Fire the notification unconditionally, and check that it is posted in the test.

Author: millenomi

Foundation/UserDefaults.swift

@@ -359,39 +359,29 @@ open class UserDefaults: NSObject {
 
     open func setPersistentDomain(_ domain: [String : Any], forName domainName: String) {
         if let defaults = UserDefaults(suiteName: domainName) {
-            var removedAny = false
             for key in defaults._dictionaryRepresentation(searchingOutsideOfSuite: false).keys {
                 defaults.removeObject(forKey: key)
-                removedAny = true
             }
 
-            var addedAny = false
             for (key, value) in domain {
                 defaults.set(value, forKey: key)
-                addedAny = true
             }
 
             _ = defaults.synchronize()
 
-            if removedAny || addedAny {
-                NotificationCenter.default.post(name: UserDefaults.didChangeNotification, object: self)
-            }
+            NotificationCenter.default.post(name: UserDefaults.didChangeNotification, object: self)
         }
     }
 
     open func removePersistentDomain(forName domainName: String) {
         if let defaults = UserDefaults(suiteName: domainName) {
-            var removedAny = false
             for key in defaults._dictionaryRepresentation(searchingOutsideOfSuite: false).keys {
                 defaults.removeObject(forKey: key)
-                removedAny = true
             }
 
             _ = defaults.synchronize()
 
-            if removedAny {
-                NotificationCenter.default.post(name: UserDefaults.didChangeNotification, object: self)
-            }
+            NotificationCenter.default.post(name: UserDefaults.didChangeNotification, object: self)
         }
     }
 

TestFoundation/TestUserDefaults.swift

@@ -299,6 +299,21 @@ class TestUserDefaults : XCTestCase {
 		let dictionary = (key: "A Dictionary", value: [ "Swift": "Imperative", "Haskell": "Functional", "LISP": "LISP", "Today": Date() ] as [String: AnyHashable])
 
 		let domainName = "org.swift.Foundation.TestPersistentDomainName"
+
+		let done = expectation(description: "All notifications have fired.")
+		
+		var countOfFiredNotifications = 0
+		let expectedNotificationCount = 3
+		
+		let observer = NotificationCenter.default.addObserver(forName: UserDefaults.didChangeNotification, object: nil, queue: .main) { (_) in
+			countOfFiredNotifications += 1
+			
+			if countOfFiredNotifications == expectedNotificationCount {
+				done.fulfill()
+			} else if countOfFiredNotifications > expectedNotificationCount {
+				XCTFail("Too many UserDefaults.didChangeNotification notifications posted.")
+			}
+		}
 
 		let defaults1 = UserDefaults(suiteName: nil)!
 
@@ -335,5 +350,9 @@ class TestUserDefaults : XCTestCase {
 		if let domain = defaults3.persistentDomain(forName: domainName) {
 			XCTAssertEqual(domain.count, 0)
 		} // else it's nil, which is also OK.
+		
+		waitForExpectations(timeout: 10)
+		
+		NotificationCenter.default.removeObserver(observer)
 	}
 }