FIX: make sure Dataframes with a DatetimeIndex come out as str labels as before (fixes larray-project#1187)

In fact, this is about reintroducing a bug I fixed by accident to avoid breaking users existing code in a bugfix release

Author: gdementen

larray/inout/pandas.py

@@ -59,6 +59,10 @@ def simple_index_to_labels(idx: pd.Index, sort=True, keep_object=True) -> np.nda
             labels = idx.to_numpy()
         else:
             labels = np.asarray(idx.to_list())
+    # this is a bug introduced on purpose to keep backward compatibility
+    # (see issue #1187)
+    if isinstance(idx, pd.DatetimeIndex):
+        labels = labels.astype(str)
     return labels
 
 

larray/tests/test_array.py

@@ -4134,6 +4134,8 @@ def test_read_excel_pandas():
 
 
 def test_from_lists():
+    from datetime import datetime
+
     expected = ndtest((2, 2, 3))
 
     # simple
@@ -4200,6 +4202,15 @@ def test_from_lists():
                              ['c1', 'FO', 0, 0, 2]], sort_columns=True)
     assert_larray_equal(sorted_arr, expected)
 
+    # with datetime labels
+    res = from_lists([['str', 'date', 'value'],
+                      ['abc', datetime.now(), 1]],
+                     nb_axes=3)
+    # this is what we SHOULD return but we do not so far to avoid breaking
+    # backward compatibility (see issue #1187)
+    # assert res.axes[1].dtype == 'datetime64[ns]'
+    assert res.axes[1].dtype == '<U48'
+
 
 def test_to_series():
     # simple test