Implementation of NSDateComponents.copy(with: zone)

Foundation/NSCalendar.swift

@@ -1428,7 +1428,27 @@ open class NSDateComponents : NSObject, NSCopying, NSSecureCoding {
     }
 
     open func copy(with zone: NSZone? = nil) -> Any {
-        NSUnimplemented()
+        let newObj = NSDateComponents()
+        newObj.calendar = calendar
+        newObj.timeZone = timeZone
+        newObj.era = era
+        newObj.year = year
+        newObj.month = month
+        newObj.day = day
+        newObj.hour = hour
+        newObj.minute = minute
+        newObj.second = second
+        newObj.nanosecond = nanosecond
+        newObj.weekOfYear = weekOfYear
+        newObj.weekOfMonth = weekOfMonth
+        newObj.yearForWeekOfYear = yearForWeekOfYear
+        newObj.weekday = weekday
+        newObj.weekdayOrdinal = weekdayOrdinal
+        newObj.quarter = quarter
+        if leapMonthSet {
+            newObj.isLeapMonth = isLeapMonth
+        }
+        return newObj
     }
 
     /*@NSCopying*/ open var calendar: Calendar? {

TestFoundation/TestNSCalendar.swift

@@ -90,3 +90,34 @@ class TestNSCalendar: XCTestCase {
         XCTAssertEqual(copy.minimumDaysInFirstWeek, 2)
     }
 }
+
+class TestNSDateComponents: XCTestCase {
+
+    static var allTests: [(String, (TestNSDateComponents) -> () throws -> Void)] {
+        return [
+            ("test_copyNSDateComponents", test_copyNSDateComponents),
+        ]
+    }
+
+    func test_copyNSDateComponents() {
+        let components = NSDateComponents()
+        components.year = 1987
+        components.month = 3
+        components.day = 17
+        components.hour = 14
+        components.minute = 20
+        components.second = 0
+        let copy = components.copy(with: nil) as! NSDateComponents
+        XCTAssertTrue(components.isEqual(copy))
+        XCTAssertTrue(components == copy)
+        XCTAssertFalse(components === copy)
+        XCTAssertEqual(copy.year, 1987)
+        XCTAssertEqual(copy.month, 3)
+        XCTAssertEqual(copy.day, 17)
+        XCTAssertEqual(copy.isLeapMonth, false)
+        //Mutate NSDateComponents and verify that it does not reflect in the copy
+        components.hour = 12
+        XCTAssertEqual(components.hour, 12)
+        XCTAssertEqual(copy.hour, 14)
+    }
+}

TestFoundation/main.swift

@@ -30,6 +30,7 @@ XCTMain([
     testCase(TestNSCompoundPredicate.allTests),
     testCase(TestNSData.allTests),
     testCase(TestNSDate.allTests),
+    testCase(TestNSDateComponents.allTests),
     testCase(TestNSDateFormatter.allTests),
     testCase(TestNSDictionary.allTests),
     testCase(TestNSFileManager.allTests),