type to_offset (#1113)

Author: MarcoGorelli

pandas-stubs/_libs/tslibs/offsets.pyi

@@ -103,11 +103,6 @@ class BaseOffset:
 class SingleConstructorOffset(BaseOffset):
     def __reduce__(self): ...
 
-@overload
-def to_offset(freq: None) -> None: ...
-@overload
-def to_offset(freq: timedelta | BaseOffset | str) -> BaseOffset: ...
-
 class Tick(SingleConstructorOffset):
     def __init__(self, n: int = ..., normalize: bool = ...) -> None: ...
     @property

pandas-stubs/tseries/frequencies.pyi

@@ -1,12 +1,19 @@
+from typing import overload
+
 from pandas import (
     DatetimeIndex,
     Series,
     TimedeltaIndex,
 )
 
-from pandas.tseries.offsets import DateOffset as DateOffset
+from pandas._typing import Frequency
+
+from pandas.tseries.offsets import DateOffset
 
 def get_period_alias(offset_str: str) -> str | None: ...
-def to_offset(freq) -> DateOffset | None: ...
+@overload
+def to_offset(freq: None) -> None: ...
+@overload
+def to_offset(freq: Frequency) -> DateOffset: ...
 def get_offset(name: str) -> DateOffset: ...
 def infer_freq(index: Series | DatetimeIndex | TimedeltaIndex) -> str | None: ...

tests/test_timefuncs.py

@@ -28,7 +28,9 @@
 
 from pandas._libs import NaTType
 from pandas._libs.tslibs import BaseOffset
-from pandas._libs.tslibs.offsets import DateOffset
+
+from pandas.tseries.frequencies import to_offset
+from pandas.tseries.offsets import DateOffset
 
 if TYPE_CHECKING:
     from pandas._typing import FulldatetimeDict
@@ -1425,3 +1427,8 @@ def test_DatetimeIndex_sub_timedelta() -> None:
         ),
         pd.DatetimeIndex,
     )
+
+
+def test_to_offset() -> None:
+    check(assert_type(to_offset(None), None), type(None))
+    check(assert_type(to_offset("1D"), DateOffset), DateOffset)