fix(series): #1372 🧱✖️ cumprod (#1374)

fix(series): #1372 cumprod

Author: cmp0xff

pandas-stubs/core/series.pyi

@@ -210,6 +210,10 @@ from pandas.plotting import PlotAccessor
 class _SupportsAdd(Protocol[_T_co]):
     def __add__(self, value: Self, /) -> _T_co: ...
 
+@type_check_only
+class _SupportsMul(Protocol[_T_co]):
+    def __mul__(self, value: Self, /) -> _T_co: ...
+
 class _iLocIndexerSeries(_iLocIndexer, Generic[S1]):
     # get item
     @overload
@@ -3821,23 +3825,23 @@ class Series(IndexOpsMixin[S1], NDFrame):
     ) -> Series[S1]: ...
     @overload
     def cumprod(
-        self: Series[_str],
+        self: Series[Never],
         axis: AxisIndex = ...,
         skipna: _bool = ...,
         *args: Any,
         **kwargs: Any,
-    ) -> Never: ...
+    ) -> Series: ...
     @overload
     def cumprod(
-        self: Series[Timestamp],
+        self: Series[bool],
         axis: AxisIndex = ...,
         skipna: _bool = ...,
         *args: Any,
         **kwargs: Any,
-    ) -> Never: ...
+    ) -> Series[int]: ...
     @overload
     def cumprod(
-        self,
+        self: SupportsGetItem[Scalar, _SupportsMul[S1]],
         axis: AxisIndex = ...,
         skipna: _bool = ...,
         *args: Any,
@@ -4369,39 +4373,18 @@ class TimedeltaSeries(_SeriesSubclassBase[Timedelta, np.timedelta64]):
         *args: Any,
         **kwargs: Any,
     ) -> TimedeltaSeries: ...
-    def cumprod(  # pyrefly: ignore
-        self,
-        axis: AxisIndex = ...,
-        skipna: _bool = ...,
-        *args: Any,
-        **kwargs: Any,
-    ) -> Never: ...
 
 class PeriodSeries(_SeriesSubclassBase[Period, np.object_]):
     @property
     def dt(self) -> PeriodProperties: ...  # type: ignore[override] # pyright: ignore[reportIncompatibleMethodOverride]
     def __sub__(self, other: PeriodSeries) -> OffsetSeries: ...  # type: ignore[override] # pyright: ignore[reportIncompatibleMethodOverride]
     def diff(self, periods: int = ...) -> OffsetSeries: ...  # type: ignore[override] # pyright: ignore[reportIncompatibleMethodOverride]
-    def cumprod(
-        self,
-        axis: AxisIndex = ...,
-        skipna: _bool = ...,
-        *args: Any,
-        **kwargs: Any,
-    ) -> Never: ...
 
 class OffsetSeries(_SeriesSubclassBase[BaseOffset, np.object_]):
     @overload  # type: ignore[override]
     def __radd__(self, other: Period) -> PeriodSeries: ...
     @overload
     def __radd__(self, other: BaseOffset) -> OffsetSeries: ...
-    def cumprod(  # pyrefly: ignore
-        self,
-        axis: AxisIndex = ...,
-        skipna: _bool = ...,
-        *args: Any,
-        **kwargs: Any,
-    ) -> Never: ...
 
 class IntervalSeries(
     _SeriesSubclassBase[Interval[_OrderableT], np.object_], Generic[_OrderableT]

tests/series/test_cumul.py

@@ -0,0 +1,51 @@
+import numpy as np
+import pandas as pd
+from typing_extensions import assert_type
+
+from tests import (
+    TYPE_CHECKING_INVALID_USAGE,
+    check,
+)
+
+
+def test_cumul_any_float() -> None:
+    series = pd.DataFrame({"A": [1.0, float("nan"), 2.0]})["A"]
+    check(assert_type(series.cumprod(), pd.Series), pd.Series, np.floating)
+
+
+def test_cumul_bool() -> None:
+    series = pd.Series([True, False, True])
+    check(assert_type(series.cumprod(), "pd.Series[int]"), pd.Series, np.integer)
+
+
+def test_cumul_int() -> None:
+    series = pd.Series([3, 1, 2])
+    check(assert_type(series.cumprod(), "pd.Series[int]"), pd.Series, np.integer)
+
+
+def test_cumul_float() -> None:
+    series = pd.Series([3.0, float("nan"), 2.0])
+    check(assert_type(series.cumprod(), "pd.Series[float]"), pd.Series, np.floating)
+
+
+def test_cumul_complex() -> None:
+    series = pd.Series([3j, 3 + 4j, 2j])
+    check(
+        assert_type(series.cumprod(), "pd.Series[complex]"),
+        pd.Series,
+        np.complexfloating,
+    )
+
+
+def test_cumul_str() -> None:
+    series = pd.Series(["1", "a", "🐼"])
+    if TYPE_CHECKING_INVALID_USAGE:
+        series.cumprod()  # type: ignore[misc] # pyright: ignore[reportAttributeAccessIssue]
+
+
+def test_cumul_ts() -> None:
+    series = pd.Series(pd.to_datetime(["2025-09-18", "2025-09-18", "2025-09-18"]))
+    check(assert_type(series, "pd.Series[pd.Timestamp]"), pd.Series, pd.Timestamp)
+
+    if TYPE_CHECKING_INVALID_USAGE:
+        series.cumprod()  # type: ignore[misc] # pyright: ignore[reportAttributeAccessIssue]

tests/series/test_series.py

@@ -3946,24 +3946,18 @@ def test_timedelta_index_cumprod() -> None:
     offset_series = as_period_series - as_period_series
 
     if TYPE_CHECKING_INVALID_USAGE:
-        assert_type(pd.Series(["a", "b"]).cumprod(), Never)
+        offset_series.cumprod()  # type: ignore[misc] # pyright: ignore[reportAttributeAccessIssue]
 
     if TYPE_CHECKING_INVALID_USAGE:
-        assert_type(offset_series.cumprod(), Never)
+        pd.Series([pd.Timedelta(0), pd.Timedelta(1)]).cumprod()  # type: ignore[misc] # pyright: ignore[reportAttributeAccessIssue]
 
     if TYPE_CHECKING_INVALID_USAGE:
-        assert_type(pd.Series([pd.Timedelta(0), pd.Timedelta(1)]).cumprod(), Never)
+        pd.Series(  # type: ignore[misc]
+            [pd.Timestamp("2024-04-29"), pd.Timestamp("2034-08-28")]
+        ).cumprod()  # pyright: ignore[reportAttributeAccessIssue]
 
     if TYPE_CHECKING_INVALID_USAGE:
-        assert_type(
-            pd.Series(
-                [pd.Timestamp("2024-04-29"), pd.Timestamp("2034-08-28")]
-            ).cumprod(),
-            Never,
-        )
-
-    if TYPE_CHECKING_INVALID_USAGE:
-        assert_type(as_period_series.cumprod(), Never)
+        as_period_series.cumprod()  # type: ignore[misc] # pyright: ignore[reportAttributeAccessIssue]
 
 
 def test_series_str_methods() -> None: