Calendar.RecurrenceRule: Only match weekday components when filtering by weekday (#1020)

When filtering by weekdays, we match the dates against a set of date components.
These components happened to contain the hour, minute and second components from
the anchor date, so filtering would undo previous expansions by hour, minute and
second.

Author: hristost

Sources/FoundationEssentials/Calendar/Calendar_Recurrence.swift

@@ -614,8 +614,7 @@ extension Calendar {
     ///   weekdays of intereset, or to filter a list of dates
     func _weekdayComponents(for weekdays: [Calendar.RecurrenceRule.Weekday],
                             in parent: Calendar.Component,
-                            anchor: Date,
-                            anchorComponents: DateComponents? = nil) -> [DateComponents]? {
+                            anchor: Date) -> [DateComponents]? {
         /// Map of weekdays to which occurences of the weekday we are interested
         /// in. `1` is the first such weekday in the interval, `-1` is the last.
         /// An empty array indicates that any weekday is valid
@@ -645,9 +644,6 @@ extension Calendar {
         } else {
             .weekOfYear
         }
-        /// The components we return for matching and enumeration
-        let componentSet: Calendar.ComponentSet = [.weekday, .hour, .minute, .second]
-        
 
         guard
             let interval = dateInterval(of: parent, for: anchor)
@@ -656,7 +652,6 @@ extension Calendar {
         lazy var weekRange = range(of: weekComponent, in: parent, for: anchor)!
 
         var result: [DateComponents] = []
-        let anchorComponents = anchorComponents ?? _dateComponents(componentSet, from: anchor)
 
         lazy var firstWeekday = component(.weekday, from: interval.start)
         // The end of the interval would always be midnight on the day after, so
@@ -667,15 +662,15 @@ extension Calendar {
         for (weekday, occurences) in map {
             let weekdayIdx = weekday.icuIndex
             if occurences == [] {
-                var components = anchorComponents
+                var components = DateComponents()
                 components.setValue(nil, for: weekComponent)
                 components.weekday = weekdayIdx
                 result.append(components)
             } else {
                 lazy var firstWeek = weekRange.lowerBound + (weekdayIdx < firstWeekday ? 1 : 0)
                 lazy var lastWeek  = weekRange.upperBound - (weekdayIdx > lastWeekday  ? 1 : 0)
                 for occurence in occurences {
-                    var components = anchorComponents
+                    var components = DateComponents()
                     if occurence > 0 {
                         components.setValue(firstWeek - 1 + occurence, for: weekComponent)
                     } else {
@@ -815,7 +810,7 @@ extension Calendar {
         if let weekdays = combinationComponents.weekdays {
             dates = try dates.flatMap { date, comps in
                 let parentComponent: Calendar.Component = .month
-                let weekdayComponents = _weekdayComponents(for: weekdays, in: parentComponent, anchor: date, anchorComponents: comps)
+                let weekdayComponents = _weekdayComponents(for: weekdays, in: parentComponent, anchor: date)
                 let dates = try weekdayComponents!.map { comps in 
                     var date = date
                     if let result = try dateAfterMatchingWeekOfYear(startingAt: date, components: comps, direction: .forward) {

Tests/FoundationEssentialsTests/GregorianCalendarRecurrenceRuleTests.swift

@@ -739,4 +739,31 @@ final class GregorianCalendarRecurrenceRuleTests: XCTestCase {
         XCTAssertEqual(dates.next(), Date(timeIntervalSince1970: 1767484800.0)) // 2026-01-04T00:00:00-0000
         XCTAssertEqual(dates.next(), Date(timeIntervalSince1970: 1799020800.0)) // 2027-01-04T00:00:00-0000
     }
+
+    func testWeekdayFilter() {
+        var alarms = Calendar.RecurrenceRule(calendar: gregorian, frequency: .daily)
+        alarms.weekdays = [.every(.monday), .every(.tuesday), .every(.wednesday), .every(.thursday), .every(.friday)]
+        alarms.hours = [7, 8]
+        alarms.minutes = [0, 15, 30, 45]
+
+        let start = Date(timeIntervalSince1970: 1695304800.0) // 2023-09-21T14:00:00-0000
+        var results = alarms.recurrences(of: start).makeIterator()
+
+        XCTAssertEqual(results.next(), Date(timeIntervalSince1970: 1695366000.0)) // 2023-09-22T07:00:00-0000
+        XCTAssertEqual(results.next(), Date(timeIntervalSince1970: 1695366900.0)) // 2023-09-22T07:15:00-0000
+        XCTAssertEqual(results.next(), Date(timeIntervalSince1970: 1695367800.0)) // 2023-09-22T07:30:00-0000
+        XCTAssertEqual(results.next(), Date(timeIntervalSince1970: 1695368700.0)) // 2023-09-22T07:45:00-0000
+        XCTAssertEqual(results.next(), Date(timeIntervalSince1970: 1695369600.0)) // 2023-09-22T08:00:00-0000
+        XCTAssertEqual(results.next(), Date(timeIntervalSince1970: 1695370500.0)) // 2023-09-22T08:15:00-0000
+        XCTAssertEqual(results.next(), Date(timeIntervalSince1970: 1695371400.0)) // 2023-09-22T08:30:00-0000
+        XCTAssertEqual(results.next(), Date(timeIntervalSince1970: 1695372300.0)) // 2023-09-22T08:45:00-0000
+        XCTAssertEqual(results.next(), Date(timeIntervalSince1970: 1695625200.0)) // 2023-09-25T07:00:00-0000
+        XCTAssertEqual(results.next(), Date(timeIntervalSince1970: 1695626100.0)) // 2023-09-25T07:15:00-0000
+        XCTAssertEqual(results.next(), Date(timeIntervalSince1970: 1695627000.0)) // 2023-09-25T07:30:00-0000
+        XCTAssertEqual(results.next(), Date(timeIntervalSince1970: 1695627900.0)) // 2023-09-25T07:45:00-0000
+        XCTAssertEqual(results.next(), Date(timeIntervalSince1970: 1695628800.0)) // 2023-09-25T08:00:00-0000
+        XCTAssertEqual(results.next(), Date(timeIntervalSince1970: 1695629700.0)) // 2023-09-25T08:15:00-0000
+        XCTAssertEqual(results.next(), Date(timeIntervalSince1970: 1695630600.0)) // 2023-09-25T08:30:00-0000
+        XCTAssertEqual(results.next(), Date(timeIntervalSince1970: 1695631500.0)) // 2023-09-25T08:45:00-0000
+    }
 }