Update HolidayBase::get_closest_holiday method

holidays/holiday_base.py

@@ -1136,10 +1136,14 @@ def get_closest_holiday(
             raise AttributeError(f"Unknown direction: {direction}")
 
         dt = self.__keytransform__(target_date or datetime.now().date())
-        if direction == "forward" and (next_year := dt.year + 1) not in self.years:
-            self._populate(next_year)
-        elif direction == "backward" and (previous_year := dt.year - 1) not in self.years:
-            self._populate(previous_year)
+        # Automatically expand for `expand=True` cases only, like `__keytransform__`.
+        if self.expand:
+            if direction == "forward" and (next_year := dt.year + 1) not in self.years:
+                self.years.add(next_year)
+                self._populate(next_year)
+            elif direction == "backward" and (previous_year := dt.year - 1) not in self.years:
+                self.years.add(previous_year)
+                self._populate(previous_year)
 
         sorted_dates = sorted(self.keys())
         position = (

tests/test_holiday_base.py

@@ -1477,6 +1477,38 @@ def test_get_closest_holiday_unsorted_calendars(self):
             (date(2024, 1, 15), "Martin Luther King Jr. Day"),
         )
 
+    def test_get_closest_holiday_updates_years(self):
+        # Searching forward should add the next year to self.years so that
+        # repeated calls do not re-populate the adjacent year.
+        us = US(years=2024)
+        self.assertEqual(us.years, {2024})
+
+        us.get_closest_holiday(date(2024, 12, 31), "forward")
+        self.assertIn(2025, us.years)
+
+        # Searching backward should add the previous year to self.years.
+        us2 = US(years=2024)
+        self.assertEqual(us2.years, {2024})
+
+        us2.get_closest_holiday(date(2024, 1, 1), "backward")
+        self.assertIn(2023, us2.years)
+
+    def test_get_closest_holiday_expand_false_keeps_state(self):
+        # With expand=False the object must not change state while accessed.
+        us = US(years=2024, expand=False)
+        keys_before = set(us.keys())
+
+        self.assertIsNone(us.get_closest_holiday(date(2024, 12, 31), "forward"))
+        self.assertEqual(us.years, {2024})
+        self.assertEqual(set(us.keys()), keys_before)
+
+        self.assertEqual(
+            us.get_closest_holiday(date(2024, 12, 31), "backward"),
+            (date(2024, 12, 25), "Christmas Day"),
+        )
+        self.assertEqual(us.years, {2024})
+        self.assertEqual(set(us.keys()), keys_before)
+
     def test_get_closest_holiday_invalid_direction(self):
         self.assertRaises(
             AttributeError, lambda: HolidayBase().get_closest_holiday(direction="invalid")