don't accept, only raise with more informative exception

doc/source/whatsnew/v3.0.0.rst

@@ -280,7 +280,6 @@ Performance improvements
 
 Bug fixes
 ~~~~~~~~~
-- Fixed bug in :class:`Series.Holiday` that leads to a ``TypeError`` when using ``Holiday.dates`` with a ``Holiday`` that is initialized with ``offset`` of type ``list`` which itself references another Holiday's list of offsets. (:issue:`29049`)
 - Fixed bug in :class:`SparseDtype` for equal comparison with na fill value. (:issue:`54770`)
 - Fixed bug in :meth:`DataFrame.join` inconsistently setting result index name (:issue:`55815`)
 - Fixed bug in :meth:`DataFrame.to_string` that raised ``StopIteration`` with nested DataFrames. (:issue:`16098`)

pandas/tests/tseries/holiday/test_holiday.py

@@ -6,7 +6,6 @@
 from pandas import (
  DatetimeIndex,
  Series,
- to_datetime,
 )
 import pandas._testing as tm
 
@@ -199,33 +198,6 @@ def test_holidays_within_dates(holiday, start, expected):
  ) == [utc.localize(dt) for dt in expected]
 
 
-def test_holidays_within_dates_offset_of_offset():
- # see gh-29049
- # Test that the offset of an offset is correctly applied to the holiday
- # And that dates can be calculated
- holiday1 = Holiday(
- "Holiday1",
- month=USThanksgivingDay.month,
- day=USThanksgivingDay.day,
- offset=[USThanksgivingDay.offset, DateOffset(1)],
- )
- holiday2 = Holiday(
- "Holiday2",
- month=holiday1.month,
- day=holiday1.day,
- offset=[holiday1.offset, DateOffset(3)],
- )
- # there shall be no lists of lists here
- for offset in holiday2.offset:
- assert isinstance(offset, DateOffset)
-
- min_date, max_date = (to_datetime(x) for x in ["2017-11-1", "2018-11-30"])
- expected_min, expected_max = DatetimeIndex(["2017-11-27", "2018-11-26"])
- actual_min, actual_max = holiday2.dates(min_date, max_date)
- assert actual_min == expected_min
- assert actual_max == expected_max
-
-
 @pytest.mark.parametrize(
  "transform", [lambda x: x.strftime("%Y-%m-%d"), lambda x: Timestamp(x)]
 )
@@ -299,6 +271,24 @@ def test_both_offset_observance_raises():
  )
 
 
+def test_list_of_list_of_offsets_raises():
+ # see gh-29049
+ # Test that the offsets of offsets are forbidden
+ holiday1 = Holiday(
+ "Holiday1",
+ month=USThanksgivingDay.month,
+ day=USThanksgivingDay.day,
+ offset=[USThanksgivingDay.offset, DateOffset(1)],
+ )
+ with pytest.raises(ValueError, match="Nested lists are not supported for offset"):
+ Holiday(
+ "Holiday2",
+ month=holiday1.month,
+ day=holiday1.day,
+ offset=[holiday1.offset, DateOffset(3)],
+ )
+
+
 def test_half_open_interval_with_observance():
  # Prompted by GH 49075
  # Check for holidays that have a half-open date interval where

pandas/tseries/holiday.py

@@ -166,7 +166,7 @@ def __init__(
  year=None,
  month=None,
  day=None,
- offset: BaseOffset | list[BaseOffset | list[BaseOffset]] | None = None,
+ offset: BaseOffset | list[BaseOffset] | None = None,
  observance: Callable | None = None,
  start_date=None,
  end_date=None,
@@ -235,22 +235,17 @@ class from pandas.tseries.offsets, default None
  """
  if offset is not None and observance is not None:
  raise NotImplementedError("Cannot use both offset and observance.")
+ if isinstance(offset, list) and any(isinstance(off, list) for off in offset):
+ raise ValueError(
+ "Nested lists are not supported for offset. "
+ "Flatten composite offsets of `Holiday.offset`s first."
+ )
 
  self.name = name
  self.year = year
  self.month = month
  self.day = day
- self.offset: None | BaseOffset | list[BaseOffset]
- if isinstance(offset, list):
- self.offset = []
- for off in offset:
- # check if we are handling composite offsets of another holiday
- if isinstance(off, list):
- self.offset.extend(off)
- else:
- self.offset.append(off)
- else:
- self.offset = offset
+ self.offset = offset
  self.start_date = (
  Timestamp(start_date) if start_date is not None else start_date
  )