Port fix from pandas-dev/pandas#55283 to cftime resample (#8393)

* Port fix from pandas-dev/pandas#55283 to cftime resample [test-upstream]

* Skip test for pandas versions older than 2.2 [test-upstream]

* Update doc/whats-new.rst

Co-authored-by: Justus Magin <[email protected]>

---------

Co-authored-by: Deepak Cherian <[email protected]>
Co-authored-by: Justus Magin <[email protected]>

Author: 3 people

doc/whats-new.rst

@@ -43,6 +43,13 @@ Deprecations
 Bug fixes
 ~~~~~~~~~
 
+- Port `bug fix from pandas <https://github.com/pandas-dev/pandas/pull/55283>`_
+  to eliminate the adjustment of resample bin edges in the case that the
+  resampling frequency has units of days and is greater than one day
+  (e.g. ``"2D"``, ``"3D"`` etc.) and the ``closed`` argument is set to
+  ``"right"`` to xarray's implementation of resample for data indexed by a
+  :py:class:`CFTimeIndex` (:pull:`8393`).
+  By `Spencer Clark <https://github.com/spencerkclark>`_.
 
 Documentation
 ~~~~~~~~~~~~~

xarray/core/resample_cftime.py

@@ -45,7 +45,6 @@
 
 from xarray.coding.cftime_offsets import (
     BaseCFTimeOffset,
-    Day,
     MonthEnd,
     QuarterEnd,
     Tick,
@@ -254,8 +253,7 @@ def _adjust_bin_edges(
     labels: np.ndarray,
 ):
     """This is required for determining the bin edges resampling with
-    daily frequencies greater than one day, month end, and year end
-    frequencies.
+    month end, quarter end, and year end frequencies.
 
     Consider the following example.  Let's say you want to downsample the
     time series with the following coordinates to month end frequency:
@@ -283,14 +281,8 @@ def _adjust_bin_edges(
     The labels are still:
 
     CFTimeIndex([2000-01-31 00:00:00, 2000-02-29 00:00:00], dtype='object')
-
-    This is also required for daily frequencies longer than one day and
-    year-end frequencies.
     """
-    is_super_daily = isinstance(freq, (MonthEnd, QuarterEnd, YearEnd)) or (
-        isinstance(freq, Day) and freq.n > 1
-    )
-    if is_super_daily:
+    if isinstance(freq, (MonthEnd, QuarterEnd, YearEnd)):
         if closed == "right":
             datetime_bins = datetime_bins + datetime.timedelta(days=1, microseconds=-1)
         if datetime_bins[-2] > index.max():

xarray/tests/test_cftimeindex_resample.py

@@ -6,6 +6,7 @@
 import numpy as np
 import pandas as pd
 import pytest
+from packaging.version import Version
 
 import xarray as xr
 from xarray.core.pdcompat import _convert_base_to_offset
@@ -122,6 +123,16 @@ def da(index) -> xr.DataArray:
 )
 def test_resample(freqs, closed, label, base, offset) -> None:
     initial_freq, resample_freq = freqs
+    if (
+        resample_freq == "4001D"
+        and closed == "right"
+        and Version(pd.__version__) < Version("2.2")
+    ):
+        pytest.skip(
+            "Pandas fixed a bug in this test case in version 2.2, which we "
+            "ported to xarray, so this test no longer produces the same "
+            "result as pandas for earlier pandas versions."
+        )
     start = "2000-01-01T12:07:01"
     loffset = "12H"
     origin = "start"