Add NotificationCenter dependency (#385)

* Add `NotificationCenter` dependency

With XCTest we recommended using the default center since tests were
pretty much quarantined to their own processes, but with Swift Testing,
that's changed, so controlling this dependency is worth a new API.

* Modernize CI

* wip

Author: stephencelis

.github/workflows/ci.yml

@@ -34,31 +34,10 @@ jobs:
       - name: Build for library evolution
         run: make build-for-library-evolution
 
-  macos-14:
-    name: macOS 14
-    runs-on: macos-14
-    strategy:
-      matrix:
-        config: ['debug', 'release']
-        xcode: ['15.4']
-    steps:
-      - uses: actions/checkout@v4
-      - name: Select Xcode ${{ matrix.xcode }}
-        run: sudo xcode-select -s /Applications/Xcode_${{ matrix.xcode }}.app
-      - name: Skip macro validation
-        run: defaults write com.apple.dt.Xcode IDESkipMacroFingerprintValidation -bool YES
-      - name: Run tests
-        run: make test-swift
-      - name: Build platforms ${{ matrix.config }}
-        run: CONFIG=${{ matrix.config }} make build-all-platforms
-      - name: Build for library evolution
-        run: make build-for-library-evolution
-
   ubuntu:
     strategy:
       matrix:
         swift:
-          - '5.10'
           - '6.0'
     name: Ubuntu (Swift ${{ matrix.swift }})
     runs-on: ubuntu-latest

Makefile

@@ -31,7 +31,7 @@ test-linux:
 		--rm \
 		-v "$(PWD):$(PWD)" \
 		-w "$(PWD)" \
-		swift:5.10-focal \
+		swift:6.1-focal \
 		bash -c 'apt-get update && apt-get -y install make && make test-swift'
 
 build-for-static-stdlib:
@@ -61,12 +61,12 @@ build-for-static-stdlib-docker:
 	@docker run \
 		-v "$(PWD):$(PWD)" \
 		-w "$(PWD)" \
-		swift:5.9-focal \
+		swift:6.1-focal \
 		bash -c "swift build -c debug --static-swift-stdlib"
 	@docker run \
 		-v "$(PWD):$(PWD)" \
 		-w "$(PWD)" \
-		swift:5.9-focal \
+		swift:6.1-focal \
 		bash -c "swift build -c release --static-swift-stdlib"
 
 format:

Sources/Dependencies/DependencyValues/NotificationCenter.swift

@@ -0,0 +1,31 @@
+#if canImport(Foundation)
+  import Foundation
+
+  extension DependencyValues {
+    /// The notification center that features should use.
+    ///
+    /// By default, `NotificationCenter.default` is provided. When used in tests, a task-local
+    /// center is provided, instead.
+    ///
+    /// You can access notification center from a feature by introducing a ``Dependency`` property
+    /// wrapper to the property:
+    ///
+    /// ```swift
+    /// @Observable
+    /// final class FeatureModel {
+    ///   @ObservationIgnored
+    ///   @Dependency(\.notificationCenter) var notificationCenter
+    ///   // ...
+    /// }
+    /// ```
+    public var notificationCenter: NotificationCenter {
+      get { self[NotificationCenterKey.self] }
+      set { self[NotificationCenterKey.self] = newValue }
+    }
+
+    private enum NotificationCenterKey: DependencyKey {
+      static let liveValue = NotificationCenter.default
+      static var testValue: NotificationCenter { NotificationCenter() }
+    }
+  }
+#endif

Sources/Dependencies/Documentation.docc/Extensions/DependencyValues.md

@@ -30,6 +30,7 @@
 - ``locale``
 - ``mainQueue``
 - ``mainRunLoop``
+- ``notificationCenter``
 - ``openURL``
 - ``precondition``
 - ``suspendingClock``

Tests/DependenciesTests/NotificationCenterTests.swift

@@ -0,0 +1,75 @@
+#if canImport(Combine)
+  import Combine
+  import Dependencies
+  import Foundation
+  import Testing
+
+  func post() {
+    @Dependency(\.notificationCenter) var notificationCenter
+    notificationCenter.post(Notification(name: notificationName))
+  }
+
+  private let notificationName = Notification.Name("Hello")
+
+  struct NotificationCenterTests {
+    @Dependency(\.notificationCenter) var notificationCenter
+    var cancellables: Set<AnyCancellable> = []
+
+    @Test mutating func basics() {
+      var defaultReceived = 0
+      var dependencyReceived = 0
+      NotificationCenter.default
+        .publisher(for: notificationName).sink { _ in defaultReceived += 1 }
+        .store(in: &cancellables)
+      notificationCenter
+        .publisher(for: notificationName).sink { _ in dependencyReceived += 1 }
+        .store(in: &cancellables)
+      post()
+      #expect(defaultReceived == 0)
+      #expect(dependencyReceived == 1)
+    }
+
+    @Test mutating func concurrent1() async throws {
+      nonisolated(unsafe) var count = 0
+      notificationCenter
+        .publisher(for: notificationName)
+        .sink { _ in count += 1 }
+        .store(in: &cancellables)
+
+      for _ in 1...100 {
+        notificationCenter.post(name: notificationName, object: nil)
+        try await Task.sleep(for: .milliseconds(1))
+      }
+      #expect(count == 100)
+    }
+
+    @Test mutating func concurrent2() async throws {
+      nonisolated(unsafe) var count = 0
+      notificationCenter
+        .publisher(for: notificationName)
+        .sink { _ in count += 1 }
+        .store(in: &cancellables)
+
+      for _ in 1...100 {
+        notificationCenter.post(name: notificationName, object: nil)
+        try await Task.sleep(for: .milliseconds(1))
+      }
+      #expect(count == 100)
+    }
+
+    @Test
+    mutating func concurrent3() async throws {
+      nonisolated(unsafe) var count = 0
+      notificationCenter
+        .publisher(for: notificationName)
+        .sink { _ in count += 1 }
+        .store(in: &cancellables)
+
+      for _ in 1...100 {
+        notificationCenter.post(name: notificationName, object: nil)
+        try await Task.sleep(for: .milliseconds(1))
+      }
+      #expect(count == 100)
+    }
+  }
+#endif