", getattr(files[0], 'scope', 'NO_SCOPE'))

Expected behavior:

scope: cleaned

Actual behavior:

scope: NO_SCOPE

Environment:

PyBIDS version: 0.19.0
Python version: 3.11.11
Platform: Linux