Add default value to init_array config param. Update docstring. (#3391)

* Make config in init_array optional

 * Add default value to init_array config param.
 * Update docstring.
 * Add changelog entry.
 * Fix type casting typo.

* Update src/zarr/core/array.py

* Update src/zarr/core/array.py

* reformat docstring

---------

Co-authored-by: Davis Bennett <davis.v.bennett@gmail.com>

Author: kgabor

changes/3391.feature.rst

@@ -0,0 +1 @@
+Make config param optional in init_array

src/zarr/core/array.py

@@ -4444,7 +4444,7 @@ async def init_array(
     chunk_key_encoding: ChunkKeyEncodingLike | None = None,
     dimension_names: DimensionNames = None,
     overwrite: bool = False,
-    config: ArrayConfigLike | None,
+    config: ArrayConfigLike | None = None,
 ) -> AsyncArray[ArrayV3Metadata] | AsyncArray[ArrayV2Metadata]:
     """Create and persist an array metadata document.
 
@@ -4524,8 +4524,10 @@ async def init_array(
         Zarr format 3 only. Zarr format 2 arrays should not use this parameter.
     overwrite : bool, default False
         Whether to overwrite an array with the same name in the store, if one exists.
-    config : ArrayConfigLike or None, optional
+    config : ArrayConfigLike or None, default=None
         Configuration for this array.
+        If  ``None``, the default array runtime configuration will be used. This default
+        is stored in the global configuration object.
 
     Returns
     -------

src/zarr/testing/utils.py

@@ -46,4 +46,4 @@ def has_cupy() -> bool:
 
 # Decorator for GPU tests
 def gpu_test(func: T) -> T:
-    return cast("T", gpu_mark(skip_if_no_gpu(func)))
+    return cast(T, gpu_mark(skip_if_no_gpu(func)))

tests/test_api.py

@@ -440,7 +440,6 @@ async def test_init_order_warns() -> None:
             store_path=StorePath(store=MemoryStore()),
             shape=(1,),
             dtype="uint8",
-            config=None,
             zarr_format=3,
             order="F",
         )