FIX: Handle empty landmarkLabels in read_raw_snirf

doc/changes/dev/13628.bugfix.rst

@@ -0,0 +1 @@
+Fix :func:`mne.io.read_raw_snirf` raising ``TypeError`` when ``landmarkLabels`` is empty or scalar, by `Bruno Aristimunha`_.

mne/io/snirf/_snirf.py

@@ -388,6 +388,11 @@ def natural_keys(text):
                 diglocs = np.array(dat.get("/nirs/probe/landmarkPos3D"))
                 diglocs /= length_scaling
                 digname = np.array(dat.get("/nirs/probe/landmarkLabels"))
+                # Handle empty or scalar landmarkLabels (see gh-13627)
+                if digname.ndim == 0 or digname.size == 0:
+                    digname = []
+                else:
+                    digname = _correct_shape(digname)
                 nasion, lpa, rpa, hpi = None, None, None, None
                 extra_ps = dict()
                 for idx, dign in enumerate(digname):

mne/io/snirf/tests/test_snirf.py

@@ -284,6 +284,33 @@ def test_snirf_nonstandard(tmp_path):
         f.create_dataset("nirs/metaDataTags/MNE_coordFrame", data=[1])
 
 
+@requires_testing_data
+def test_snirf_empty_landmark_labels(tmp_path):
+    """Test reading SNIRF files with empty landmarkLabels (gh-13627)."""
+    shutil.copy(sfnirs_homer_103_wShort, tmp_path / "empty_labels.snirf")
+    fname = tmp_path / "empty_labels.snirf"
+
+    # Modify file to have landmarkPos3D but empty/scalar landmarkLabels
+    with h5py.File(fname, "r+") as f:
+        # Remove existing landmark data if present
+        if "landmarkPos3D" in f["nirs/probe"]:
+            del f["nirs/probe/landmarkPos3D"]
+        if "landmarkLabels" in f["nirs/probe"]:
+            del f["nirs/probe/landmarkLabels"]
+
+        # Add non-empty landmarkPos3D
+        f.create_dataset(
+            "nirs/probe/landmarkPos3D",
+            data=np.array([[0.0, 0.0, 0.0], [1.0, 0.0, 0.0]]),
+        )
+        # Add empty scalar landmarkLabels (this triggers the bug in gh-13627)
+        f.create_dataset("nirs/probe/landmarkLabels", data=b"")
+
+    # This should not raise "TypeError: iteration over a 0-d array"
+    raw = read_raw_snirf(fname, preload=True)
+    assert raw.info["dig"] is not None
+
+
 @requires_testing_data
 def test_snirf_nirsport2():
     """Test reading SNIRF files."""