FIX: Handle an Eyelink File with blank lines injected throughout file (mne-tools#13469)

Author: scott-huberty

doc/changes/dev/13469.bugfix.rst

@@ -0,0 +1 @@
+Make :func:`mne.preprocessing.eyetracking.read_eyelink_calibration` robust to files with blank lines, by `Scott Huberty`_.

mne/io/eyelink/_utils.py

@@ -992,17 +992,24 @@ def _parse_calibration(
 
             n_points = int(regex.search(model).group())  # e.g. 13
             n_points *= 2 if "LR" in line else 1  # one point per eye if "LR"
+
             # The next n_point lines contain the validation data
             points = []
-            for validation_index in range(n_points):
-                subline = lines[line_number + validation_index + 1]
-                if "!CAL VALIDATION" in subline:
+            line_idx = line_number + 1
+            read_points = 0
+            while read_points < n_points and line_idx < len(lines):
+                subline = lines[line_idx].strip()
+                line_idx += 1
+
+                if not subline or "!CAL VALIDATION" in subline:
                     continue  # for bino mode, skip the second eye's validation summary
+
                 subline_eye = subline.split("at")[0].split()[-1].lower()  # e.g. 'left'
                 if subline_eye != this_eye:
                     continue  # skip the validation lines for the other eye
                 point_info = _parse_validation_line(subline)
                 points.append(point_info)
+                read_points += 1
             # Convert the list of validation data into a numpy array
             positions = np.array([point[:2] for point in points])
             offsets = np.array([point[2] for point in points])

mne/preprocessing/eyetracking/tests/test_calibration.py

@@ -2,6 +2,8 @@
 # License: BSD-3-Clause
 # Copyright the MNE-Python contributors.
 
+from pathlib import Path
+
 import numpy as np
 import pytest
 
@@ -251,3 +253,35 @@ def test_plot_calibration(fname, axes):
         scatter2.get_offsets(), np.column_stack((gaze_x, gaze_y))
     )
     plt.close(fig)
+
+
+@requires_testing_data
+@pytest.mark.parametrize("fname", [(fname)])
+def test_calibration_newlines(fname, tmp_path):
+    """Test reading a calibration with blank lines between each data line."""
+    # Calibration reading should be robust to what we are about to do to this file
+    want_cals = read_eyelink_calibration(fname)
+
+    # Let's interleave blank lines into this file
+    lines = Path(fname).read_text().splitlines()
+    cal_start = lines.index(">>>>>>> CALIBRATION (HV13,P-CR) FOR LEFT: <<<<<<<<<")
+    cal_end = lines.index("INPUT\t5509657\t0")
+    cal_block = lines[cal_start : cal_end + 1]
+
+    # Inject empty strings between each line in the calibration block
+    interleaved = [elem for line in cal_block for elem in (line, "")]
+
+    # Replace the original calibration block with the interleaved one
+    new_lines = lines[:cal_start] + interleaved + lines[cal_end + 1 :]
+
+    out_fname = tmp_path / "weird_calibration.asc"
+    out_fname.write_text("\n".join(new_lines))
+    cals = read_eyelink_calibration(out_fname)
+
+    # The added blank lines should not affect the values that we read in...
+    assert len(cals) == len(want_cals)
+    assert cals[1]["eye"] == want_cals[1]["eye"]
+    np.testing.assert_allclose(cals[0]["onset"], want_cals[0]["onset"])
+    np.testing.assert_allclose(cals[0]["positions"], want_cals[0]["positions"])
+    np.testing.assert_allclose(cals[1]["offsets"], want_cals[1]["offsets"])
+    np.testing.assert_allclose(cals[0]["gaze"], want_cals[0]["gaze"])