fix: allow new fields to be registered

Author: satra

nipype/interfaces/io.py

@@ -129,12 +129,14 @@ class DataSinkInputSpec(DynamicTraitedSpec, BaseInterfaceInputSpec):
                                   desc='remove dest directory when copying dirs')
 
     def __setattr__(self, key, value):
-        super(DataSinkInputSpec, self).__setattr__(key, value)
         if key not in self.copyable_trait_names():
+            if not isdefined(value):
+                super(DataSinkInputSpec, self).__setattr__(key, value)
             self._outputs[key] = value
         else:
             if key in self._outputs:
                 self._outputs[key] = value
+            super(DataSinkInputSpec, self).__setattr__(key, value)
 
 class DataSink(IOBase):
     """ Generic datasink module to store structured outputs

nipype/interfaces/tests/test_io.py

@@ -23,6 +23,8 @@ def test_datasink():
     yield assert_equal, ds.inputs._outputs, {}
     ds = nio.DataSink(base_directory = 'foo')
     yield assert_equal, ds.inputs.base_directory, 'foo'
+    ds = nio.DataSink(infields=['test'])
+    yield assert_true, 'test' in ds.inputs.copyable_trait_names()
 
 def test_datasink_substitutions():
     indir = mkdtemp(prefix='-Tmp-nipype_ds_subs_in')