refactor(concurrency): Refactor ObserverContextStore to use OSAllocatedUnfairLock

The ObserverContextStore was converted from an actor to a final class, utilizing OSAllocatedUnfairLock for thread-safe synchronous access. This simplifies the ObserverInterceptor by removing unnecessary Task wrappers and associated await calls. The minimum macOS deployment target was also updated to v13.

Author: Šimon Šesták

Sources/GraphQLAPIKit/Interceptors/ObserverInterceptor.swift

@@ -31,17 +31,12 @@ struct ObserverInterceptor<Observer: GraphQLNetworkObserver>: ApolloInterceptor
         let requestId = urlRequest.hashValue.description
 
         if response == nil {
-            // BEFORE network fetch - call willSendRequest and store context
+            // BEFORE network fetch - call willSendRequest and store context synchronously
             let context = observer.willSendRequest(urlRequest)
-            Task {
-                await contextStore.store(context, for: requestId)
-            }
+            contextStore.store(context, for: requestId)
         } else {
             // AFTER network fetch - retrieve context and call didReceiveResponse
-            Task {
-                guard let context = await contextStore.retrieve(for: requestId) else {
-                    return
-                }
+            if let context = contextStore.retrieve(for: requestId) {
                 observer.didReceiveResponse(
                     for: urlRequest,
                     response: response?.httpResponse,
@@ -54,15 +49,9 @@ struct ObserverInterceptor<Observer: GraphQLNetworkObserver>: ApolloInterceptor
         // Wrap completion to handle errors
         let wrappedCompletion: (Result<GraphQLResult<Operation.Data>, Error>) -> Void = { result in
             if case .failure(let error) = result {
-                Task {
-                    guard let context = await contextStore.retrieve(for: requestId) else {
-                        completion(result)
-                        return
-                    }
+                if let context = contextStore.retrieve(for: requestId) {
                     observer.didFail(request: urlRequest, error: error, context: context)
-                    completion(result)
                 }
-                return
             }
             completion(result)
         }

Sources/GraphQLAPIKit/Observers/ObserverContextStore.swift

@@ -1,15 +1,16 @@
 import Foundation
+import os
 
-/// Actor that stores observer contexts keyed by request identifier.
+/// Thread-safe store for observer contexts keyed by request identifier.
 /// Enables two interceptor instances to share state across the interceptor chain.
-actor ObserverContextStore<Context> {
-    private var contexts: [String: Context] = [:]
+final class ObserverContextStore<Context: Sendable>: Sendable {
+    private let state = OSAllocatedUnfairLock(initialState: [String: Context]())
 
     func store(_ context: Context, for requestId: String) {
-        contexts[requestId] = context
+        state.withLock { $0[requestId] = context }
     }
 
     func retrieve(for requestId: String) -> Context? {
-        contexts.removeValue(forKey: requestId)
+        state.withLock { $0.removeValue(forKey: requestId) }
     }
 }

Tests/GraphQLAPIKitTests/GraphQLNetworkObserverTests.swift

@@ -87,25 +87,25 @@ final class GraphQLNetworkObserverTests: XCTestCase {
 
     // MARK: - Context Store Tests
 
-    func testContextStoreOperations() async {
+    func testContextStoreOperations() {
         let store = ObserverContextStore<String>()
 
         // Test store and retrieve
-        await store.store("context-1", for: "request-1")
-        await store.store("context-2", for: "request-2")
-        await store.store("context-3", for: "request-3")
+        store.store("context-1", for: "request-1")
+        store.store("context-2", for: "request-2")
+        store.store("context-3", for: "request-3")
 
         // Retrieve in different order
-        let context2 = await store.retrieve(for: "request-2")
-        let context1 = await store.retrieve(for: "request-1")
-        let context3 = await store.retrieve(for: "request-3")
+        let context2 = store.retrieve(for: "request-2")
+        let context1 = store.retrieve(for: "request-1")
+        let context3 = store.retrieve(for: "request-3")
 
         XCTAssertEqual(context1, "context-1")
         XCTAssertEqual(context2, "context-2")
         XCTAssertEqual(context3, "context-3")
 
         // Verify retrieve removes context
-        let secondRetrieve = await store.retrieve(for: "request-1")
+        let secondRetrieve = store.retrieve(for: "request-1")
         XCTAssertNil(secondRetrieve)
     }
 }