Well, that was subtle.

pandas-dev · mroeschke · Nov 2, 2022 · Oct 15, 2022 · Oct 15, 2022 · Oct 15, 2022
commit 5aca82dcbcf994f814ea7d584900b47d07fa77e2
diff --git a/pandas/tests/tseries/holiday/test_federal.py b/pandas/tests/tseries/holiday/test_federal.py
@@ -1,5 +1,7 @@
 from datetime import datetime
 
+import pandas._testing as tm
+
 from pandas.tseries.holiday import (
     AbstractHolidayCalendar,
     USFederalHolidayCalendar,
@@ -48,4 +50,4 @@ def test_federal_holiday_inconsistent_returntype():
     results_2018 = cal1.holidays(start=datetime(2018, 8, 1), end=datetime(2018, 8, 31))
     results_2019 = cal2.holidays(start=datetime(2019, 8, 1), end=datetime(2019, 8, 31))
 
-    assert type(results_2018) == type(results_2019)
+    tm.assert_index_equal(results_2018, results_2019)
diff --git a/pandas/tests/tseries/holiday/test_holiday.py b/pandas/tests/tseries/holiday/test_holiday.py
@@ -267,7 +267,11 @@ def test_both_offset_observance_raises():
 
 
 def test_half_open_interval_with_observance():
-    # See GH 49075.
+    # Prompted by GH 49075
+    # Given holidays with a half-open date interval and a defined
+    # observance pattern,  we check to make sure that the return type
+    # for Holiday.dates() remains consistent before/after the date that
+    # marks the 'edge' of the half-open date interval
     holiday_1 = Holiday(
         "Arbitrary Holiday - start 2022-03-14",
         start_date=datetime(2022, 3, 14),
@@ -291,17 +295,17 @@ class TestHolidayCalendar(AbstractHolidayCalendar):
             USLaborDay,
         ]
 
-    start_datum = Timestamp("2022-08-01")
-    end_datum = Timestamp("2022-08-31")
+    start = Timestamp("2022-08-01")
+    end = Timestamp("2022-08-31")
     test_cal = TestHolidayCalendar()
 
-    three_years_before = test_cal.holidays(
-        start_datum - DateOffset(years=3), end_datum - DateOffset(years=3)
+    check_before_edge = test_cal.holidays(
+        start - DateOffset(years=3), end - DateOffset(years=3)
     )
-    year_of = test_cal.holidays(start_datum, end_datum)
-    three_years_after = test_cal.holidays(
-        start_datum + DateOffset(years=3), end_datum + DateOffset(years=3)
+    check_year_of = test_cal.holidays(start, end)
+    check_after_edge = test_cal.holidays(
+        start + DateOffset(years=3), end + DateOffset(years=3)
     )
 
-    assert type(three_years_after) == type(year_of)
-    assert type(three_years_before) == type(year_of)
+    tm.assert_index_equal(check_after_edge, check_year_of)
+    tm.assert_index_equal(check_before_edge, check_year_of)
diff --git a/pandas/tseries/holiday.py b/pandas/tseries/holiday.py
@@ -322,7 +322,7 @@ def _reference_dates(self, start_date, end_date):
 
         return dates
 
-    def _apply_rule(self, dates):
+    def _apply_rule(self, dates: DatetimeIndex) -> DatetimeIndex:
         """
         Apply the given offset/observance to a DatetimeIndex of dates.
 
@@ -335,15 +335,8 @@ def _apply_rule(self, dates):
         -------
         Dates with rules applied
         """
-        # GH 49075
-        # If we have a half-open date interval with observance,
-        # ensure we return a DatetimeIndex
-        if (
-            self.observance is not None
-            and (self.start_date is not None and self.end_date is None)
-            or (self.end_date is not None and self.start_date is None)
-        ):
-            return DatetimeIndex([dates.map(lambda d: self.observance(d))])
+        if dates.empty:
+            return DatetimeIndex([])
 
         if self.observance is not None:
             return dates.map(lambda d: self.observance(d))