Raise helpful error message if montage is missing electrode positions

doc/changes/latest.rst

@@ -16,3 +16,5 @@
 
 Version 0.7
 ===========
+
+- Raise helpful error message when montage is incomplete (:pr:`181` by `Mathieu Scheltienne`_)

mne_icalabel/iclabel/_utils.py

@@ -53,9 +53,21 @@ def _cart2sph(_x, _y, _z):
         return azimuth, elevation, r
 
     # get the channel position dictionary
-    montage = raw.copy().pick_channels(picks, ordered=True).get_montage()
+    montage = raw.copy().pick(picks).get_montage()
+    if montage is None:
+        raise ValueError(
+            "Montage is not set. Please set the montage to provide the electrode "
+            "positions."
+        )
     positions = montage.get_positions()
     ch_pos = positions["ch_pos"]
+    # check that we do have a coordinate for every points
+    empty = [key for key in ch_pos if np.all(np.isnan(ch_pos[key]))]
+    if len(empty) != 0:
+        raise ValueError(
+            f"Channel position for {empty} is missing. Please check the montage set, "
+            "the channel names, and ensure that every channel has a position."
+        )
 
     # get locations as a 2D array
     locs = np.vstack(list(ch_pos.values()))

mne_icalabel/iclabel/tests/test_features.py

@@ -202,6 +202,21 @@ def test_eeg_topoplot(file, eeglab_result_file):
     assert np.allclose(topo, topo_eeglab, equal_nan=True)
 
 
+def test_eeg_topoplot_invalid_montage():
+    """Test that we raise an error if the montage is badly set."""
+    raw = read_raw(raw_eeglab_path, preload=True)
+    ica = read_ica_eeglab(raw_eeglab_path)
+    # get icawinv
+    icawinv, _ = _retrieve_eeglab_icawinv(ica)
+    # compute feature
+    raw.info["chs"][0]["loc"] = np.array([np.nan] * 12)
+    with pytest.raises(ValueError, match="Channel position for .* is missing"):
+        _eeg_topoplot(raw, icawinv, ica.ch_names)
+    raw.set_montage(None)
+    with pytest.raises(ValueError, match="Montage is not set"):
+        _eeg_topoplot(raw, icawinv, ica.ch_names)
+
+
 # ----------------------------------------------------------------------------
 @pytest.mark.filterwarnings("ignore:Estimated head radius.*:RuntimeWarning")
 @pytest.mark.parametrize(