issues

I think we should issue a patch release soon.

• [x] xarray.map_blocks will break with new dask,distributed releases this week since we don't have a released version with https://github.com/pydata/xarray/pull/5271
• [x] #5296: fix for regression reported in #5295
• [x] #5300: fix the error message in #5291 so that it is more helpful. It's a key entry point for new users.
• [x] #5299 RTD build is broken
• [ ] #5329 should throw FileNotFoundError error on nonexistent file?

Nice to have - [ ] #5252 zarr region - [ ] #5045 assigning to subset - [x] #5239 drop_duplicates - [x] #5288 invalid reference date error

Thoughts? Volunteers?

• [x] Closes #3470
• [x] Tests added
• [x] Passes isort -rc . && black . && mypy . && flake8
• [x] Fully documented, including whats-new.rst for all changes and api.rst for new API

It'd be nice to issue a release by the end of March (two months since previous release)

Please edit this list as you wish.

Must-have - [x] #3862 error when assigning to IndexVariable.values - [x] #3840 delete index when deleting coordinate variable - [x] #3874 un-xfail the tests from #3808 (https://github.com/pydata/xarray/issues/3751#issuecomment-599231986) - [x] #3833, #3870 HTML repr with non-str keys fix (since it is now on by default)

Nice to have - [ ] #3816 map_blocks template - [x] #3817 map_blocks new unindexed dimension - [ ] #3818 map_blocks dask args - [ ] #3847 assert_allclose diff - [x] #3826 ellipsis in stack - [x] #3836 where docstring - [ ] some progress on #3868 - [ ] #3594 unit support - [ ] #3871 idxmin, idxmax

https://dev.azure.com/xarray/xarray/_build/results?buildId=1101&view=logs

``` =================================== FAILURES =================================== ____ testdatetime_reduce[False] ______

dask = False

@arm_xfail
@pytest.mark.parametrize("dask", [False, True])
def test_datetime_reduce(dask):
    time = np.array(pd.date_range("15/12/1999", periods=11))
    time[8:11] = np.nan
    da = DataArray(np.linspace(0, 365, num=11), dims="time", coords={"time": time})

    if dask and has_dask:
        chunks = {"time": 5}
        da = da.chunk(chunks)

    actual = da["time"].mean()

  assert not pd.isnull(actual)

E AssertionError: assert not True E + where True = <function isna at 0x7f2475449ae8>(<xarray.DataArray 'time' ()>\narray('NaT', dtype='datetime64[ns]')) E + where <function isna at 0x7f2475449ae8> = pd.isnull

xarray/tests/test_duck_array_ops.py:288: AssertionError ____ test_datetime_reduce[True] ______

dask = True

@arm_xfail
@pytest.mark.parametrize("dask", [False, True])
def test_datetime_reduce(dask):
    time = np.array(pd.date_range("15/12/1999", periods=11))
    time[8:11] = np.nan
    da = DataArray(np.linspace(0, 365, num=11), dims="time", coords={"time": time})

    if dask and has_dask:
        chunks = {"time": 5}
        da = da.chunk(chunks)

    actual = da["time"].mean()

  assert not pd.isnull(actual)

E AssertionError: assert not True E + where True = <function isna at 0x7f2475449ae8>(<xarray.DataArray 'time' ()>\narray('NaT', dtype='datetime64[ns]')) E + where <function isna at 0x7f2475449ae8> = pd.isnull

xarray/tests/test_duck_array_ops.py:288: AssertionError =============================== warnings summary ```

• [x] Closes #1232
• [x] Fully documented, including whats-new.rst for all changes and api.rst for new API (remove if this change should not be visible to users, e.g., if it is an internal clean-up, or if this is part of a larger project that will be documented later)