FIX: handle empty first Eyelink recording block

Author: varunkasyap

doc/changes/dev/13555.bugfix.rst

@@ -0,0 +1 @@
+Fix bug where :func:`mne.io.read_raw_eyelink` raised an error when reading Eyelink files with an empty first recording block, by :newcontrib:`Varun Kasyap` (:gh:`13555`).

doc/changes/names.inc

@@ -336,6 +336,7 @@
 .. _Tziona NessAiver: https://github.com/TzionaN
 .. _user27182: https://github.com/user27182
 .. _Valerii Chirkov: https://github.com/vagechirkov
+.. _Varun Kasyap Pentamaraju: https://github.com/varunkasyap
 .. _Velu Prabhakar Kumaravel: https://github.com/vpKumaravel
 .. _Victor Ferat: https://github.com/vferat
 .. _Victoria Peterson: https://github.com/vpeterson

mne/io/eyelink/_utils.py

@@ -90,7 +90,14 @@ def _parse_eyelink_ascii(
                 raw_extras["dfs"][key], max_time=overlap_threshold
             )
     # ======================== Info for BaseRaw ========================
-    eye_ch_data = raw_extras["dfs"]["samples"][ch_names].to_numpy().T
+    dfs = raw_extras["dfs"]
+
+    if "samples" not in dfs or dfs["samples"].empty:
+        logger.info("No sample data found, creating empty Raw object.")
+        eye_ch_data = np.empty((len(ch_names), 0))
+    else:
+        eye_ch_data = dfs["samples"][ch_names].to_numpy().T
+
     info = _create_info(ch_names, raw_extras)
 
     return eye_ch_data, info, raw_extras

mne/io/eyelink/eyelink.py

@@ -123,7 +123,9 @@ def __init__(
             eye_annots = _make_eyelink_annots(
                 self._raw_extras[0]["dfs"], create_annotations, apply_offsets
             )
-        if gap_annots and eye_annots:  # set both
+        if self.n_times == 0:
+            logger.info("No samples found in recording, skipping annotation creation.")
+        elif gap_annots and eye_annots:  # set both
             self.set_annotations(gap_annots + eye_annots)
         elif gap_annots:
             self.set_annotations(gap_annots)

mne/io/eyelink/tests/test_eyelink.py

@@ -523,3 +523,24 @@ def test_href_eye_events(tmp_path):
     # Just check that we actually parsed the Saccade and Fixation events
     assert "saccade" in raw.annotations.description
     assert "fixation" in raw.annotations.description
+
+
+@requires_testing_data
+def test_empty_first_trial(tmp_path):
+    """Test reading a file with an empty first trial."""
+    out_file = tmp_path / "tmp_eyelink.asc"
+    # Use a real eyelink file as base
+    lines = fname.read_text("utf-8").splitlines()
+    # Find first START and END
+    end_idx = next(i for i, line in enumerate(lines) if line.startswith("END"))
+    # Keep headers + START..END but REMOVE all numeric sample lines
+    first_block = []
+    for line in lines[: end_idx + 1]:
+        tokens = line.split()
+        if line.startswith("START") or not tokens or not tokens[0].isdigit():
+            first_block.append(line)
+
+    # Append rest of file (second trial onwards)
+    rest = lines[end_idx + 1 :]
+    out_file.write_text("\n".join(first_block + rest), encoding="utf-8")
+    read_raw_eyelink(out_file)