test(cast_value): cover cast_value next to the transpose codec

Regression test for zarr-developers#4237: a cast_value codec on either side of a
transpose codec must round-trip, because transpose hands the next codec
a non-row-major view.

Imported unchanged from zarr-developers#4238, where this test was written. The
np.ascontiguousarray workaround that accompanied it there is
deliberately left out: cast-value-rs 0.4.2 normalizes layout itself, and
the workaround promotes 0-d arrays to shape (1,), breaking 0-d arrays.

Co-authored-by: Raphael Jolivet <raphael.jolivet@minesparis.psl.eu>
Assisted-by: ClaudeCode:claude-fable-5

Author: raphaeljolivet

tests/test_codecs/test_cast_value.py

@@ -4,10 +4,13 @@
 
 import numpy as np
 import pytest
+from numpy.testing import assert_array_equal
 
 import zarr
 from tests.conftest import Expect, ExpectFail
+from zarr.codecs import BytesCodec, TransposeCodec
 from zarr.codecs.cast_value import CastValue
+from zarr.storage import MemoryStore
 
 try:
     import cast_value_rs  # noqa: F401
@@ -561,3 +564,50 @@ def test_min_version_matches_pyproject() -> None:
     match = re.fullmatch(r"cast-value-rs>=(?P<version>[\w.]+)", requirement)
     assert match is not None, f"unexpected requirement form: {requirement!r}"
     assert match.group("version") == CAST_VALUE_RS_MIN_VERSION
+
+
+# ---------------------------------------------------------------------------
+# Non-contiguous input (regression for #4237)
+# ---------------------------------------------------------------------------
+
+
+@requires_cast_value_rs
+def test_enforce_contiguous_arrays() -> None:
+    """
+    Transpose codec produces non-contiguous arrays.
+    Ensure cast_value makes them contiguous before processing.
+    """
+    data = np.arange(20, dtype=np.float32).reshape(5, 2, 2)
+
+    def make_array(filters: list[Any]) -> Any:
+        return zarr.create_array(
+            store=MemoryStore(),
+            shape=data.shape,
+            dtype=data.dtype,
+            chunks=data.shape,
+            filters=filters,
+            serializer=BytesCodec(endian="little"),
+            compressors=None,
+            zarr_format=3,
+        )
+
+    # Cast before transpose
+    array = make_array(
+        [
+            CastValue(data_type="uint16"),
+            TransposeCodec(order=(1, 2, 0)),
+        ]
+    )
+    array[:] = data
+    assert_array_equal(array[:], data)
+
+    # Cast after transpose
+    array = make_array(
+        [
+            TransposeCodec(order=(1, 2, 0)),
+            CastValue(data_type="uint16"),
+        ]
+    )
+
+    array[:] = data
+    assert_array_equal(array[:], data)