Fix

Author: dcherian

flox/core.py

@@ -2425,6 +2425,9 @@ def groupby_reduce(
     if method == "cohorts" and any_by_dask:
         raise ValueError(f"method={method!r} can only be used when grouping by numpy arrays.")
 
+    if not is_duck_array(array):
+        array = np.asarray(array)
+
     reindex = _validate_reindex(
         reindex,
         func,
@@ -2435,8 +2438,6 @@ def groupby_reduce(
         array.dtype,
     )
 
-    if not is_duck_array(array):
-        array = np.asarray(array)
     is_bool_array = np.issubdtype(array.dtype, bool)
     array = array.astype(np.intp) if is_bool_array else array
 

tests/test_core.py

@@ -1590,18 +1590,36 @@ def test_validate_reindex_map_reduce(
     dask_expected, reindex, func, expected_groups, any_by_dask
 ) -> None:
     actual = _validate_reindex(
-        reindex, func, "map-reduce", expected_groups, any_by_dask, is_dask_array=True
+        reindex,
+        func,
+        "map-reduce",
+        expected_groups,
+        any_by_dask,
+        is_dask_array=True,
+        array_dtype=np.dtype("int32"),
     )
     assert actual is dask_expected
 
     # always reindex with all numpy inputs
     actual = _validate_reindex(
-        reindex, func, "map-reduce", expected_groups, any_by_dask=False, is_dask_array=False
+        reindex,
+        func,
+        "map-reduce",
+        expected_groups,
+        any_by_dask=False,
+        is_dask_array=False,
+        array_dtype=np.dtype("int32"),
     )
     assert actual
 
     actual = _validate_reindex(
-        True, func, "map-reduce", expected_groups, any_by_dask=False, is_dask_array=False
+        True,
+        func,
+        "map-reduce",
+        expected_groups,
+        any_by_dask=False,
+        is_dask_array=False,
+        array_dtype=np.dtype("int32"),
     )
     assert actual
 
@@ -1611,19 +1629,37 @@ def test_validate_reindex() -> None:
     for method in methods:
         with pytest.raises(NotImplementedError):
             _validate_reindex(
-                True, "argmax", method, expected_groups=None, any_by_dask=False, is_dask_array=True
+                True,
+                "argmax",
+                method,
+                expected_groups=None,
+                any_by_dask=False,
+                is_dask_array=True,
+                array_dtype=np.dtype("int32"),
             )
 
     methods: list[T_Method] = ["blockwise", "cohorts"]
     for method in methods:
         with pytest.raises(ValueError):
             _validate_reindex(
-                True, "sum", method, expected_groups=None, any_by_dask=False, is_dask_array=True
+                True,
+                "sum",
+                method,
+                expected_groups=None,
+                any_by_dask=False,
+                is_dask_array=True,
+                array_dtype=np.dtype("int32"),
             )
 
         for func in ["sum", "argmax"]:
             actual = _validate_reindex(
-                None, func, method, expected_groups=None, any_by_dask=False, is_dask_array=True
+                None,
+                func,
+                method,
+                expected_groups=None,
+                any_by_dask=False,
+                is_dask_array=True,
+                array_dtype=np.dtype("int32"),
             )
             assert actual is False
 
@@ -1635,6 +1671,7 @@ def test_validate_reindex() -> None:
             expected_groups=np.array([1, 2, 3]),
             any_by_dask=False,
             is_dask_array=True,
+            array_dtype=np.dtype("int32"),
         )
 
     assert _validate_reindex(
@@ -1644,6 +1681,7 @@ def test_validate_reindex() -> None:
         expected_groups=np.array([1, 2, 3]),
         any_by_dask=True,
         is_dask_array=True,
+        array_dtype=np.dtype("int32"),
     )
     assert _validate_reindex(
         None,
@@ -1652,8 +1690,24 @@ def test_validate_reindex() -> None:
         expected_groups=np.array([1, 2, 3]),
         any_by_dask=True,
         is_dask_array=True,
+        array_dtype=np.dtype("int32"),
     )
 
+    kwargs = dict(
+        method="blockwise",
+        expected_groups=np.array([1, 2, 3]),
+        any_by_dask=True,
+        is_dask_array=True,
+    )
+
+    for func in ["nanfirst", "nanlast"]:
+        assert not _validate_reindex(None, func, array_dtype=np.dtype("int32"), **kwargs)  # type: ignore
+        assert _validate_reindex(None, func, array_dtype=np.dtype("float32"), **kwargs)  # type: ignore
+
+    for func in ["first", "last"]:
+        assert not _validate_reindex(None, func, array_dtype=np.dtype("int32"), **kwargs)  # type: ignore
+        assert not _validate_reindex(None, func, array_dtype=np.dtype("float32"), **kwargs)  # type: ignore
+
 
 @requires_dask
 def test_1d_blockwise_sort_optimization():