GH1541 Revert Series[Any].__add__(str) (#1542)

* GH1541 Revert Series[Any].__add__(str)

* GH1541 Revert Series[Any].__add__(str)

* GH1541 PR Feedback

* GH1541 PR Feedback

* GH1541 PR Feedback

* GH1541 PR Feedback

* GH1541 PR Feedback

* GH1541 PR Feedback

Author: loicdiridollou

pandas-stubs/core/indexes/base.pyi

@@ -626,7 +626,7 @@ class Index(IndexOpsMixin[S1], ElementOpsMixin[S1]):
     def __lt__(self, other: Self | S1) -> np_1darray_bool: ...  # type: ignore[override] # pyright: ignore[reportIncompatibleMethodOverride]
     def __gt__(self, other: Self | S1) -> np_1darray_bool: ...  # type: ignore[override] # pyright: ignore[reportIncompatibleMethodOverride]
     @overload
-    def __add__(self: Index[Never], other: _str) -> Never: ...
+    def __add__(self: Index[Never], other: _str) -> Index[_str]: ...
     @overload
     def __add__(
         self: Index[Never], other: complex | ArrayLike | SequenceNotStr[S1] | Index
@@ -680,7 +680,7 @@ class Index(IndexOpsMixin[S1], ElementOpsMixin[S1]):
         self: Index[_str], other: np_ndarray_str | Index[_str]
     ) -> Index[_str]: ...
     @overload
-    def __radd__(self: Index[Never], other: _str) -> Never: ...
+    def __radd__(self: Index[Never], other: _str) -> Index[_str]: ...
     @overload
     def __radd__(
         self: Index[Never], other: complex | ArrayLike | SequenceNotStr[S1] | Index

pandas-stubs/core/series.pyi

@@ -1789,6 +1789,8 @@ class Series(IndexOpsMixin[S1], ElementOpsMixin[S1], NDFrame):
     # just failed to generate these so I couldn't match
     # them up.
     @overload
+    def __add__(self: Series[Never], other: _str) -> Series[_str]: ...
+    @overload
     def __add__(self: Series[Never], other: complex | ListLike) -> Series: ...
     @overload
     def __add__(self, other: Index[Never] | Series[Never]) -> Series: ...
@@ -1875,6 +1877,14 @@ class Series(IndexOpsMixin[S1], ElementOpsMixin[S1], NDFrame):
         self: Series[_str], other: np_ndarray_str | Index[_str] | Series[_str]
     ) -> Series[_str]: ...
     @overload
+    def add(
+        self: Series[Never],
+        other: _str,
+        level: Level | None = None,
+        fill_value: float | None = None,
+        axis: int = 0,
+    ) -> Series[_str]: ...
+    @overload
     def add(
         self: Series[Never],
         other: complex | ListLike,
@@ -2008,6 +2018,8 @@ class Series(IndexOpsMixin[S1], ElementOpsMixin[S1], NDFrame):
         axis: int = 0,
     ) -> Series[_str]: ...
     @overload
+    def __radd__(self: Series[Never], other: _str) -> Series[_str]: ...
+    @overload
     def __radd__(self: Series[Never], other: complex | ListLike) -> Series: ...
     @overload
     def __radd__(self, other: Index[Never] | Series[Never]) -> Series: ...
@@ -2108,6 +2120,14 @@ class Series(IndexOpsMixin[S1], ElementOpsMixin[S1], NDFrame):
     @overload
     def __radd__(self: Series[BaseOffset], other: BaseOffset) -> Series[BaseOffset]: ...
     @overload
+    def radd(
+        self: Series[Never],
+        other: _str,
+        level: Level | None = None,
+        fill_value: float | None = None,
+        axis: int = 0,
+    ) -> Series[_str]: ...
+    @overload
     def radd(
         self: Series[Never],
         other: complex | ListLike,

tests/indexes/arithmetic/test_add.py

@@ -2,10 +2,7 @@
 
 import numpy as np
 import pandas as pd
-from typing_extensions import (
-    Never,
-    assert_type,
-)
+from typing_extensions import assert_type
 
 from tests import (
     TYPE_CHECKING_INVALID_USAGE,
@@ -105,7 +102,13 @@ def test_add_i_pd_index() -> None:
 def test_add_i_py_str() -> None:
     """Test pd.Index[Any] (int) + Python str"""
     s = "abc"
+    midx = pd.MultiIndex.from_tuples([("a",)])
+    idx = midx.levels[0]
+
+    check(assert_type(idx + "c1", "pd.Index[str]"), pd.Index, str)
+    check(assert_type("c1" + idx, "pd.Index[str]"), pd.Index, str)
 
     if TYPE_CHECKING_INVALID_USAGE:
-        assert_type(left_i + s, Never)
-        assert_type(s + left_i, Never)
+        # GH1541 relaxing typing, won't work at runtime though
+        assert_type(left_i + s, "pd.Index[str]")
+        assert_type(s + left_i, "pd.Index[str]")

tests/series/arithmetic/test_add.py

@@ -181,3 +181,14 @@ def test_add_i_pd_series() -> None:
     check(assert_type(left_i.radd(i), pd.Series), pd.Series)
     check(assert_type(left_i.radd(f), pd.Series), pd.Series)
     check(assert_type(left_i.radd(c), pd.Series), pd.Series)
+
+
+def test_series_add_str() -> None:
+    """Test Series.__add__ with Series[Any]."""
+    df = pd.DataFrame({0: ["a", "b"]})
+    sr = df[0]
+
+    check(assert_type(sr + "c1", "pd.Series[str]"), pd.Series, str)
+    check(assert_type("c1" + sr, "pd.Series[str]"), pd.Series, str)
+    check(assert_type(sr.add("c1"), "pd.Series[str]"), pd.Series, str)
+    check(assert_type(sr.radd("c1"), "pd.Series[str]"), pd.Series, str)