stopped numeric_only=True from dropping columns

pandas/core/groupby/groupby.py

@@ -1610,8 +1610,6 @@ def _cython_agg_general(
                 raise NotImplementedError(
                     f"{type(self).__name__}.{how} does not implement {kwd_name}."
                 )
-            elif not is_ser:
-                data = data.get_numeric_data(copy=False)
 
         def array_func(values: ArrayLike) -> ArrayLike:
             try:

pandas/tests/groupby/test_groupby.py

@@ -2694,3 +2694,62 @@ def test_by_column_values_with_same_starting_value():
     ).set_index("Name")
 
     tm.assert_frame_equal(result, expected_result)
+
+
+@pytest.mark.parametrize(
+    "columns, index, numeric_only",
+    [   # the only element changed between tests is numeric_only, but all are parameterized
+        pytest.param(
+            ['a', 'b'],
+            ['a'],
+            False,
+        ),
+        pytest.param(
+            ['a', 'b'],
+            ['a'],
+            None,
+        ),
+        pytest.param(
+            ['a', 'b'],
+            ['a'],
+            True,
+        ),
+    ],
+)
+def test_empty_frame_groupby_numeric_only(columns, index, numeric_only):
+    # GH 46375 - certain values of numeric_only are causing the df to drop columns
+    df = pd.DataFrame(columns=columns)
+    expected = pd.DataFrame(columns=columns).set_index(index)
+    result = df.groupby(index).first(numeric_only=numeric_only)
+    tm.assert_frame_equal(result, expected)
+
+
+@pytest.mark.parametrize(
+    "data, index, numeric_only, expected_data",
+    [   # the only element changed between tests is numeric_only, but all are parameterized
+        pytest.param(
+            { "a": [0, 0, 1, 1], "b": [1, "x", 2, "y"], "c": [1, 1, 2, 2],},
+            ['a'],
+            False,
+            {"a": [0, 1], "b": [1, 2], "c": [1, 2],}
+        ),
+        pytest.param(
+            { "a": [0, 0, 1, 1], "b": [1, "x", 2, "y"], "c": [1, 1, 2, 2],},
+            ['a'],
+            None,
+            {"a": [0, 1], "b": [1, 2], "c": [1, 2],}
+        ),
+        pytest.param(
+            { "a": [0, 0, 1, 1], "b": [1, "x", 2, "y"], "c": [1, 1, 2, 2],},
+            ['a'],
+            True,
+            {"a": [0, 1], "b": [1, 2], "c": [1, 2],}
+        ),
+    ],
+)
+def test_heterogeneous_frame_groupby_numeric_only(data, index, numeric_only, expected_data):
+    # GH 46375 - certain values of numeric_only are causing the df to drop columns
+    df = pd.DataFrame(data)
+    result = df.groupby(index).first(numeric_only=numeric_only)
+    expected = pd.DataFrame(expected_data).set_index(index)
+    tm.assert_frame_equal(result, expected)