remove vestigial use of to_dtype().itemsize()

Author: d-v-b

src/zarr/core/array.py

@@ -4197,7 +4197,7 @@ async def init_array(
 
     from zarr.codecs.sharding import ShardingCodec, ShardingCodecIndexLocation
 
-    dtype_wrapped = parse_data_type(dtype, zarr_format=zarr_format)
+    zdtype = parse_data_type(dtype, zarr_format=zarr_format)
     shape_parsed = parse_shapelike(shape)
     chunk_key_encoding_parsed = _parse_chunk_key_encoding(
         chunk_key_encoding, zarr_format=zarr_format
@@ -4211,11 +4211,15 @@ async def init_array(
     else:
         await ensure_no_existing_node(store_path, zarr_format=zarr_format)
 
+    item_size = 1
+    if isinstance(zdtype, HasItemSize):
+        item_size = zdtype.item_size
+
     shard_shape_parsed, chunk_shape_parsed = _auto_partition(
         array_shape=shape_parsed,
         shard_shape=shards,
         chunk_shape=chunks,
-        item_size=dtype_wrapped.to_dtype().itemsize,
+        item_size=item_size,
     )
     chunks_out: tuple[int, ...]
     meta: ArrayV2Metadata | ArrayV3Metadata
@@ -4231,7 +4235,7 @@ async def init_array(
             raise ValueError("Zarr format 2 arrays do not support `serializer`.")
 
         filters_parsed, compressor_parsed = _parse_chunk_encoding_v2(
-            compressor=compressors, filters=filters, dtype=dtype_wrapped
+            compressor=compressors, filters=filters, dtype=zdtype
         )
         if dimension_names is not None:
             raise ValueError("Zarr format 2 arrays do not support dimension names.")
@@ -4242,7 +4246,7 @@ async def init_array(
 
         meta = AsyncArray._create_metadata_v2(
             shape=shape_parsed,
-            dtype=dtype_wrapped,
+            dtype=zdtype,
             chunks=chunk_shape_parsed,
             dimension_separator=chunk_key_encoding_parsed.separator,
             fill_value=fill_value,
@@ -4256,7 +4260,7 @@ async def init_array(
             compressors=compressors,
             filters=filters,
             serializer=serializer,
-            dtype=dtype_wrapped,
+            dtype=zdtype,
         )
         sub_codecs = cast(tuple[Codec, ...], (*array_array, array_bytes, *bytes_bytes))
         codecs_out: tuple[Codec, ...]
@@ -4271,7 +4275,7 @@ async def init_array(
             )
             sharding_codec.validate(
                 shape=chunk_shape_parsed,
-                dtype=dtype_wrapped,
+                dtype=zdtype,
                 chunk_grid=RegularChunkGrid(chunk_shape=shard_shape_parsed),
             )
             codecs_out = (sharding_codec,)
@@ -4287,7 +4291,7 @@ async def init_array(
 
         meta = AsyncArray._create_metadata_v3(
             shape=shape_parsed,
-            dtype=dtype_wrapped,
+            dtype=zdtype,
             fill_value=fill_value,
             chunk_shape=chunks_out,
             chunk_key_encoding=chunk_key_encoding_parsed,