From 098daf3020e817d03a17a81963ad3cf831fbb48c Mon Sep 17 00:00:00 2001
From: keisukefujii <fujiisoup@gmail.com>
Date: Mon, 6 May 2019 23:20:12 +0200
Subject: [PATCH 1/2] Fix: 2940

---
 doc/whats-new.rst      | 11 +++++++----
 xarray/core/rolling.py |  4 ++--
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/doc/whats-new.rst b/doc/whats-new.rst
index b88d10ffc23..d7ce50ecc00 100644
--- a/doc/whats-new.rst
+++ b/doc/whats-new.rst
@@ -27,10 +27,13 @@ Enhancements
 - Character arrays' character dimension name decoding and encoding handled by
   ``var.encoding['char_dim_name']`` (:issue:`2895`)
   By `James McCreight <https://github.com/jmccreight>`_.
-   
+
 Bug fixes
 ~~~~~~~~~
 
+- a bug fix in rolling with dask and bottleneck
+  (:issue:`2940`)
+  By `Keisuke Fujii <https://github.com/fujiisoup>`_.
 - indexing with an empty list creates an object with zero-length axis (:issue:`2882`)
   By `Mayeul d'Avezac <https://github.com/mdavezac>`_.
 - Return correct count for scalar datetime64 arrays (:issue:`2770`)
@@ -147,9 +150,9 @@ Other enhancements
   By `Keisuke Fujii <https://github.com/fujiisoup>`_.
 - Added :py:meth:`~xarray.Dataset.drop_dims` (:issue:`1949`).
   By `Kevin Squire <https://github.com/kmsquire>`_.
-- ``xr.open_zarr`` now accepts manually specified chunks with the ``chunks=`` 
-  parameter. ``auto_chunk=True`` is equivalent to ``chunks='auto'`` for 
-  backwards compatibility. The ``overwrite_encoded_chunks`` parameter is 
+- ``xr.open_zarr`` now accepts manually specified chunks with the ``chunks=``
+  parameter. ``auto_chunk=True`` is equivalent to ``chunks='auto'`` for
+  backwards compatibility. The ``overwrite_encoded_chunks`` parameter is
   added to remove the original zarr chunk encoding.
   By `Lily Wang <https://github.com/lilyminium>`_.
 
diff --git a/xarray/core/rolling.py b/xarray/core/rolling.py
index 8a974e2da72..94369bea906 100644
--- a/xarray/core/rolling.py
+++ b/xarray/core/rolling.py
@@ -275,7 +275,7 @@ def wrapped_func(self, **kwargs):
                 if isinstance(padded.data, dask_array_type):
                     # Workaround to make the padded chunk size is larger than
                     # self.window-1
-                    shift = - (self.window + 1) // 2
+                    shift = - (self.window - 1)
                     offset = (self.window - 1) // 2
                     valid = (slice(None), ) * axis + (
                         slice(offset, offset + self.obj.shape[axis]), )
@@ -285,7 +285,7 @@ def wrapped_func(self, **kwargs):
                 padded = padded.pad_with_fill_value({self.dim: (0, -shift)})
 
             if isinstance(padded.data, dask_array_type):
-                values = dask_rolling_wrapper(func, padded,
+                values = dask_rolling_wrapper(func, padded.data,
                                               window=self.window,
                                               min_count=min_count,
                                               axis=axis)

From ca96cc3b709ef043a7fa54030c6ddf26da8b4089 Mon Sep 17 00:00:00 2001
From: keisukefujii <fujiisoup@gmail.com>
Date: Mon, 6 May 2019 23:38:41 +0200
Subject: [PATCH 2/2] Remove skipping test for this bug.

---
 xarray/tests/test_dataarray.py | 1 -
 1 file changed, 1 deletion(-)

diff --git a/xarray/tests/test_dataarray.py b/xarray/tests/test_dataarray.py
index ab6a5eb3626..65ee0c0d69e 100644
--- a/xarray/tests/test_dataarray.py
+++ b/xarray/tests/test_dataarray.py
@@ -3618,7 +3618,6 @@ def test_rolling_wrapped_bottleneck(da, name, center, min_periods):
 @pytest.mark.parametrize('center', (True, False, None))
 @pytest.mark.parametrize('min_periods', (1, None))
 @pytest.mark.parametrize('window', (7, 8))
-@pytest.mark.xfail(reason='https://github.com/pydata/xarray/issues/2940')
 def test_rolling_wrapped_dask(da_dask, name, center, min_periods, window):
     pytest.importorskip('dask.array')
     # dask version