Make set_eeg_reference working with a string for a channel name

Author: mistraube

mne/_fiff/reference.py

@@ -414,6 +414,10 @@ def set_eeg_reference(
         logger.info("Applying a custom dict-based reference.")
         return _apply_dict_reference(inst, ref_channels)
 
+    # We need 'ref_channels' to be a list, even for a single channel name.
+    if isinstance(ref_channels, str) and ref_channels not in ("average", "REST"):
+        ref_channels = [ref_channels]
+
     ch_type = _get_ch_type(inst, ch_type)
 
     if projection:  # average reference projector

mne/_fiff/tests/test_reference.py

@@ -257,6 +257,10 @@ def test_set_eeg_reference():
     with pytest.raises(ValueError, match='supported for ref_channels="averag'):
         set_eeg_reference(raw, ["EEG 001"], True, True)
 
+    # Test passing a single channel name as string
+    reref, ref_data = set_eeg_reference(raw, "EEG 001", copy=True)
+    _test_reference(raw, reref, ref_data, ["EEG 001"])
+
 
 @pytest.mark.parametrize(
     "ch_type, msg",