fix(dtype): accept platform-equivalent numpy dtypes in from_native_dtype

src/zarr/core/dtype/wrapper.py

@@ -84,7 +84,27 @@ def _check_native_dtype(cls: type[Self], dtype: TBaseDType) -> TypeGuard[DType]:
         Bool
             True if the dtype matches, False otherwise.
         """
-        return type(dtype) is cls.dtype_cls
+        # Keep the exact class check in a variable: narrowing on ``type(dtype) is ...``
+        # makes mypy treat the layout fallback below as unreachable.
+        exact_match = type(dtype) is cls.dtype_cls
+        if exact_match:
+            return True
+        # NumPy's C type spellings do not always map to the canonical dtype class:
+        # ``np.dtype("q")`` is a ``LongLongDType`` instance rather than an
+        # ``Int64DType`` instance, even though the two describe the same memory
+        # layout. The width of ``long long`` depends on the platform NumPy was
+        # built for, so the dtype class alone is not a reliable test. Fall back to
+        # comparing the layout (kind and item size), which is what a Zarr data type
+        # actually encodes.
+        try:
+            # numpy's stubs only type ``dtype(...)`` with an argument; the concrete
+            # dtype classes (``np.dtypes.Int64DType`` etc.) construct without one.
+            expected: TBaseDType = cls.dtype_cls()  # type: ignore[call-overload]
+        except TypeError:
+            # Flexible/parametric dtypes (e.g. ``VoidDType``) have no fixed layout
+            # to compare against, so the exact dtype class check above stands.
+            return False
+        return bool(dtype.kind == expected.kind and dtype.itemsize == expected.itemsize)
 
     @classmethod
     @abstractmethod

tests/test_dtype/test_npy/test_int.py

@@ -117,7 +117,10 @@ class TestInt32(BaseTestZDType):
 class TestInt64(BaseTestZDType):
     test_cls = Int64
     scalar_type = np.int64
-    valid_dtype = (np.dtype(">i8"), np.dtype("<i8"))
+    # np.dtype("q") is a np.dtypes.LongLongDType instance, not a np.dtypes.Int64DType
+    # instance, even though "long long" is 64-bit on this platform. It describes the
+    # same layout, so it is a valid Int64. See issue #3282.
+    valid_dtype = (np.dtype(">i8"), np.dtype("<i8"), np.dtype("q"))
     invalid_dtype = (
         np.dtype(np.int8),
         np.dtype(np.uint16),
@@ -267,7 +270,11 @@ class TestUInt32(BaseTestZDType):
 class TestUInt64(BaseTestZDType):
     test_cls = UInt64
     scalar_type = np.uint64
-    valid_dtype = (np.dtype(">u8"), np.dtype("<u8"))
+    # np.dtype("Q") is a np.dtypes.ULongLongDType instance, not a
+    # np.dtypes.UInt64DType instance, even though "unsigned long long" is 64-bit on
+    # this platform. It describes the same layout, so it is a valid UInt64.
+    # See issue #3282.
+    valid_dtype = (np.dtype(">u8"), np.dtype("<u8"), np.dtype("Q"))
     invalid_dtype = (
         np.dtype(np.int8),
         np.dtype(np.int16),

tests/test_dtype_registry.py

@@ -20,9 +20,11 @@
     FixedLengthUTF32,
     Int8,
     Int16,
+    Int64,
     RawBytes,
     Struct,
     UInt8,
+    UInt64,
     VariableLengthUTF8,
     ZDType,
     data_type_registry,
@@ -91,6 +93,22 @@ def test_match_dtype_string_na_object_error(
         with pytest.raises(ValueError, match=r"Zarr data type resolution from StringDType.*failed"):
             data_type_registry_fixture.match_dtype(dtype)
 
+    @staticmethod
+    @pytest.mark.parametrize(("dtype_str", "expected_cls"), [("q", Int64), ("Q", UInt64)])
+    def test_match_dtype_c_type_spelling(dtype_str: str, expected_cls: type) -> None:
+        """
+        Test that the C type-name spellings resolve through the registry.
+
+        ``np.dtype("q")`` and ``np.dtype("Q")`` are ``LongLongDType`` and
+        ``ULongLongDType`` instances rather than ``Int64DType`` and ``UInt64DType``
+        instances, even though on this platform they describe the same layout. They
+        must still resolve to exactly one data type. See issue #3282.
+        """
+        dtype = np.dtype(dtype_str)
+        assert isinstance(data_type_registry.match_dtype(dtype), expected_cls)
+        for zarr_format in (2, 3):
+            assert isinstance(parse_dtype(dtype, zarr_format=zarr_format), expected_cls)
+
     @staticmethod
     def test_unregistered_dtype(data_type_registry_fixture: DataTypeRegistry) -> None:
         """