Adds publisher function, accepting array of keys

Sources/Defaults/Observation+Combine.swift

@@ -102,7 +102,7 @@ extension Defaults {
 	- Warning: This method exists for backwards compatibility and will be deprecated sometime in the future. Use ``Defaults/updates(_:initial:)-9eh8`` instead.
 	*/
 	public static func publisher(
-		keys: _AnyKey...,
+		keys: [_AnyKey],
 		options: ObservationOptions = [.initial]
 	) -> AnyPublisher<Void, Never> {
 		let initial = Empty<Void, Never>(completeImmediately: false).eraseToAnyPublisher()
@@ -118,4 +118,16 @@ extension Defaults {
 					combined.merge(with: keyPublisher).eraseToAnyPublisher()
 				}
 	}
+
+	/**
+	Publisher for multiple `Key<T>` observation, but without specific information about changes.
+
+	 - Warning: This method exists for backwards compatibility and will be deprecated sometime in the future. Use ``Defaults/updates(_:initial:)-9eh8`` instead.
+	*/
+	public static func publisher(
+		keys: _AnyKey...,
+		options: ObservationOptions = [.initial]
+	) -> AnyPublisher<Void, Never> {
+		self.publisher(keys: keys, options: options)
+	}
 }

Sources/Defaults/Observation.swift

@@ -125,6 +125,7 @@ extension Defaults {
 		private weak var object: UserDefaults?
 		private let key: String
 		private let callback: Callback
+		private var isObserving = false
 
 		init(object: UserDefaults, key: String, callback: @escaping Callback) {
 			self.object = object
@@ -138,10 +139,15 @@ extension Defaults {
 
 		func start(options: ObservationOptions) {
 			object?.addObserver(self, forKeyPath: key, options: options.toNSKeyValueObservingOptions, context: nil)
+			isObserving = true
 		}
 
 		func invalidate() {
-			object?.removeObserver(self, forKeyPath: key, context: nil)
+			if isObserving {
+				object?.removeObserver(self, forKeyPath: key, context: nil)
+				isObserving = false
+			}
+
 			object = nil
 			lifetimeAssociation?.cancel()
 		}

Tests/DefaultsTests/DefaultsTests.swift

@@ -733,6 +733,23 @@ final class DefaultsTests: XCTestCase {
 		waitForExpectations(timeout: 10)
 	}
 
+	func testImmediatelyFinishingMultiplePublisherCombine() {
+		let key1 = Defaults.Key<Bool>("observeKey1", default: false)
+		let key2 = Defaults.Key<String>("observeKey2", default: "🦄")
+		let expect = expectation(description: "Observation closure being called without crashing")
+
+		let cancellable = Defaults
+			.publisher(keys: [key1, key2], options: [.initial])
+			.first()
+			.sink { _ in
+				expect.fulfill()
+			}
+
+		cancellable.cancel()
+
+		waitForExpectations(timeout: 10)
+	}
+
 	func testKeyEquatable() {
 		XCTAssertEqual(Defaults.Key<Bool>("equatableKeyTest", default: false), Defaults.Key<Bool>("equatableKeyTest", default: false))
 	}