variable.py as_compatible_data: disallow DataArrays (pydata#4493)

* variable.py as_compatible_data: allow DataArrays too

* variable.py: as_compatible_data: DataArray raise TypeError

tell user to use da.data

* variable.py: as_compatible_data: debug syntax

* variable.py: update no .data error msg

* move err msg to as_variable

* whats-new changelog

* stylistic debug

* whats-new.rst move changelog to new unreleased version

* debug formatting whats-new.rst

* add .data to tests using tuples

* fix test_dask.py test

* fix test_dataset

* raise DeprecationWarning instead of TypeError

* add .data to the example in plotting

* state when the warning will be turned into an error

* small fix [skip-ci]

* check that as_variable warns correctly

* warn instead of raising the warning

* fix the test

* manually extract the data

* use a single statement to modify obj

* remove the extraction of the data altogether

Co-authored-by: chunhochow <[email protected]>
Co-authored-by: Keewis <[email protected]>

Author: chunhochow

doc/plotting.rst

@@ -227,7 +227,7 @@ from the time and assign it as a non-dimension coordinate:
     :okwarning:
 
     decimal_day = (air1d.time - air1d.time[0]) / pd.Timedelta("1d")
-    air1d_multi = air1d.assign_coords(decimal_day=("time", decimal_day))
+    air1d_multi = air1d.assign_coords(decimal_day=("time", decimal_day.data))
     air1d_multi
 
 To use ``'decimal_day'`` as x coordinate it must be explicitly specified:

doc/whats-new.rst

@@ -128,6 +128,9 @@ Bug fixes
 - Expand user directory paths (e.g. ``~/``) in :py:func:`open_mfdataset` and
   :py:meth:`Dataset.to_zarr` (:issue:`4783`, :pull:`4795`).
   By `Julien Seguinot <https://github.com/juseg>`_.
+- Raise DeprecationWarning when trying to typecast a tuple containing a :py:class:`DataArray`.
+  User now prompted to first call `.data` on it (:issue:`4483`).
+  By `Chun Ho Chow <https://github.com/chunhochow>`_.
 - Add :py:meth:`Dataset.drop_isel` and :py:meth:`DataArray.drop_isel` (:issue:`4658`, :pull:`4819`). By `Daniel Mesejo <https://github.com/mesejo>`_.
 - Ensure that :py:meth:`Dataset.interp` raises ``ValueError`` when interpolating outside coordinate range and ``bounds_error=True`` (:issue:`4854`, :pull:`4855`).
   By `Leif Denby <https://github.com/leifdenby>`_.

xarray/core/variable.py

@@ -120,6 +120,16 @@ def as_variable(obj, name=None) -> "Union[Variable, IndexVariable]":
     if isinstance(obj, Variable):
         obj = obj.copy(deep=False)
     elif isinstance(obj, tuple):
+        if isinstance(obj[1], DataArray):
+            # TODO: change into TypeError
+            warnings.warn(
+                (
+                    "Using a DataArray object to construct a variable is"
+                    " ambiguous, please extract the data using the .data property."
+                    " This will raise a TypeError in 0.19.0."
+                ),
+                DeprecationWarning,
+            )
         try:
             obj = Variable(*obj)
         except (TypeError, ValueError) as error:

xarray/tests/test_dask.py

@@ -1233,7 +1233,7 @@ def test_map_blocks_to_array(map_ds):
         lambda x: x.drop_vars("x"),
         lambda x: x.expand_dims(k=[1, 2, 3]),
         lambda x: x.expand_dims(k=3),
-        lambda x: x.assign_coords(new_coord=("y", x.y * 2)),
+        lambda x: x.assign_coords(new_coord=("y", x.y.data * 2)),
         lambda x: x.astype(np.int32),
         lambda x: x.x,
     ],

xarray/tests/test_dataset.py

@@ -4959,13 +4959,13 @@ def test_reduce_keepdims(self):
         # Coordinates involved in the reduction should be removed
         actual = ds.mean(keepdims=True)
         expected = Dataset(
-            {"a": (["x", "y"], np.mean(ds.a, keepdims=True))}, coords={"c": ds.c}
+            {"a": (["x", "y"], np.mean(ds.a, keepdims=True).data)}, coords={"c": ds.c}
         )
         assert_identical(expected, actual)
 
         actual = ds.mean("x", keepdims=True)
         expected = Dataset(
-            {"a": (["x", "y"], np.mean(ds.a, axis=0, keepdims=True))},
+            {"a": (["x", "y"], np.mean(ds.a, axis=0, keepdims=True).data)},
             coords={"y": ds.y, "c": ds.c},
         )
         assert_identical(expected, actual)

xarray/tests/test_interp.py

@@ -190,7 +190,7 @@ def func(obj, dim, new_x):
             "w": xdest["w"],
             "z2": xdest["z2"],
             "y": da["y"],
-            "x": (("z", "w"), xdest),
+            "x": (("z", "w"), xdest.data),
             "x2": (("z", "w"), func(da["x2"], "x", xdest)),
         },
     )

xarray/tests/test_variable.py

@@ -8,7 +8,7 @@
 import pytest
 import pytz
 
-from xarray import Coordinate, Dataset, IndexVariable, Variable, set_options
+from xarray import Coordinate, DataArray, Dataset, IndexVariable, Variable, set_options
 from xarray.core import dtypes, duck_array_ops, indexing
 from xarray.core.common import full_like, ones_like, zeros_like
 from xarray.core.indexing import (
@@ -1081,6 +1081,9 @@ def test_as_variable(self):
         td = np.array([timedelta(days=x) for x in range(10)])
         assert as_variable(td, "time").dtype.kind == "m"
 
+        with pytest.warns(DeprecationWarning):
+            as_variable(("x", DataArray([])))
+
     def test_repr(self):
         v = Variable(["time", "x"], [[1, 2, 3], [4, 5, 6]], {"foo": "bar"})
         expected = dedent(