relax endianness mismatch to a warning instead of an error

Author: d-v-b

src/zarr/core/array.py

@@ -4382,9 +4382,9 @@ def _parse_chunk_encoding_v3(
         ):
             msg = (
                 f"The endianness of the requested serializer ({out_array_bytes}) does not match the endianness of the dtype ({dtype.endianness}). "
-                "The endianness of the serializer and the dtype must match."
+                "In this situation the serializer's endianness takes priority. To avoid this warning, ensure the endianness of the serializer matches the endianness of the dtype."
             )
-            raise ValueError(msg)
+            warnings.warn(msg, UserWarning, stacklevel=2)
 
     if compressors is None:
         out_bytes_bytes: tuple[BytesBytesCodec, ...] = ()

tests/test_array.py

@@ -1349,10 +1349,11 @@ def test_explicit_endianness(store: Store, endianness: Endianness) -> None:
 
         msg = (
             f"The endianness of the requested serializer ({serializer}) does not match the endianness of the dtype ({dtype.endianness}). "
-            "The endianness of the serializer and the dtype must match."
+            "In this situation the serializer's endianness takes priority. "
+            "To avoid this warning, ensure the endianness of the serializer matches the endianness of the dtype."
         )
 
-        with pytest.raises(ValueError, match=re.escape(msg)):
+        with pytest.warns(UserWarning, match=re.escape(msg)):
             _ = zarr.create_array(
                 store=store,
                 shape=(1,),
@@ -1361,22 +1362,6 @@ def test_explicit_endianness(store: Store, endianness: Endianness) -> None:
                 serializer=serializer,
             )
 
-        # additional check for the case where the serializer has endian=None
-        none_serializer = dataclasses.replace(serializer, endian=None)
-        msg = (
-            f"The endianness of the requested serializer ({none_serializer}) does not match the endianness of the dtype ({dtype.endianness}). "
-            "The endianness of the serializer and the dtype must match."
-        )
-
-        with pytest.raises(ValueError, match=re.escape(msg)):
-            _ = zarr.create_array(
-                store=store,
-                shape=(1,),
-                dtype=dtype,
-                zarr_format=3,
-                serializer=none_serializer,
-            )
-
 
 async def test_scalar_array() -> None:
     arr = zarr.array(1.5)

tests/test_codecs/test_endian.py

@@ -11,6 +11,7 @@
 from .test_codecs import _AsyncArrayProxy
 
 
+@pytest.mark.filterwarnings("ignore:The endianness of the requested serializer")
 @pytest.mark.parametrize("store", ["local", "memory"], indirect=["store"])
 @pytest.mark.parametrize("endian", ["big", "little"])
 async def test_endian(store: Store, endian: Literal["big", "little"]) -> None:
@@ -32,6 +33,7 @@ async def test_endian(store: Store, endian: Literal["big", "little"]) -> None:
     assert np.array_equal(data, readback_data)
 
 
+@pytest.mark.filterwarnings("ignore:The endianness of the requested serializer")
 @pytest.mark.parametrize("store", ["local", "memory"], indirect=["store"])
 @pytest.mark.parametrize("dtype_input_endian", [">u2", "<u2"])
 @pytest.mark.parametrize("dtype_store_endian", ["big", "little"])