remove warning, and instead error when creating v3 arrays with storage transformers

Author: d-v-b

src/zarr/core/array.py

@@ -79,7 +79,14 @@ def parse_array_metadata(data: Any) -> ArrayV2Metadata | ArrayV3Metadata:
         return data
     elif isinstance(data, dict):
         if data["zarr_format"] == 3:
-            return ArrayV3Metadata.from_dict(data)
+            meta_out = ArrayV3Metadata.from_dict(data)
+            if len(meta_out.storage_transformers) > 0:
+                msg = (
+                    f"Array metadata contains storage transformers: {meta_out.storage_transformers}."
+                    "Arrays with storage transformers are not supported in zarr-python at this time."
+                )
+                raise ValueError(msg)
+            return meta_out
         elif data["zarr_format"] == 2:
             return ArrayV2Metadata.from_dict(data)
     raise TypeError

src/zarr/core/metadata/v3.py

@@ -1,6 +1,5 @@
 from __future__ import annotations
 
-import warnings
 from typing import TYPE_CHECKING, cast, overload
 
 if TYPE_CHECKING:
@@ -72,24 +71,20 @@ def parse_dimension_names(data: object) -> tuple[str | None, ...] | None:
 
 
 def parse_storage_transformers(data: object) -> tuple[dict[str, JSON], ...]:
+    """
+    Parse storage_transformers. Zarr python cannot use storage transformers
+    at this time, so this function doesn't attempt to validate them.
+    """
     if data is None:
         return ()
     if isinstance(data, Iterable):
         if len(tuple(data)) >= 1:
-            msg = (
-                "Got a non-null storage_transformers keyword argument. "
-                "Storage transformers are not supported by zarr-python at this time. "
-                "The storage transformer(s) will be retained in array metadata but will not "
-                "influence storage routines"
-            )
-            warnings.warn(msg, UserWarning, stacklevel=1)
             return data  # type: ignore[return-value]
         else:
             return ()
-    else:
-        raise TypeError(
-            f"Invalid storage_transformers. Expected an iterable of dicts. Got {type(data)} instead."
-        )
+    raise TypeError(
+        f"Invalid storage_transformers. Expected an iterable of dicts. Got {type(data)} instead."
+    )
 
 
 @dataclass(frozen=True, kw_only=True)

tests/v3/test_array.py

@@ -5,7 +5,8 @@
 import pytest
 
 from zarr import Array, AsyncArray, Group
-from zarr.core.common import ZarrFormat
+from zarr.codecs.bytes import BytesCodec
+from zarr.core.common import JSON, ZarrFormat
 from zarr.errors import ContainsArrayError, ContainsGroupError
 from zarr.store import LocalStore, MemoryStore
 from zarr.store.common import StorePath
@@ -188,3 +189,24 @@ def test_serializable_sync_array(store: LocalStore, zarr_format: ZarrFormat) ->
 
     assert actual == expected
     np.testing.assert_array_equal(actual[:], expected[:])
+
+
+@pytest.mark.parametrize("store", ("memory",), indirect=True)
+def test_storage_transformers(store: MemoryStore) -> None:
+    """
+    Test that providing an actual storage transformer produces a warning and otherwise passes through
+    """
+    metadata_dict: dict[str, JSON] = {
+        "zarr_format": 3,
+        "node_type": "array",
+        "shape": (10,),
+        "chunk_grid": {"name": "regular", "configuration": {"chunk_shape": (1,)}},
+        "data_type": "uint8",
+        "chunk_key_encoding": {"name": "v2", "configuration": {"separator": "/"}},
+        "codecs": (BytesCodec().to_dict(),),
+        "fill_value": 0,
+        "storage_transformers": ({"test": "should_raise"}),
+    }
+    match = "Arrays with storage transformers are not supported in zarr-python at this time."
+    with pytest.raises(ValueError, match=match):
+        Array.from_dict(StorePath(store), data=metadata_dict)

tests/v3/test_metadata/test_v3.py

@@ -264,24 +264,3 @@ async def test_datetime_metadata(fill_value: int, precision: str) -> None:
 
     result = json.loads(d["zarr.json"].to_bytes())
     assert result["fill_value"] == fill_value
-
-
-def test_storage_transformers() -> None:
-    """
-    Test that providing an actual storage transformer produces a warning and otherwise passes through
-    """
-    metadata_dict = {
-        "zarr_format": 3,
-        "node_type": "array",
-        "shape": (10,),
-        "chunk_grid": {"name": "regular", "configuration": {"chunk_shape": (1,)}},
-        "data_type": "uint8",
-        "chunk_key_encoding": {"name": "v2", "configuration": {"separator": "/"}},
-        "codecs": (BytesCodec(),),
-        "fill_value": 0,
-        "storage_transformers": ({"test": "should_warn"}),
-    }
-    with pytest.warns():
-        meta = ArrayV3Metadata.from_dict(metadata_dict)
-
-    assert meta.to_dict()["storage_transformers"] == metadata_dict["storage_transformers"]