combine_by_coordinates to handle unnamed data arrays.

doc/whats-new.rst

@@ -21,16 +21,11 @@ v0.18.2 (unreleased)
 
 New Features
 ~~~~~~~~~~~~
-- :py:func:`combine_by_coords` now accepts a list of unnamed ``DataArray`` as input (:issue:`3248`, :pull:`4696`).
-  By `Augustus Ijams <https://github.com/aijams>`_.
 
 
 Breaking changes
 ~~~~~~~~~~~~~~~~
-- The main parameter to :py:func:`combine_by_coords` is renamed to `data_objects` instead
-  of `datasets` so anyone calling this method using a named parameter will need to update
-  the name accordingly (:issue:`3248`, :pull:`4696`).
-  By `Augustus Ijams <https://github.com/aijams>`_.
+
 
 Deprecations
 ~~~~~~~~~~~~
@@ -65,7 +60,6 @@ Thomas Nicholas, Tom Nicholas, Zachary Moon.
 
 New Features
 ~~~~~~~~~~~~
-
 - Implement :py:meth:`DataArray.drop_duplicates`
   to remove duplicate dimension values (:pull:`5239`).
   By `Andrew Huang <https://github.com/ahuang11>`_.
@@ -78,9 +72,22 @@ New Features
 - Raise more informative error when decoding time variables with invalid reference dates.
   (:issue:`5199`, :pull:`5288`). By `Giacomo Caria <https://github.com/gcaria>`_.
 
+Breaking changes
+~~~~~~~~~~~~~~~~
+- The main parameter to :py:func:`combine_by_coords` is renamed to `data_objects` instead
+  of `datasets` so anyone calling this method using a named parameter will need to update
+  the name accordingly (:issue:`3248`, :pull:`4696`).
+  By `Augustus Ijams <https://github.com/aijams>`_.
+
+Deprecations
+~~~~~~~~~~~~
+
+
 Bug fixes
 ~~~~~~~~~
-
+- :py:func:`combine_by_coords` can now handle combining a list of unnamed
+  ``DataArray`` as input (:issue:`3248`, :pull:`4696`).
+  By `Augustus Ijams <https://github.com/aijams>`_.
 - Opening netCDF files from a path that doesn't end in ``.nc`` without supplying
   an explicit ``engine`` works again (:issue:`5295`), fixing a bug introduced in
   0.18.0.

xarray/core/combine.py

@@ -1,4 +1,5 @@
 import itertools
+import warnings
 from collections import Counter
 
 import pandas as pd
@@ -10,6 +11,7 @@
 from .merge import merge
 from .utils import iterate_nested
 
+
 def _infer_concat_order_from_positions(datasets):
     return dict(_infer_tile_ids_from_nested_list(datasets, ()))
 
@@ -310,6 +312,7 @@ def _new_tile_id(single_id_ds_pair):
     tile_id, ds = single_id_ds_pair
     return tile_id[1:]
 
+
 def _nested_combine(
     datasets,
     concat_dims,
@@ -351,6 +354,7 @@ def _nested_combine(
     )
     return combined
 
+
 def combine_nested(
     datasets,
     concat_dim,
@@ -541,7 +545,8 @@ def combine_nested(
     mixed_datasets_and_arrays = any(
         isinstance(obj, Dataset) for obj in iterate_nested(datasets)
     ) and any(
-        isinstance(obj, DataArray) and obj.name is None for obj in iterate_nested(datasets)
+        isinstance(obj, DataArray) and obj.name is None
+        for obj in iterate_nested(datasets)
     )
     if mixed_datasets_and_arrays:
         raise ValueError("Can't combine datasets with unnamed arrays.")
@@ -626,15 +631,16 @@ def _combine_single_variable_hypercube(
     return concatenated
 
 
+# TODO remove empty list default param after version 0.19, see PR4696
 def combine_by_coords(
-    data_objects,
+    data_objects=[],
     compat="no_conflicts",
     data_vars="all",
     coords="different",
     fill_value=dtypes.NA,
     join="outer",
     combine_attrs="no_conflicts",
-    datasets=None
+    datasets=None,
 ):
     """
     Attempt to auto-magically combine the given datasets (or data arrays)
@@ -840,7 +846,8 @@ def combine_by_coords(
     if datasets is not None:
         warnings.warn(
             "The datasets argument has been renamed to `data_objects`."
-            " In future passing a value for datasets will raise an error.")
+            " In future passing a value for datasets will raise an error."
+        )
         data_objects = datasets
 
     if not data_objects:
@@ -849,9 +856,7 @@ def combine_by_coords(
     mixed_arrays_and_datasets = any(
         isinstance(data_object, DataArray) and data_object.name is None
         for data_object in data_objects
-    ) and any(
-        isinstance(data_object, Dataset) for data_object in data_objects
-    )
+    ) and any(isinstance(data_object, Dataset) for data_object in data_objects)
     if mixed_arrays_and_datasets:
         raise ValueError("Can't automatically combine datasets with unnamed arrays.")
 

xarray/core/utils.py

@@ -933,6 +933,7 @@ class Default(Enum):
 
 _default = Default.token
 
+
 def iterate_nested(nested_list):
     for item in nested_list:
         if isinstance(item, list):

xarray/tests/test_combine.py

@@ -680,11 +680,11 @@ def test_nested_combine_mixed_datasets_arrays(self):
             Dataset({"x": [2, 3]}),
         ]
         with pytest.raises(
-                ValueError,
-                match=r"Can't combine datasets with unnamed arrays."
-            ):
+            ValueError, match=r"Can't combine datasets with unnamed arrays."
+        ):
             combine_nested(objs, "x")
 
+
 class TestCombineAuto:
     def test_combine_by_coords(self):
         objs = [Dataset({"x": [0]}), Dataset({"x": [1]})]
@@ -733,9 +733,9 @@ def test_combine_coords_mixed_datasets_arrays(self):
             Dataset({"x": [2, 3]}),
         ]
         with pytest.raises(
-                ValueError,
-                match=r"Can't automatically combine datasets with unnamed arrays."
-            ):
+            ValueError,
+            match=r"Can't automatically combine datasets with unnamed arrays.",
+        ):
             combine_by_coords(objs)
 
     @pytest.mark.parametrize(

xarray/tests/test_utils.py

@@ -322,6 +322,7 @@ def test_infix_dims_errors(supplied, all_):
     with pytest.raises(ValueError):
         list(utils.infix_dims(supplied, all_))
 
+
 @pytest.mark.parametrize(
     "nested_list, expected",
     [
@@ -330,8 +331,8 @@ def test_infix_dims_errors(supplied, all_):
         ([1, 2, 3], [1, 2, 3]),
         ([[1]], [1]),
         ([[1, 2], [3, 4]], [1, 2, 3, 4]),
-        ([[[1, 2, 3], [4]], [5, 6]], [1, 2, 3, 4, 5, 6])
-    ]
+        ([[[1, 2, 3], [4]], [5, 6]], [1, 2, 3, 4, 5, 6]),
+    ],
 )
 def test_iterate_nested(nested_list, expected):
-    assert list(iterate_nested(nested_list)) == expected
+    assert list(iterate_nested(nested_list)) == expected