skip t1w file existence check if anat_derivatives are provided

Author: bpinsard

niworkflows/interfaces/bids.py

@@ -222,17 +222,20 @@ class BIDSDataGrabber(SimpleInterface):
 
     def __init__(self, *args, **kwargs):
         anat_only = kwargs.pop("anat_only")
+        anat_derivatives = kwargs.pop("anat_derivatives")
         super(BIDSDataGrabber, self).__init__(*args, **kwargs)
         if anat_only is not None:
             self._require_funcs = not anat_only
+        if anat_derivatives is not None:
+            self._require_t1w = not anat_derivatives
 
     def _run_interface(self, runtime):
         bids_dict = self.inputs.subject_data
 
         self._results["out_dict"] = bids_dict
         self._results.update(bids_dict)
 
-        if not bids_dict["t1w"]:
+        if self._require_t1w and not bids_dict['t1w']:
             raise FileNotFoundError(
                 "No T1w images found for subject sub-{}".format(self.inputs.subject_id)
             )