GetOccurrences should not cache the results of a previous evaluation

[rianjs]

Recurrable components are mutable -- rules can be created at will, so caching the result of a previous computation is potentially invalid:

[Test]
public void AddExDateToEventAfterGetOccurrencesShouldRecomputeResult()
{
    var searchStart = _now.AddDays(-1);
    var searchEnd = _now.AddDays(7);
    var e = GetEventWithRecurrenceRules();
    var occurrences = e.GetOccurrences(searchStart, searchEnd);
    Assert.IsTrue(occurrences.Count == 5);

    var exDate = _now.AddDays(1);
    var period = new Period(new CalDateTime(exDate));
    var periodList = new PeriodList {period};
    e.ExceptionDates.Add(periodList);
    occurrences = e.GetOccurrences(searchStart, searchEnd);
    Assert.IsTrue(occurrences.Count == 4);

    //Specifying just a date should "black out" that date
    var excludeTwoDaysFromNow = _now.AddDays(2).Date;
    period = new Period(new CalDateTime(excludeTwoDaysFromNow));
    periodList.Add(period);
    occurrences = e.GetOccurrences(searchStart, searchEnd);
    Assert.IsTrue(occurrences.Count == 3);
}

private static readonly DateTime _now = DateTime.Now;
private static readonly DateTime _later = _now.AddHours(1);
private static Event GetEventWithRecurrenceRules()
{
    var dailyForFiveDays = new RecurrencePattern(FrequencyType.Daily, 1)
    {
        Count = 5,
    };

    var calendarEvent = new Event
    {
        Start = new CalDateTime(_now),
        End = new CalDateTime(_later),
        RecurrenceRules = new List<IRecurrencePattern> { dailyForFiveDays },
        Resources = new HashSet<string>(new[] {"Foo", "Bar", "Baz"}),
    };
    return calendarEvent;
}

EXDATE values that specify only a date should "black out" occurrences where the start time of the event falls on that date.

[rianjs]

de1f045

Available in nuget version 2.2.29

[LucBrainpact]

I've run across an issue with the current fix today:
An EXDATE with datetime at midnight also "blacks out" all occurrences that fall on that date.

BEGIN:VEVENT
DTEND;TZID=Europe/Amsterdam:20180308T040000
DTSTAMP:20180322T094247Z
DTSTART;TZID=Europe/Amsterdam:20180308T040000
EXDATE:20180309T000000
RRULE:FREQ=HOURLY;INTERVAL=4
SEQUENCE:0
UID:9f449bf5-c4ec-48cb-8a29-439d9088e14c
END:VEVENT

In the example above all occurrences on March 9th are excluded, the expected result was only the occurrence at midnight was excluded.