Drop keyword support: small fixes (#3233)

* Amended docs for new API and deprecation warnings; deprecated dropping DataArrayCoordinates (#2910).

* Removed okwarning now that docs have non-deprecated API.

* More clear warnings and more tests.

* Moved both warnings to top of function for code clarity.

* Removed unused imports.

* Update dataset.py

Author: gwgundersen

doc/indexing.rst

@@ -236,9 +236,8 @@ The :py:meth:`~xarray.Dataset.drop` method returns a new object with the listed
 index labels along a dimension dropped:
 
 .. ipython:: python
-    :okwarning:
 
-    ds.drop(['IN', 'IL'], dim='space')
+    ds.drop(space=['IN', 'IL'])
 
 ``drop`` is both a ``Dataset`` and ``DataArray`` method.
 

doc/whats-new.rst

@@ -69,7 +69,9 @@ Enhancements
   By `Ulrich Herter <https://github.com/ulijh>`_.
 
 - :py:meth:`~xarray.Dataset.drop` now supports keyword arguments; dropping index
-  labels by specifying both ``dim`` and ``labels`` is deprecated (:issue:`2910`).
+  labels by using both ``dim`` and ``labels`` or using a
+  :py:class:`~xarray.core.coordinates.DataArrayCoordinates` object are
+  deprecated (:issue:`2910`).
   By `Gregory Gundersen <https://github.com/gwgundersen/>`_.
 
 - Added examples of :py:meth:`Dataset.set_index` and

xarray/core/dataset.py

@@ -55,7 +55,6 @@
     _contains_datetime_like_objects,
 )
 from .coordinates import (
-    DataArrayCoordinates,
     DatasetCoordinates,
     LevelCoordinatesSource,
     assert_coordinate_consistent,
@@ -79,6 +78,8 @@
     either_dict_or_kwargs,
     hashable,
     maybe_wrap_array,
+    is_dict_like,
+    is_list_like,
 )
 from .variable import IndexVariable, Variable, as_variable, broadcast_variables
 
@@ -3555,9 +3556,23 @@ def drop(  # noqa: F811
         if errors not in ["raise", "ignore"]:
             raise ValueError('errors must be either "raise" or "ignore"')
 
-        labels_are_coords = isinstance(labels, DataArrayCoordinates)
-        if labels_kwargs or (utils.is_dict_like(labels) and not labels_are_coords):
-            labels_kwargs = utils.either_dict_or_kwargs(labels, labels_kwargs, "drop")
+        if is_dict_like(labels) and not isinstance(labels, dict):
+            warnings.warn(
+                "dropping coordinates using key values of dict-like labels is "
+                "deprecated; use drop_vars or a list of coordinates.",
+                FutureWarning,
+                stacklevel=2,
+            )
+        if dim is not None and is_list_like(labels):
+            warnings.warn(
+                "dropping dimensions using list-like labels is deprecated; use "
+                "dict-like arguments.",
+                DeprecationWarning,
+                stacklevel=2,
+            )
+
+        if labels_kwargs or isinstance(labels, dict):
+            labels_kwargs = either_dict_or_kwargs(labels, labels_kwargs, "drop")
             if dim is not None:
                 raise ValueError("cannot specify dim and dict-like arguments.")
             ds = self
@@ -3571,13 +3586,6 @@ def drop(  # noqa: F811
                 labels = set(labels)
             return self._drop_vars(labels, errors=errors)
         else:
-            if utils.is_list_like(labels):
-                warnings.warn(
-                    "dropping dimensions using list-like labels is deprecated; "
-                    "use dict-like arguments.",
-                    DeprecationWarning,
-                    stacklevel=2,
-                )
             return self._drop_labels(labels, dim, errors=errors)
 
     def _drop_labels(self, labels=None, dim=None, errors="raise"):

xarray/tests/test_dataset.py

@@ -2214,14 +2214,21 @@ def test_drop_labels_by_keyword(self):
         # Basic functionality.
         assert len(data.coords["x"]) == 2
 
-        # This API is allowed but deprecated.
+        # In the future, this will break.
         with pytest.warns(DeprecationWarning):
             ds1 = data.drop(["a"], dim="x")
         ds2 = data.drop(x="a")
         ds3 = data.drop(x=["a"])
         ds4 = data.drop(x=["a", "b"])
         ds5 = data.drop(x=["a", "b"], y=range(0, 6, 2))
 
+        # In the future, this will result in different behavior.
+        arr = DataArray(range(3), dims=["c"])
+        with pytest.warns(FutureWarning):
+            data.drop(arr.coords)
+        with pytest.warns(FutureWarning):
+            data.drop(arr.indexes)
+
         assert_array_equal(ds1.coords["x"], ["b"])
         assert_array_equal(ds2.coords["x"], ["b"])
         assert_array_equal(ds3.coords["x"], ["b"])