Use self.name to construct the result of DatetimeIndex.snap, fix pandas-dev#25575.

Signed-off-by: HE, Tao <[email protected]>

Author: sighingnow

doc/source/whatsnew/v0.24.2.rst

@@ -31,6 +31,7 @@ Fixed Regressions
 - Fixed regression in ``IntervalDtype`` construction where passing an incorrect string with 'Interval' as a prefix could result in a ``RecursionError``. (:issue:`25338`)
 - Fixed regression in :class:`Categorical`, where constructing it from a categorical ``Series`` and an explicit ``categories=`` that differed from that in the ``Series`` created an invalid object which could trigger segfaults. (:issue:`25318`)
 - Fixed pip installing from source into an environment without NumPy (:issue:`25193`)
+- Fixed name preserving bug of :meth:`DatetimeIndex.snap` (:issue:`25575`)
 
 .. _whatsnew_0242.enhancements:
 

pandas/core/indexes/datetimes.py

@@ -787,8 +787,7 @@ def snap(self, freq='S'):
             snapped[i] = s
 
         # we know it conforms; skip check
-        return DatetimeIndex._simple_new(snapped, freq=freq)
-        # TODO: what about self.name?  tz? if so, use shallow_copy?
+        return DatetimeIndex._simple_new(snapped, name=self.name, freq=freq)
 
     def join(self, other, how='left', level=None, return_indexers=False,
              sort=False):

pandas/tests/series/indexing/test_datetime.py

@@ -54,12 +54,14 @@ def test_fancy_setitem():
 
 def test_dti_snap():
     dti = DatetimeIndex(['1/1/2002', '1/2/2002', '1/3/2002', '1/4/2002',
-                         '1/5/2002', '1/6/2002', '1/7/2002'], freq='D')
+                         '1/5/2002', '1/6/2002', '1/7/2002'],
+                        name='my_dti', freq='D')
 
     res = dti.snap(freq='W-MON')
-    exp = date_range('12/31/2001', '1/7/2002', freq='w-mon')
+    exp = date_range('12/31/2001', '1/7/2002', name='my_dti', freq='w-mon')
     exp = exp.repeat([3, 4])
     assert (res == exp).all()
+    assert res.name == exp.name
 
     res = dti.snap(freq='B')