Some fixes

Author: dcherian

xarray/backends/zarr.py

@@ -21,7 +21,7 @@
 from xarray.backends.store import StoreBackendEntrypoint
 from xarray.core import indexing
 from xarray.core.parallelcompat import guess_chunkmanager
-from xarray.core.pycompat import integer_types
+from xarray.core.pycompat import integer_types, is_chunked_array
 from xarray.core.types import ZarrWriteModes
 from xarray.core.utils import (
     FrozenDict,
@@ -46,7 +46,7 @@ def initialize_zarr(
     ds: Dataset,
     store: MutableMapping | None = None,
     *,
-    region_dims: Iterable[Hashable] | None = None,
+    region_dims: Iterable[Hashable] = tuple(),
     mode: Literal["w", "w-"] = "w-",
     consolidated: bool | None = None,
     zarr_version: int | None = None,
@@ -90,7 +90,7 @@ def initialize_zarr(
     if "compute" in kwargs:
         raise ValueError("The ``compute`` kwarg is not supported in `initialize_zarr`.")
 
-    if not ds.chunks:
+    if not any(is_chunked_array(v._data) for v in ds._variables.values()):
         raise ValueError("This function should be used with chunked Datasets.")
 
     if mode not in ["w", "w-"]:

xarray/tests/test_backends.py

@@ -5490,6 +5490,7 @@ def test_initialize_zarr(tmp_path) -> None:
     # 4. mode = r?
     # 5. mode=w+?
     # 5. no region_dims
+    # different chunksizes along same dimension
     x = np.arange(0, 50, 10)
     y = np.arange(0, 20, 2)
     data = dask.array.ones((5, 10), chunks=(1, -1))