Fix an issue in setitem when RangeIndex is present and index does…

…n't exist (#58)

Fixes: #13860

This PR fixes an issue in Series.setitem where if the index is a RangeIndex, we are corrupting the series data & index object by not properly handling RangeIndex separately and not making a copy.

Co-authored-by: Bradley Dice <bdice@bradleydice.com>

python/cudf/cudf/core/series.py

@@ -305,7 +305,28 @@ def __setitem__(self, key, value):
                 and not isinstance(self._frame.index, cudf.MultiIndex)
                 and is_scalar(value)
             ):
-                _append_new_row_inplace(self._frame.index._values, key)
+                # TODO: Modifying index in place is bad because
+                # our index are immutable, but columns are not (which
+                # means our index are mutable with internal APIs).
+                # Get rid of the deep copy once columns too are
+                # immutable.
+                idx_copy = self._frame._index.copy(deep=True)
+                if (
+                    isinstance(idx_copy, cudf.RangeIndex)
+                    and isinstance(key, int)
+                    and (key == idx_copy[-1] + idx_copy.step)
+                ):
+                    idx_copy = cudf.RangeIndex(
+                        start=idx_copy.start,
+                        stop=idx_copy.stop + idx_copy.step,
+                        step=idx_copy.step,
+                        name=idx_copy.name,
+                    )
+                else:
+                    if isinstance(idx_copy, cudf.RangeIndex):
+                        idx_copy = idx_copy._as_int_index()
+                    _append_new_row_inplace(idx_copy._values, key)
+                self._frame._index = idx_copy
                 _append_new_row_inplace(self._frame._column, value)
                 return
             else:

python/cudf/cudf/tests/test_setitem.py

@@ -463,3 +463,44 @@ def test_loc_setitem_series_index_alignment_13031(other_index):
     cs.loc[["1", "3"]] = cother
 
     assert_eq(s, cs)
+
+
+@pytest.mark.parametrize(
+    "ps",
+    [
+        pd.Series([1, 2, 3], index=pd.RangeIndex(0, 3)),
+        pd.Series([1, 2, 3], index=pd.RangeIndex(start=2, stop=-1, step=-1)),
+        pd.Series([1, 2, 3], index=pd.RangeIndex(start=1, stop=6, step=2)),
+        pd.Series(
+            [1, 2, 3, 4, 5], index=pd.RangeIndex(start=1, stop=-9, step=-2)
+        ),
+        pd.Series(
+            [1, 2, 3, 4, 5], index=pd.RangeIndex(start=1, stop=-12, step=-3)
+        ),
+        pd.Series([1, 2, 3, 4], index=pd.RangeIndex(start=1, stop=14, step=4)),
+        pd.Series(
+            [1, 2, 3, 4], index=pd.RangeIndex(start=1, stop=-14, step=-4)
+        ),
+    ],
+)
+@pytest.mark.parametrize("arg", list(range(-20, 20)) + [5.6, 3.1])
+def test_series_set_item_range_index(ps, arg):
+    gsr = cudf.from_pandas(ps)
+    psr = ps.copy(deep=True)
+    psr[arg] = 11
+    gsr[arg] = 11
+
+    assert_eq(psr, gsr, check_index_type=True)
+
+
+def test_series_set_item_index_reference():
+    gs1 = cudf.Series([1], index=[7])
+    gs2 = cudf.Series([2], index=gs1.index)
+    gs1.loc[11] = 2
+
+    ps1 = pd.Series([1], index=[7])
+    ps2 = pd.Series([2], index=ps1.index)
+    ps1.loc[11] = 2
+
+    assert_eq(ps1, gs1)
+    assert_eq(ps2, gs2)