Birthday input cast to datetime.date

doc/changes/devel/13284.bugfix.rst

@@ -0,0 +1 @@
+Fixed bug where saving FIFF files failed when ``info["subject_info"]["birthday"]`` was a :class:`pandas.Timestamp` instead of :class:`datetime.date`, by :newcontrib:`Laurent Le Mentec`.

mne/_fiff/meas_info.py

@@ -1011,6 +1011,19 @@ def _check_types(x, *, info, name, types, cast=None):
     return x
 
 
+def _check_bday(birthday_input, *, info):
+    date = _check_types(
+        birthday_input,
+        info=info,
+        name='subject_info["birthday"]',
+        types=(datetime.date, None),
+    )
+    # test if we have a pd.Timestamp
+    if hasattr(date, "date"):
+        date = date.date()
+    return date
+
+
 class SubjectInfo(ValidatedDict):
     _attributes = {
         "id": partial(_check_types, name='subject_info["id"]', types=int),
@@ -1022,9 +1035,7 @@ class SubjectInfo(ValidatedDict):
         "middle_name": partial(
             _check_types, name='subject_info["middle_name"]', types=str
         ),
-        "birthday": partial(
-            _check_types, name='subject_info["birthday"]', types=(datetime.date, None)
-        ),
+        "birthday": partial(_check_bday),
         "sex": partial(_check_types, name='subject_info["sex"]', types=int),
         "hand": partial(_check_types, name='subject_info["hand"]', types=int),
         "weight": partial(

mne/_fiff/tests/test_meas_info.py

@@ -773,6 +773,27 @@ def test_meas_date_convert(stamp, dt):
     assert str(dt[0]) in repr(info)
 
 
+def test_birthday_input():
+    """Test that birthday input is handled correctly."""
+    pd = pytest.importorskip("pandas")
+
+    # Test valid date
+    info = create_info(ch_names=["EEG 001"], sfreq=1000.0, ch_types="eeg")
+    info["subject_info"] = {}
+    info["subject_info"]["birthday"] = date(2000, 1, 1)
+    assert info["subject_info"]["birthday"] == date(2000, 1, 1)
+
+    # pandas Timestamp should convert to datetime date
+    info["subject_info"]["birthday"] = pd.Timestamp("2000-01-01")
+    assert info["subject_info"]["birthday"] == date(2000, 1, 1)
+    # Ensure we've converted it during setting
+    assert not isinstance(info["subject_info"]["birthday"], pd.Timestamp)
+
+    # Test invalid date raises error
+    with pytest.raises(TypeError, match="must be an instance of date"):
+        info["subject_info"]["birthday"] = "not a date"
+
+
 def _complete_info(info):
     """Complete the meas info fields."""
     for key in ("file_id", "meas_id"):