chore: no warning if target shard size is set with auto

Author: ilan-gold

src/zarr/core/chunk_grids.py

@@ -756,13 +756,15 @@ def _auto_partition(
             _chunks_out = chunk_shape
 
         if shard_shape == "auto":
-            warnings.warn(
-                "Automatic shard shape inference is experimental and may change without notice.",
-                ZarrUserWarning,
-                stacklevel=2,
-            )
             _shards_out = ()
             target_shard_size_bytes = zarr.config.get("array.target_shard_size_bytes", None)
+            if target_shard_size_bytes is None:
+                warnings.warn(
+                    "Automatic shard shape inference is experimental and may change without notice."
+                    "To set a target uncompressed shard size, use zarr.config.array.target_shard_size_bytes.",
+                    ZarrUserWarning,
+                    stacklevel=2,
+                )
             num_chunks_per_shard_axis = (
                 _guess_num_chunks_per_axis_shard(
                     chunk_shape=_chunks_out,

tests/test_array.py

@@ -1073,35 +1073,27 @@ def test_auto_partition_auto_shards(
     where there are 8 or more chunks.
     """
     dtype = np.dtype("uint8")
-    with pytest.warns(
-        ZarrUserWarning,
-        match="Automatic shard shape inference is experimental and may change without notice.",
-    ):
-        with zarr.config.set({"array.target_shard_size_bytes": target_shard_size_bytes}):
-            auto_shards, _ = _auto_partition(
-                array_shape=array_shape,
-                chunk_shape=chunk_shape,
-                shard_shape="auto",
-                item_size=dtype.itemsize,
-            )
+    with zarr.config.set({"array.target_shard_size_bytes": target_shard_size_bytes}):
+        auto_shards, _ = _auto_partition(
+            array_shape=array_shape,
+            chunk_shape=chunk_shape,
+            shard_shape="auto",
+            item_size=dtype.itemsize,
+        )
     assert auto_shards == expected_shards
 
 
 def test_auto_partition_auto_shards_with_auto_chunks_should_be_close_to_1MiB() -> None:
     """
     Test that automatically picking a shard size and a chunk size gives roughly 1MiB chunks.
     """
-    with pytest.warns(
-        ZarrUserWarning,
-        match="Automatic shard shape inference is experimental and may change without notice.",
-    ):
-        with zarr.config.set({"array.target_shard_size_bytes": 10_000_000}):
-            _, chunk_shape = _auto_partition(
-                array_shape=(10_000_000,),
-                chunk_shape="auto",
-                shard_shape="auto",
-                item_size=1,
-            )
+    with zarr.config.set({"array.target_shard_size_bytes": 10_000_000}):
+        _, chunk_shape = _auto_partition(
+            array_shape=(10_000_000,),
+            chunk_shape="auto",
+            shard_shape="auto",
+            item_size=1,
+        )
     assert chunk_shape == (625000,)