Fix inferring fiducials from EEGLAB

doc/changes/devel.rst

@@ -83,6 +83,7 @@ Bugs
 - Fix bug with :func:`~mne.viz.plot_raw` where changing ``MNE_BROWSER_BACKEND`` via :func:`~mne.set_config` would have no effect within a Python session (:gh:`12078` by `Santeri Ruuskanen`_)
 - Improve handling of ``method`` argument in the channel interpolation function to support :class:`str` and raise helpful error messages (:gh:`12113` by `Mathieu Scheltienne`_)
 - Fix combination of ``DIN`` event channels into a single synthetic trigger channel ``STI 014`` by the MFF reader of :func:`mne.io.read_raw_egi` (:gh:`12122` by `Mathieu Scheltienne`_)
+- Fix bug with :func:`mne.io.read_raw_eeglab` and :func:`mne.read_epochs_eeglab` where automatic fiducial detection would fail for certain files (:gh:`12165` by `Clemens Brunner`_) 
 
 API changes
 ~~~~~~~~~~~

mne/io/eeglab/eeglab.py

@@ -165,17 +165,23 @@ def _get_montage_information(eeg, get_pos, *, montage_units):
         )
 
     lpa, rpa, nasion = None, None, None
-    if hasattr(eeg, "chaninfo") and len(eeg.chaninfo.get("nodatchans", [])):
-        for item in list(zip(*eeg.chaninfo["nodatchans"].values())):
-            d = dict(zip(eeg.chaninfo["nodatchans"].keys(), item))
-            if d.get("type", None) != "FID":
+    if hasattr(eeg, "chaninfo") and isinstance(eeg.chaninfo["nodatchans"], dict):
+        nodatchans = eeg.chaninfo["nodatchans"]
+        types = nodatchans.get("type", [])
+        descriptions = nodatchans.get("description", [])
+        xs = nodatchans.get("X", [])
+        ys = nodatchans.get("Y", [])
+        zs = nodatchans.get("Z", [])
+
+        for type_, description, x, y, z in zip(types, descriptions, xs, ys, zs):
+            if type_ != "FID":
                 continue
-            elif d.get("description", None) == "Nasion":
-                nasion = np.array([d["X"], d["Y"], d["Z"]])
-            elif d.get("description", None) == "Right periauricular point":
-                rpa = np.array([d["X"], d["Y"], d["Z"]])
-            elif d.get("description", None) == "Left periauricular point":
-                lpa = np.array([d["X"], d["Y"], d["Z"]])
+            if description == "Nasion":
+                nasion = np.array([x, y, z])
+            elif description == "Right periauricular point":
+                rpa = np.array([x, y, z])
+            elif description == "Left periauricular point":
+                lpa = np.array([x, y, z])
 
     # Always check this even if it's not used
     _check_option("montage_units", montage_units, ("m", "dm", "cm", "mm", "auto"))