Make broadcast and concat work with the Array API (#7387)

* Make `broadcast` and `concat` work with the Array API.

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: tomwhite

xarray/core/duck_array_ops.py

@@ -16,8 +16,8 @@
 import pandas as pd
 from numpy import all as array_all  # noqa
 from numpy import any as array_any  # noqa
+from numpy import around  # noqa
 from numpy import zeros_like  # noqa
-from numpy import around, broadcast_to  # noqa
 from numpy import concatenate as _concatenate
 from numpy import (  # noqa
     einsum,
@@ -207,6 +207,11 @@ def as_shared_dtype(scalars_or_arrays, xp=np):
     return [astype(x, out_type, copy=False) for x in arrays]
 
 
+def broadcast_to(array, shape):
+    xp = get_array_namespace(array)
+    return xp.broadcast_to(array, shape)
+
+
 def lazy_array_equiv(arr1, arr2):
     """Like array_equal, but doesn't actually compare values.
     Returns True when arr1, arr2 identical or their dask tokens are equal.
@@ -311,6 +316,9 @@ def fillna(data, other):
 
 def concatenate(arrays, axis=0):
     """concatenate() with better dtype promotion rules."""
+    if hasattr(arrays[0], "__array_namespace__"):
+        xp = get_array_namespace(arrays[0])
+        return xp.concat(as_shared_dtype(arrays, xp=xp), axis=axis)
     return _concatenate(as_shared_dtype(arrays), axis=axis)
 
 

xarray/tests/test_array_api.py

@@ -64,6 +64,27 @@ def test_astype(arrays) -> None:
     assert_equal(actual, expected)
 
 
+def test_broadcast(arrays: tuple[xr.DataArray, xr.DataArray]) -> None:
+    np_arr, xp_arr = arrays
+    np_arr2 = xr.DataArray(np.array([1.0, 2.0]), dims="x")
+    xp_arr2 = xr.DataArray(xp.asarray([1.0, 2.0]), dims="x")
+
+    expected = xr.broadcast(np_arr, np_arr2)
+    actual = xr.broadcast(xp_arr, xp_arr2)
+    assert len(actual) == len(expected)
+    for a, e in zip(actual, expected):
+        assert isinstance(a.data, Array)
+        assert_equal(a, e)
+
+
+def test_concat(arrays: tuple[xr.DataArray, xr.DataArray]) -> None:
+    np_arr, xp_arr = arrays
+    expected = xr.concat((np_arr, np_arr), dim="x")
+    actual = xr.concat((xp_arr, xp_arr), dim="x")
+    assert isinstance(actual.data, Array)
+    assert_equal(actual, expected)
+
+
 def test_indexing(arrays: tuple[xr.DataArray, xr.DataArray]) -> None:
     np_arr, xp_arr = arrays
     expected = np_arr[:, 0]