Fix eeg rereferencing error when ch_type is defined (mne-tools#7847)

* Fix eeg rereferencing error when ch_type is defined

When calling raw.set_eeg_reference with a pre-defined channel type, the error "local variable 'type_' referenced before assignment" occurs.
eg. raw.set_eeg_reference(ref_channels='average', projection=False, ch_type='seeg')

type_ is set while detecting the channel type that should be referenced. This commit uses the ch_type variable instead of type_, which is guaranteed to be set.

* TST: Add test

Co-authored-by: Eric Larson <[email protected]>

doc/changes/latest.inc

@@ -216,6 +216,8 @@ Bug
 
 - Fix bug with `mne.SourceSpaces.export_volume` with ``use_lut=False`` where no values were written by `Eric Larson`_
 
+- Fix bug with logging in :meth:`mne.io.Raw.set_eeg_reference` and related functions by `Simeon Wong`_
+
 - Fix bug with :func:`mne.preprocessing.annotate_movement` where bad data segments, specified in ``raw.annotations``, would be handled incorrectly by `Luke Bloy`_
 
 - Fix bug with :func:`mne.compute_source_morph` when more than one volume source space was present (e.g., when using labels) where only the first label would be interpolated when ``mri_resolution=True`` by `Eric Larson`_

doc/changes/names.inc

@@ -298,6 +298,8 @@
 
 .. _Adam Li: http://github.com/adam2392
 
+.. _Simeon Wong: https://github.com/dtxe
+
 .. _Ramiro Gatti: https://github.com/ragatti
 
 .. _Liberty Hamilton: https://github.com/libertyh

mne/io/tests/test_reference.py

@@ -22,7 +22,7 @@
 from mne.io.proj import _has_eeg_average_ref_proj, Projection
 from mne.io.reference import _apply_reference
 from mne.datasets import testing
-from mne.utils import run_tests_if_main
+from mne.utils import run_tests_if_main, catch_logging
 
 data_dir = op.join(testing.data_path(download=False), 'MEG', 'sample')
 fif_fname = op.join(data_dir, 'sample_audvis_trunc_raw.fif')
@@ -232,13 +232,22 @@ def test_set_eeg_reference():
     with pytest.raises(ValueError, match='supported for ref_channels="averag'):
         set_eeg_reference(raw, ['EEG 001'], True, True)
 
+
+@pytest.mark.parametrize('ch_type', ('auto', 'ecog'))
+def test_set_eeg_reference_ch_type(ch_type):
+    """Test setting EEG reference for ECoG."""
     # gh-6454
     rng = np.random.RandomState(0)
     data = rng.randn(3, 1000)
     raw = RawArray(data, create_info(3, 1000., ['ecog'] * 2 + ['misc']))
-    reref, ref_data = set_eeg_reference(raw.copy())
+    with catch_logging() as log:
+        reref, ref_data = set_eeg_reference(raw.copy(), ch_type=ch_type,
+                                            verbose=True)
+    assert 'Applying a custom ECoG' in log.getvalue()
     assert reref.info['custom_ref_applied']  # gh-7350
     _test_reference(raw, reref, ref_data, ['0', '1'])
+    with pytest.raises(ValueError, match='No channels supplied'):
+        set_eeg_reference(raw, ch_type='eeg')
 
 
 def test_set_eeg_reference_rest():