Add IndexingAdapter mixin class

Author: dcherian

xarray/core/indexing.py

@@ -520,8 +520,7 @@ class ExplicitlyIndexedNDArrayMixin(NDArrayMixin, ExplicitlyIndexed):
     __slots__ = ()
 
     def get_duck_array(self):
-        key = BasicIndexer((slice(None),) * self.ndim)
-        return self[key]
+        raise NotImplementedError
 
     def _oindex_get(self, indexer: OuterIndexer):
         raise NotImplementedError(
@@ -559,6 +558,17 @@ def vindex(self) -> IndexCallable:
         return IndexCallable(self._vindex_get, self._vindex_set)
 
 
+class IndexingAdapter:
+    """Marker class for indexing adapters.
+    These classes translate between Xarray's indexing semantics and the underlying array's
+    indexing semantics.
+    """
+
+    def get_duck_array(self):
+        key = BasicIndexer((slice(None),) * self.ndim)
+        return self[key]
+
+
 class ImplicitToExplicitIndexingAdapter(NDArrayMixin):
     """Wrap an array, converting tuples into the indicated explicit indexer."""
 
@@ -1527,7 +1537,7 @@ def is_fancy_indexer(indexer: Any) -> bool:
     return True
 
 
-class NumpyIndexingAdapter(ExplicitlyIndexedNDArrayMixin):
+class NumpyIndexingAdapter(IndexingAdapter, ExplicitlyIndexedNDArrayMixin):
     """Wrap a NumPy array to use explicit indexing."""
 
     __slots__ = ("array",)
@@ -1606,7 +1616,7 @@ def __init__(self, array):
         self.array = array
 
 
-class ArrayApiIndexingAdapter(ExplicitlyIndexedNDArrayMixin):
+class ArrayApiIndexingAdapter(IndexingAdapter, ExplicitlyIndexedNDArrayMixin):
     """Wrap an array API array to use explicit indexing."""
 
     __slots__ = ("array",)
@@ -1671,7 +1681,7 @@ def _assert_not_chunked_indexer(idxr: tuple[Any, ...]) -> None:
         )
 
 
-class DaskIndexingAdapter(ExplicitlyIndexedNDArrayMixin):
+class DaskIndexingAdapter(IndexingAdapter, ExplicitlyIndexedNDArrayMixin):
     """Wrap a dask array to support explicit indexing."""
 
     __slots__ = ("array",)
@@ -1747,7 +1757,7 @@ def transpose(self, order):
         return self.array.transpose(order)
 
 
-class PandasIndexingAdapter(ExplicitlyIndexedNDArrayMixin):
+class PandasIndexingAdapter(IndexingAdapter, ExplicitlyIndexedNDArrayMixin):
     """Wrap a pandas.Index to preserve dtypes and handle explicit indexing."""
 
     __slots__ = ("_dtype", "array")
@@ -2068,7 +2078,9 @@ def copy(self, deep: bool = True) -> Self:
         return type(self)(array, self._dtype, self.level)
 
 
-class CoordinateTransformIndexingAdapter(ExplicitlyIndexedNDArrayMixin):
+class CoordinateTransformIndexingAdapter(
+    IndexingAdapter, ExplicitlyIndexedNDArrayMixin
+):
     """Wrap a CoordinateTransform as a lazy coordinate array.
 
     Supports explicit indexing (both outer and vectorized).