Fix fill_value handling for complex & datetime dtypes

Author: dcherian

src/zarr/core/metadata/v3.py

@@ -257,6 +257,7 @@ def update_attributes(self, attributes: dict[str, JSON]) -> Self:
 FLOAT = np.float16 | np.float32 | np.float64
 COMPLEX_DTYPE = np.dtypes.Complex64DType | np.dtypes.Complex128DType
 COMPLEX = np.complex64 | np.complex128
+DATETIME_DTYPE = np.dtypes.DateTime64DType
 
 
 @overload
@@ -275,6 +276,10 @@ def parse_fill_value(fill_value: object, dtype: FLOAT_DTYPE) -> FLOAT: ...
 def parse_fill_value(fill_value: object, dtype: COMPLEX_DTYPE) -> COMPLEX: ...
 
 
+@overload
+def parse_fill_value(fill_value: object, dtype: DATETIME_DTYPE) -> DATETIME_DTYPE: ...
+
+
 @overload
 def parse_fill_value(fill_value: object, dtype: np.dtype[Any]) -> Any:
     # This dtype[Any] is unfortunately necessary right now.
@@ -314,7 +319,7 @@ def parse_fill_value(
     if fill_value is None:
         return dtype.type(0)
     if isinstance(fill_value, Sequence) and not isinstance(fill_value, str):
-        if dtype in (np.complex64, np.complex128):
+        if dtype.type in (np.complex64, np.complex128):
             dtype = cast(COMPLEX_DTYPE, dtype)
             if len(fill_value) == 2:
                 # complex datatypes serialize to JSON arrays with two elements
@@ -328,7 +333,12 @@ def parse_fill_value(
                 raise ValueError(msg)
         msg = f"Cannot parse non-string sequence {fill_value} as a scalar with type {dtype}."
         raise TypeError(msg)
-    return dtype.type(fill_value)  # type: ignore[arg-type]
+    if np.issubdtype(dtype, np.datetime64):
+        if TYPE_CHECKING:
+            assert isinstance(dtype.type, np.datetime64)
+        return dtype.type(fill_value, np.datetime_data(dtype))  # type: ignore[unreachable]
+    else:
+        return dtype.type(fill_value)  # type: ignore[arg-type]
 
 
 # For type checking

src/zarr/testing/strategies.py

@@ -1,4 +1,3 @@
-import re
 from typing import Any
 
 import hypothesis.extra.numpy as npst
@@ -75,6 +74,7 @@ def arrays(
     path = draw(paths)
     name = draw(array_names)
     attributes = draw(attrs)
+    fill_value = draw(npst.from_dtype(nparray.dtype))
     # compressor = draw(compressors)
 
     # TODO: clean this up
@@ -100,16 +100,6 @@ def arrays(
 
     array_path = path + ("/" if not path.endswith("/") else "") + name
     root = Group.create(store)
-    fill_value_args: tuple[Any, ...] = tuple()
-    if nparray.dtype.kind == "M":
-        m = re.search(r"\[(.+)\]", nparray.dtype.str)
-        if not m:
-            raise ValueError(f"Couldn't find precision for dtype '{nparray.dtype}.")
-
-        fill_value_args = (
-            # e.g. ns, D
-            m.groups()[0],
-        )
 
     a = root.create_array(
         array_path,
@@ -118,7 +108,7 @@ def arrays(
         dtype=nparray.dtype.str,
         attributes=attributes,
         # compressor=compressor,  # TODO: FIXME
-        fill_value=nparray.dtype.type(0, *fill_value_args),
+        fill_value=fill_value,
     )
 
     assert isinstance(a, Array)