proper fix

Author: LDeakin

src/zarr/codecs/sharding.py

@@ -481,12 +481,8 @@ async def _decode_partial_single(
         )
 
         # setup output array
-        if hasattr(indexer, "sel_shape"):
-            out_shape = indexer.sel_shape
-        else:
-            out_shape = indexer.shape
         out = shard_spec.prototype.nd_buffer.create(
-            shape=out_shape, dtype=shard_spec.dtype, order=shard_spec.order, fill_value=0
+            shape=indexer.shape, dtype=shard_spec.dtype, order=shard_spec.order, fill_value=0
         )
 
         indexed_chunks = list(indexer)
@@ -533,7 +529,11 @@ async def _decode_partial_single(
             ],
             out,
         )
-        return out
+
+        if hasattr(indexer, "sel_shape"):
+            return out.reshape(indexer.sel_shape)
+        else:
+            return out
 
     async def _encode_single(
         self,

tests/test_array.py

@@ -1427,11 +1427,11 @@ async def test_sharding_coordinate_selection() -> None:
     g = zarr.open_group(store, mode="w")
     arr = g.create_array(
         name="a",
-        shape=(10, 20, 30),
-        chunks=(5, 1, 30),
+        shape=(2, 3, 4),
+        chunks=(1, 2, 2),
         overwrite=True,
         dtype=np.float32,
-        shards=(5, 20, 30),
+        shards=(2, 4, 4),
     )
-    arr[:] = np.arange(10*20*30).reshape((10, 20, 30))
-    assert (arr[5, [0, 1]] == np.vstack([np.arange(3000, 3030), np.arange(3030, 3060)])).all()
+    arr[:] = np.arange(2 * 3 * 4).reshape((2, 3, 4))
+    assert (arr[1, [0, 1]] == np.array([[12, 13, 14, 15], [16, 17, 18, 19]])).all()