Resolved issues where schedules crossed daylight savings boundaries (#139)

Resolved issue where a schedule was not correctly calculated if the daylight saving offset occurred on the next iteration of the schedule.
Resolved issue with .FirstOrDefault which was returning DateTime.MinValue if no schedule was found.

Author: CraigHawker

MFiles.VAF.Extensions.Tests/Configuration/ScheduledExecution/WeeklyTriggerTests.cs

@@ -193,5 +193,23 @@ public static IEnumerable<object[]> GetNextDayOfWeekData()
 				new DateTime ?[] { new DateTime(2021, 03, 20, 0, 0, 0, 0) }
 			};
 		}
+
+		[TestMethod]
+		public void WeeklyValueNotReturnedWhenDaylightsavingChanges()
+		{
+			var now = new DateTimeOffset(new DateTime(2024, 10, 23, 10, 27, 0), new TimeSpan(0, 0, 0));
+			var expected = new DateTimeOffset(new DateTime(2024, 10, 30, 9, 0, 0), new TimeSpan(2, 0, 0));
+
+			var trigger = new WeeklyTrigger()
+			{
+				TriggerTimes = new List<TimeSpan>()
+				{
+					new TimeSpan(9, 0, 0)
+				},
+				TriggerDays = new List<DayOfWeek>() { DayOfWeek.Wednesday }
+			};
+			var execution = trigger.GetNextExecution(now, TimeZoneInfo.FindSystemTimeZoneById("FLE Standard Time"));
+			Assert.AreEqual(expected.ToUniversalTime(), execution?.ToUniversalTime());
+		}
 	}
 }

MFiles.VAF.Extensions/Configuration/ScheduledExecution/DailyTrigger.cs

@@ -59,6 +59,7 @@ public DailyTrigger()
 			timeZoneInfo = timeZoneInfo ?? TimeZoneInfo.Local;
 
 			// When should we start looking?
+			var before = after.Value;
 			after = (after ?? DateTime.UtcNow).ToUniversalTime();
 
 			// Convert the time into the timezone we're after.
@@ -73,7 +74,12 @@ public DailyTrigger()
 						// What is the potential time that this will run?
 						DateTimeOffset potential;
 						{
-							var dateTime = after.Value.Date.Add(t);
+							// If the timezone conversion changed the date then go back to the start of the date.
+							var date = after.Value.Date;
+							if (after.Value.Date != before.Date)
+								date = new DateTime(before.Date.Ticks);
+
+							var dateTime = date.Add(t);
 							potential = new DateTimeOffset(dateTime, timeZoneInfo.GetUtcOffset(dateTime));
 						}
 

MFiles.VAF.Extensions/Configuration/ScheduledExecution/Schedule.cs

@@ -106,11 +106,11 @@ public class Schedule
 			}
 
 			// Get the next execution date from the triggers.
-			return this.Triggers?
+			var next = this.Triggers?
 				.Select(t => t.GetNextExecution(after, timeZoneInfo))
-				.Where(d => d.HasValue)
-				.OrderBy(d => d)
-				.FirstOrDefault();
+				.Where(d => d.HasValue && d.Value.DateTime != DateTime.MinValue)
+				.OrderBy(d => d);
+			return next.Any() ? next.First() : null;
 		}
 
 

MFiles.VAF.Extensions/Configuration/ScheduledExecution/WeeklyTrigger.cs

@@ -74,13 +74,12 @@ public WeeklyTrigger()
 				.Select(d => d.Value)
 				.Where(d => d > after.Value)
 				.OrderBy(d => d)
+				.Select(d => d.ToUniversalTime())
 				.ToList();
 
 			this.Logger?.Trace($"These are the potential matches: {string.Join(", ", potentialMatches)}");
 
-			return potentialMatches
-				.Select(d => d.ToUniversalTime())
-				.FirstOrDefault();
+			return potentialMatches.Any() ? (DateTimeOffset?)potentialMatches.First() : null;
 		}
 
 		/// <summary>