ENH: support downcasting of nullable EAs in pd.to_numeric

pandas/core/tools/numeric.py

@@ -198,18 +198,17 @@ def to_numeric(arg, errors="raise", downcast=None):
                         break
 
     if mask is not None:
-        buf = np.zeros(mask.shape, dtype=values.dtype)
-        buf[~mask] = values
-        values = buf
+        data = np.zeros(mask.shape, dtype=values.dtype)
+        data[~mask] = values
 
-        if is_integer_dtype(values):
+        if is_integer_dtype(data):
             from pandas.core.arrays import IntegerArray
 
-            values = IntegerArray(values, mask)
-        elif is_float_dtype(values):
+            values = IntegerArray(data, mask)
+        elif is_float_dtype(data):
             from pandas.core.arrays import FloatingArray
 
-            values = FloatingArray(values, mask)
+            values = FloatingArray(data, mask)
 
     if is_series:
         return arg._constructor(values, index=arg.index, name=arg.name)

pandas/tests/tools/test_to_numeric.py

@@ -731,17 +731,23 @@ def test_to_numeric_from_nullable_string(values, expected):
     "data, input_dtype, downcast, expected_dtype",
     (
         ([1, 1], "Int64", "integer", "Int8"),
+        ([1.0, 1.0], "Float64", "integer", "Int8"),
+        ([1.0, 1.1], "Float64", "integer", "Float64"),
         ([1, pd.NA], "Int64", "integer", "Int8"),
         ([450, 300], "Int64", "integer", "Int16"),
         ([1, 1], "Int64", "signed", "Int8"),
+        ([1.0, 1.0], "Float32", "signed", "Int8"),
+        ([1.0, 1.1], "Float64", "signed", "Float64"),
         ([1, pd.NA], "Int64", "signed", "Int8"),
         ([450, -300], "Int64", "signed", "Int16"),
         ([1, 1], "Int64", "unsigned", "UInt8"),
+        ([1.0, 1.0], "Float32", "unsigned", "UInt8"),
+        ([1.0, 1.1], "Float64", "unsigned", "Float64"),
         ([1, pd.NA], "Int64", "unsigned", "UInt8"),
         ([450, -300], "Int64", "unsigned", "Int64"),
         ([-1, -1], "Int32", "unsigned", "Int32"),
         ([1, 1], "Float64", "float", "Float32"),
-        ([1, 1], "Float64", "float", "Float32"),
+        ([1, 1.1], "Float64", "float", "Float32"),
         ([1, 1], "Float64", "integer", "Int8"),
     ),
 )