Fix of #4237 : 'ValueError: Input array must be contiguous' when *cas…

changes/4238.bugfix.md

@@ -0,0 +1,3 @@
+The codec *cast_value* expects a contiguous numpy array to work properly.
+It used to break when place before or after a *transpose* codec, which produces non-contiguous arrays.
+This fix resolves the issue.

src/zarr/codecs/cast_value.py

@@ -316,8 +316,10 @@ def _do_cast(
             to_src = int if np.issubdtype(src_dtype, np.integer) else float
             to_tgt = int if np.issubdtype(target_dtype, np.integer) else float
             scalar_map_entries = {to_src(k): to_tgt(v) for k, v in scalar_map.items()}
+        # NOTE: the use of np.ascontiguousarray below makes a copy when
+        # the input is not contiguous.
         return cast_array_rs(  # type: ignore[no-any-return]
-            arr,
+            np.ascontiguousarray(arr),
             target_dtype=target_dtype,
             rounding_mode=self.rounding,
             out_of_range_mode=self.out_of_range,

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
@@ -477,3 +480,45 @@ def test_parse_scalar_map(case: Expect[Any, Any]) -> None:
     from zarr.codecs.cast_value import parse_scalar_map
 
     assert parse_scalar_map(case.input) == case.output
+
+
+@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)