issues: 328439361

Before this fix chunksizes was dropped even when original_shape was not found in encoding

• [x] Closes #2198
• [x] Tests added (for all bug fixes or enhancements)
• [x] Tests passed (for all non-documentation changes)

Four seemingly unrelated tests failed ``` python _____________ TestEncodeCFVariable.test_missing_fillvalue ________________

self = <xarray.tests.test_conventions.TestEncodeCFVariable testMethod=test_missing_fillvalue>

def test_missing_fillvalue(self):
    v = Variable(['x'], np.array([np.nan, 1, 2, 3]))
    v.encoding = {'dtype': 'int16'}
    with pytest.warns(Warning, match='floating point data as an integer'):

      conventions.encode_cf_variable(v)

E Failed: DID NOT WARN. No warnings of type (<class 'Warning'>,) was emitted. The list of emitted warnings is: [SerializationWarning('saving variable None with floating point data as an integer dtype without any _FillValue to use for NaNs',)].

xarray/tests/test_conventions.py:89: Failed ----------------------------------------------------------------------------------------------- Captured stderr call ----------------------------------------------------------------------------------------------- /usr/lib/python3.6/site-packages/pytest/vendored_packages/pluggy.py:248: SerializationWarning: saving variable None with floating point data as an integer dtype without any _FillValue to use for NaNs call_outcome = _CallOutcome(func) _____________ TestAccessor.test_register ______________

self = <xarray.tests.test_extensions.TestAccessor testMethod=test_register>

def test_register(self):

    @xr.register_dataset_accessor('demo')
    @xr.register_dataarray_accessor('demo')
    class DemoAccessor(object):
        """Demo accessor."""

        def __init__(self, xarray_obj):
            self._obj = xarray_obj

        @property
        def foo(self):
            return 'bar'

    ds = xr.Dataset()
    assert ds.demo.foo == 'bar'

    da = xr.DataArray(0)
    assert da.demo.foo == 'bar'

    # accessor is cached
    assert ds.demo is ds.demo

    # check descriptor
    assert ds.demo.__doc__ == "Demo accessor."
    assert xr.Dataset.demo.__doc__ == "Demo accessor."
    assert isinstance(ds.demo, DemoAccessor)
    assert xr.Dataset.demo is DemoAccessor

    # ensure we can remove it
    del xr.Dataset.demo
    assert not hasattr(xr.Dataset, 'demo')

    with pytest.warns(Warning, match='overriding a preexisting attribute'):
        @xr.register_dataarray_accessor('demo')

      class Foo(object):

E Failed: DID NOT WARN. No warnings of type (<class 'Warning'>,) was emitted. The list of emitted warnings is: [AccessorRegistrationWarning("registration of accessor <class 'xarray.tests.test_extensions.TestAccessor.test_register.\<locals>.Foo'> under name 'demo' for type <class 'xarray.core.dataarray.DataArray'> is overriding a preexisting attribute with the same name.",)].

xarray/tests/test_extensions.py:60: Failed ----------------------------------------------------------------------------------------------- Captured stderr call ----------------------------------------------------------------------------------------------- /home/karel/working/xarray/xarray/tests/test_extensions.py:60: AccessorRegistrationWarning: registration of accessor <class 'xarray.tests.test_extensions.TestAccessor.test_register.\<locals>.Foo'> under name 'demo' for type <class 'xarray.core.dataarray.DataArray'> is overriding a preexisting attribute with the same name. class Foo(object): ______________ TestAlias.test ______________

self = <xarray.tests.test_utils.TestAlias testMethod=test>

def test(self):
    def new_method():
        pass
    old_method = utils.alias(new_method, 'old_method')
    assert 'deprecated' in old_method.__doc__
    with pytest.warns(Warning, match='deprecated'):

      old_method()

E Failed: DID NOT WARN. No warnings of type (<class 'Warning'>,) was emitted. The list of emitted warnings is: [FutureWarning('old_method has been deprecated. Use new_method instead.',)].

xarray/tests/test_utils.py:28: Failed ----------------------------------------------------------------------------------------------- Captured stderr call ----------------------------------------------------------------------------------------------- /home/karel/working/xarray/xarray/tests/test_utils.py:28: FutureWarning: old_method has been deprecated. Use new_method instead. old_method() _____________ TestIndexVariable.test_coordinate_alias ______________

self = <xarray.tests.test_variable.TestIndexVariable testMethod=test_coordinate_alias>

def test_coordinate_alias(self):
    with pytest.warns(Warning, match='deprecated'):

      x = Coordinate('x', [1, 2, 3])

E Failed: DID NOT WARN. No warnings of type (<class 'Warning'>,) was emitted. The list of emitted warnings is: [FutureWarning('Coordinate has been deprecated. Use IndexVariable instead.',)].

xarray/tests/test_variable.py:1763: Failed ----------------------------------------------------------------------------------------------- Captured stderr call ----------------------------------------------------------------------------------------------- /home/karel/working/xarray/xarray/tests/test_variable.py:1763: FutureWarning: Coordinate has been deprecated. Use IndexVariable instead. x = Coordinate('x', [1, 2, 3]) ```