MRG: Correctly handle reading when BIDS channel order differs from Raw

doc/whats_new.rst

@@ -21,6 +21,7 @@ The following authors contributed for the first time. Thank you so much! 🤩
 
 The following authors had contributed before. Thank you for sticking around! 🤘
 
+* `Richard Höchenberger`_
 * `Stefan Appelhoff`_
 
 Detailed list of changes
@@ -44,7 +45,7 @@ Detailed list of changes
 🪲 Bug fixes
 ^^^^^^^^^^^^
 
-- nothing yet
+- Fix reading when the channel order differs between ``*_channels.tsv`` and the raw data file, which would previously throw an error, by `Richard Höchenberger`_ (:gh:`1171`)
 
 :doc:`Find out what was new in previous releases <whats_new_previous_releases>`
 

mne_bids/read.py

@@ -642,9 +642,7 @@ def _handle_channels_reading(channels_fname, raw):
             f"set channel names."
         )
     else:
-        for bids_ch_name, raw_ch_name in zip(ch_names_tsv, raw.ch_names.copy()):
-            if bids_ch_name != raw_ch_name:
-                raw.rename_channels({raw_ch_name: bids_ch_name})
+        raw.rename_channels(dict(zip(raw.ch_names, ch_names_tsv)))
 
     # Set the channel types in the raw data according to channels.tsv
     channel_type_bids_mne_map_available_channels = {

mne_bids/tests/test_read.py

@@ -1258,7 +1258,7 @@ def test_ignore_exclude_param(tmp_path):
 @pytest.mark.filterwarnings(warning_str["channel_unit_changed"])
 @testing.requires_testing_data
 def test_channels_tsv_raw_mismatch(tmp_path):
-    """Test behavior when channels.tsv contains channels not found in raw."""
+    """Test mismatch between channels in channels.tsv and raw."""
     bids_path = _bids_path.copy().update(root=tmp_path, datatype="meg", task="rest")
 
     # Remove one channel from the raw data without updating channels.tsv
@@ -1311,6 +1311,19 @@ def test_channels_tsv_raw_mismatch(tmp_path):
     ):
         read_raw_bids(bids_path)
 
+    # Test mismatched channel ordering between channels.tsv and raw
+    raw = _read_raw_fif(raw_fname, verbose=False)
+    write_raw_bids(raw, bids_path=bids_path, overwrite=True, verbose=False)
+
+    ch_names_orig = raw.ch_names.copy()
+    ch_names_new = ch_names_orig.copy()
+    ch_names_new[1], ch_names_new[0] = ch_names_new[0], ch_names_new[1]
+    raw.reorder_channels(ch_names_new)
+    raw.save(raw_path, overwrite=True)
+
+    raw = read_raw_bids(bids_path)
+    assert raw.ch_names == ch_names_orig
+
 
 @testing.requires_testing_data
 def test_file_not_found(tmp_path):