fix: reduce ObjectiveC need

Sources/SnapshotTesting/Plugins/PluginRegistry.swift

@@ -1,14 +1,16 @@
-#if canImport(SwiftUI) && canImport(ObjectiveC)
 import Foundation
-import ObjectiveC.runtime
 import SnapshotTestingPlugin
 
+#if canImport(ObjectiveC)
+import ObjectiveC.runtime
+#endif
+
 /// A singleton class responsible for managing and registering plugins conforming to the `SnapshotTestingPlugin` protocol.
 ///
 /// The `PluginRegistry` automatically discovers and registers classes conforming to the `SnapshotTestingPlugin` protocol
 /// within the Objective-C runtime. It allows retrieval of specific plugins by identifier, access to all registered plugins,
 /// and filtering of plugins that conform to the `ImageSerialization` protocol.
-public class PluginRegistry {
+class PluginRegistry {
 
   /// Shared singleton instance of `PluginRegistry`.
   private static let shared = PluginRegistry()
@@ -23,27 +25,27 @@ public class PluginRegistry {
     defer { automaticPluginRegistration() }
   }
 
-  // MARK: - Public Methods
+  // MARK: - Internal Methods
 
   /// Registers a plugin.
   ///
   /// - Parameter plugin: An instance conforming to `SnapshotTestingPlugin`.
-  public static func registerPlugin(_ plugin: SnapshotTestingPlugin) {
+  static func registerPlugin(_ plugin: SnapshotTestingPlugin) {
     PluginRegistry.shared.registerPlugin(plugin)
   }
 
   /// Retrieves a plugin by its identifier, casting it to the specified type.
   ///
   /// - Parameter identifier: The unique identifier for the plugin.
   /// - Returns: The plugin instance cast to `Output` if found and castable, otherwise `nil`.
-  public static func plugin<Output>(for identifier: String) -> Output? {
+  static func plugin<Output>(for identifier: String) -> Output? {
     PluginRegistry.shared.plugin(for: identifier)
   }
 
   /// Returns all registered plugins cast to the specified type.
   ///
   /// - Returns: An array of all registered plugins that can be cast to `Output`.
-  public static func allPlugins<Output>() -> [Output] {
+  static func allPlugins<Output>() -> [Output] {
     PluginRegistry.shared.allPlugins()
   }
 
@@ -71,6 +73,7 @@ public class PluginRegistry {
     return Array(plugins.values.compactMap { $0 as? Output })
   }
 
+#if canImport(ObjectiveC)
   /// Discovers and registers all classes conforming to the `SnapshotTestingPlugin` protocol.
   ///
   /// This method iterates over all Objective-C runtime classes, identifying those that conform to `SnapshotTestingPlugin`,
@@ -94,16 +97,16 @@ public class PluginRegistry {
       self.registerPlugin(pluginType.init())
     }
   }
+#endif
 
   // TEST-ONLY Reset Method
-  #if DEBUG
+#if DEBUG
   internal static func reset() {
-      shared.plugins.removeAll()
+    shared.plugins.removeAll()
   }
-
+  
   internal static func automaticPluginRegistration() {
-      shared.automaticPluginRegistration()
+    shared.automaticPluginRegistration()
   }
-  #endif
-}
 #endif
+}

Sources/SnapshotTestingPlugin/SnapshotTestingPlugin.swift

@@ -8,7 +8,8 @@ import Foundation
 /// environments where both Foundation and Objective-C are available, making it compatible with Objective-C runtime features.
 ///
 /// Conforming classes must be marked with `@objc` to ensure compatibility with Objective-C runtime mechanisms.
-@objc public protocol SnapshotTestingPlugin {
+@objc
+public protocol SnapshotTestingPlugin: AnyObject {
 
   /// A unique string identifier for the plugin.
   ///

Tests/SnapshotTestingTests/PluginRegistryTests.swift

@@ -1,26 +1,21 @@
-#if canImport(SwiftUI) && canImport(ObjectiveC)
+#if canImport(SwiftUI)
 import XCTest
-import ObjectiveC
 @testable import SnapshotTesting
 import SnapshotTestingPlugin
 
-class MockPlugin: NSObject, SnapshotTestingPlugin {
-  static var identifier: String = "MockPlugin"
+final class PluginRegistryTests: XCTestCase {
 
-  required override init() {
-    super.init()
+  class MockPlugin: SnapshotTestingPlugin {
+    static var identifier: String = "MockPlugin"
+
+    required init() {}
   }
-}
-
-class AnotherMockPlugin: NSObject, SnapshotTestingPlugin {
-  static var identifier: String = "AnotherMockPlugin"
 
-  required override init() {
-    super.init()
+  class AnotherMockPlugin: SnapshotTestingPlugin {
+    static var identifier: String = "AnotherMockPlugin"
+
+    required init() {}
   }
-}
-
-final class PluginRegistryTests: XCTestCase {
 
   override func setUp() {
     super.setUp()
@@ -60,14 +55,15 @@ final class PluginRegistryTests: XCTestCase {
     XCTAssertTrue(allPlugins.contains { $0 is AnotherMockPlugin })
   }
 
+#if canImport(ObjectiveC)
   func testAutomaticPluginRegistration() {
     // Automatically register plugins using the Objective-C runtime
-    PluginRegistry.automaticPluginRegistration() // Reset state before each test
+    PluginRegistry.automaticPluginRegistration()
 
     // Verify if the mock plugin was automatically registered
     let registeredPlugin: MockPlugin? = PluginRegistry.plugin(for: MockPlugin.identifier)
     XCTAssertNotNil(registeredPlugin)
   }
+#endif
 }
-
 #endif