Support implicit array conversion with query-planning enabled (#15378)

when query-planning is enabled, implicit conversion is not yet supported from a cudf-backed collection to a dask array. [Some cuml + dask CI failures are related to this limitation](rapidsai/cuml#5815 (comment)). This PR adds basic support for implicit conversion.

Authors:
  - Richard (Rick) Zamora (https://github.com/rjzamora)

Approvers:
  - Lawrence Mitchell (https://github.com/wence-)

URL: #15378

Author: rjzamora

python/dask_cudf/dask_cudf/expr/_collection.py

@@ -108,3 +108,34 @@ class Index(DXIndex):
 get_collection_type.register(cudf.DataFrame, lambda _: DataFrame)
 get_collection_type.register(cudf.Series, lambda _: Series)
 get_collection_type.register(cudf.BaseIndex, lambda _: Index)
+
+
+##
+## Support conversion to GPU-backed Array collections
+##
+
+
+try:
+    from dask_expr._backends import create_array_collection
+
+    @get_collection_type.register_lazy("cupy")
+    def _register_cupy():
+        import cupy
+
+        @get_collection_type.register(cupy.ndarray)
+        def get_collection_type_cupy_array(_):
+            return create_array_collection
+
+    @get_collection_type.register_lazy("cupyx")
+    def _register_cupyx():
+        # Needed for cuml
+        from cupyx.scipy.sparse import spmatrix
+
+        @get_collection_type.register(spmatrix)
+        def get_collection_type_csr_matrix(_):
+            return create_array_collection
+
+except ImportError:
+    # Older version of dask-expr.
+    # Implicit conversion to array wont work.
+    pass

python/dask_cudf/dask_cudf/tests/test_core.py

@@ -913,3 +913,37 @@ def test_categorical_dtype_round_trip():
     actual = ds.compute()
     expected = pds.compute()
     assert actual.dtype.ordered == expected.dtype.ordered
+
+
+def test_implicit_array_conversion_cupy():
+    s = cudf.Series(range(10))
+    ds = dask_cudf.from_cudf(s, npartitions=2)
+
+    def func(x):
+        return x.values
+
+    # Need to compute the dask collection for now.
+    # See: https://github.com/dask/dask/issues/11017
+    result = ds.map_partitions(func, meta=s.values).compute()
+    expect = func(s)
+
+    dask.array.assert_eq(result, expect)
+
+
+def test_implicit_array_conversion_cupy_sparse():
+    cupyx = pytest.importorskip("cupyx")
+
+    s = cudf.Series(range(10), dtype="float32")
+    ds = dask_cudf.from_cudf(s, npartitions=2)
+
+    def func(x):
+        return cupyx.scipy.sparse.csr_matrix(x.values)
+
+    # Need to compute the dask collection for now.
+    # See: https://github.com/dask/dask/issues/11017
+    result = ds.map_partitions(func, meta=s.values).compute()
+    expect = func(s)
+
+    # NOTE: The calculation here doesn't need to make sense.
+    # We just need to make sure we get the right type back.
+    assert type(result) == type(expect)