BUG: 'Series.to_numpy(dtype=, na_value=)' behaves differently with 'pd.NA' and 'np.nan'

Author: MarcoGorelli

doc/source/whatsnew/v1.6.0.rst

@@ -216,6 +216,7 @@ Indexing
 Missing
 ^^^^^^^
 - Bug in :meth:`Index.equals` raising ``TypeError`` when :class:`Index` consists of tuples that contain ``NA`` (:issue:`48446`)
+- Bug when calling :meth:`Series.to_numpy` on a Series of ``object`` dtype containing ``pd.NA`` was raising even if ``na_value`` was valid (:issue:`48951`)
 -
 
 MultiIndex

pandas/core/base.py

@@ -537,12 +537,14 @@ def to_numpy(
                 f"to_numpy() got an unexpected keyword argument '{bad_keys}'"
             )
 
-        result = np.asarray(self._values, dtype=dtype)
         # TODO(GH-24345): Avoid potential double copy
         if copy or na_value is not lib.no_default:
-            result = result.copy()
+            result = self._values.copy()
             if na_value is not lib.no_default:
                 result[np.asanyarray(self.isna())] = na_value
+            result = np.asarray(result, dtype=dtype)
+        else:
+            result = np.asarray(self._values, dtype=dtype)
         return result
 
     @property

pandas/tests/base/test_conversion.py

@@ -398,6 +398,7 @@ def test_to_numpy_dtype(as_series):
     "values, dtype, na_value, expected",
     [
         ([1, 2, None], "float64", 0, [1.0, 2.0, 0.0]),
+        ([1, 2, pd.NA, 4], "int32", 0, [1, 2, 0, 4]),
         (
             [Timestamp("2000"), Timestamp("2000"), pd.NaT],
             None,
@@ -411,7 +412,7 @@ def test_to_numpy_na_value_numpy_dtype(
 ):
     obj = index_or_series(values)
     result = obj.to_numpy(dtype=dtype, na_value=na_value)
-    expected = np.array(expected)
+    expected = np.array(expected, dtype=dtype)
     tm.assert_numpy_array_equal(result, expected)