Fix recursive limit in find_next_time_expression_time (#58914)

* Fix recursive limit in find_next_time_expression_time

* Add test case

* Update test_event.py

Co-authored-by: Erik Montnemery <erik@montnemery.com>

homeassistant/util/dt.py

@@ -245,6 +245,16 @@ def _dst_offset_diff(dattim: dt.datetime) -> dt.timedelta:
     return (dattim + delta).utcoffset() - (dattim - delta).utcoffset()  # type: ignore[operator]
 
 
+def _lower_bound(arr: list[int], cmp: int) -> int | None:
+    """Return the first value in arr greater or equal to cmp.
+
+    Return None if no such value exists.
+    """
+    if (left := bisect.bisect_left(arr, cmp)) == len(arr):
+        return None
+    return arr[left]
+
+
 def find_next_time_expression_time(
     now: dt.datetime,  # pylint: disable=redefined-outer-name
     seconds: list[int],
@@ -263,15 +273,7 @@ def find_next_time_expression_time(
     if not seconds or not minutes or not hours:
         raise ValueError("Cannot find a next time: Time expression never matches!")
 
-    def _lower_bound(arr: list[int], cmp: int) -> int | None:
-        """Return the first value in arr greater or equal to cmp.
-
-        Return None if no such value exists.
-        """
-        if (left := bisect.bisect_left(arr, cmp)) == len(arr):
-            return None
-        return arr[left]
-
+    while True:
         # Reset microseconds and fold; fold (for ambiguous DST times) will be handled later
         result = now.replace(microsecond=0, fold=0)
 
@@ -325,9 +327,8 @@ def find_next_time_expression_time(
 
             # We solve this edge case by just iterating one second until the result exists
             # (max. 3600 operations, which should be fine for an edge case that happens once a year)
-        return find_next_time_expression_time(
-            result + dt.timedelta(seconds=1), seconds, minutes, hours
-        )
+            now += dt.timedelta(seconds=1)
+            continue
 
         now_is_ambiguous = _datetime_ambiguous(now)
         result_is_ambiguous = _datetime_ambiguous(result)

tests/helpers/test_event.py

@@ -3452,6 +3452,72 @@ async def test_periodic_task_entering_dst(hass):
     unsub()
 
 
+async def test_periodic_task_entering_dst_2(hass):
+    """Test periodic task behavior when entering dst.
+
+    This tests a task firing every second in the range 0..58 (not *:*:59)
+    """
+    timezone = dt_util.get_time_zone("Europe/Vienna")
+    dt_util.set_default_time_zone(timezone)
+    specific_runs = []
+
+    # DST starts early morning March 27th 2022
+    yy = 2022
+    mm = 3
+    dd = 27
+
+    # There's no 2022-03-27 02:00:00, the event should not fire until 2022-03-28 03:00:00
+    time_that_will_not_match_right_away = datetime(
+        yy, mm, dd, 1, 59, 59, tzinfo=timezone, fold=0
+    )
+    # Make sure we enter DST during the test
+    assert (
+        time_that_will_not_match_right_away.utcoffset()
+        != (time_that_will_not_match_right_away + timedelta(hours=2)).utcoffset()
+    )
+
+    with patch(
+        "homeassistant.util.dt.utcnow", return_value=time_that_will_not_match_right_away
+    ):
+        unsub = async_track_time_change(
+            hass,
+            callback(lambda x: specific_runs.append(x)),
+            second=list(range(59)),
+        )
+
+    async_fire_time_changed(
+        hass, datetime(yy, mm, dd, 1, 59, 59, 999999, tzinfo=timezone)
+    )
+    await hass.async_block_till_done()
+    assert len(specific_runs) == 0
+
+    async_fire_time_changed(
+        hass, datetime(yy, mm, dd, 3, 0, 0, 999999, tzinfo=timezone)
+    )
+    await hass.async_block_till_done()
+    assert len(specific_runs) == 1
+
+    async_fire_time_changed(
+        hass, datetime(yy, mm, dd, 3, 0, 1, 999999, tzinfo=timezone)
+    )
+    await hass.async_block_till_done()
+    assert len(specific_runs) == 2
+
+    async_fire_time_changed(
+        hass, datetime(yy, mm, dd + 1, 1, 59, 59, 999999, tzinfo=timezone)
+    )
+    await hass.async_block_till_done()
+    assert len(specific_runs) == 3
+
+    async_fire_time_changed(
+        hass, datetime(yy, mm, dd + 1, 2, 0, 0, 999999, tzinfo=timezone)
+    )
+    await hass.async_block_till_done()
+    assert len(specific_runs) == 4
+
+    unsub()
+
+
 async def test_periodic_task_leaving_dst(hass):
     """Test periodic task behavior when leaving dst."""
     timezone = dt_util.get_time_zone("Europe/Vienna")