Swift 6 migration for NSE (#5608)

* swift 6 support for NSE and concurrency safe implementations for it

* enforcing required Sendable conformance for swift 6 migration in NSE

* use Mutex to access the string builder cache

* use an async stream to update timeline items diffs

* fix for Sendable appHooks

ElementX/Sources/Other/CurrentValuePublisher.swift

@@ -10,7 +10,9 @@ import Combine
 
 /// A wrapper of CurrentValueSubject.
 /// The purpose of this type is to remove the possibility to send new values on the underlying subject.
-struct CurrentValuePublisher<Output, Failure: Error>: Publisher {
+///
+/// `CurrentValueSubject` is documented as thread-safe but is not formally `Sendable`, hence `@unchecked`.
+struct CurrentValuePublisher<Output, Failure: Error>: Publisher, @unchecked Sendable {
     private let subject: CurrentValueSubject<Output, Failure>
     
     init(_ subject: CurrentValueSubject<Output, Failure>) {

ElementX/Sources/Other/ExpiringTaskRunner.swift

@@ -15,9 +15,9 @@ enum ExpiringTaskRunnerError: Error {
 actor ExpiringTaskRunner<T: Sendable> {
     private var continuation: CheckedContinuation<T, Error>?
     
-    private var task: () async throws -> T
-    
-    init(_ task: @escaping () async throws -> T) {
+    private var task: @Sendable () async throws -> T
+
+    init(_ task: @escaping @Sendable () async throws -> T) {
         self.task = task
     }
     

ElementX/Sources/Other/Extensions/Bundle.swift

@@ -7,6 +7,7 @@
 //
 
 import Foundation
+import Synchronization
 
 public extension Bundle {
     /// The top-level bundle that contains the entire app.
@@ -24,12 +25,12 @@ public extension Bundle {
     
     // MARK: - Localisation
     
-    /// Overrides `Bundle.app.preferredLocalizations` for testing translations.
-    static var overrideLocalizations: [String]?
-    
-    private static let cacheDispatchQueue = DispatchQueue(label: "io.element.elementx.localization_bundle_cache")
-    private static var cachedBundles = [String: Bundle]()
-    
+    /// Overrides `Bundle.app.preferredLocalizations` for testing translations since this is
+    /// only for testing, and is changed at runtime only in tests, it's fine to keep as `nonisolated(unsafe)`
+    nonisolated(unsafe) static var overrideLocalizations: [String]?
+
+    private static let cachedBundles = Mutex<[String: Bundle]>([:])
+
     /// Get an lproj language bundle from the receiver bundle.
     /// - Parameter language: The language to try to load.
     /// - Returns: The lproj bundle if found otherwise nil.
@@ -37,32 +38,25 @@ public extension Bundle {
         if let bundle = cachedValue(forKey: language) {
             return bundle
         }
-        
+
         guard let lprojURL = Bundle.app.url(forResource: language, withExtension: "lproj") else {
             return nil
         }
-        
+
         let bundle = Bundle(url: lprojURL)
-        
+
         cacheValue(bundle, forKey: language)
-        
+
         return bundle
     }
-    
+
     // MARK: - Private
-    
+
     private static func cacheValue(_ value: Bundle?, forKey key: String) {
-        cacheDispatchQueue.sync {
-            cachedBundles[key] = value
-        }
+        cachedBundles.withLock { $0[key] = value }
     }
-    
+
     private static func cachedValue(forKey key: String) -> Bundle? {
-        var result: Bundle?
-        cacheDispatchQueue.sync {
-            result = cachedBundles[key]
-        }
-        
-        return result
+        cachedBundles.withLock { $0[key] }
     }
 }

ElementX/Sources/Other/HTMLParsing/AttributedStringBuilder.swift

@@ -10,6 +10,7 @@ import Compound
 import LRUCache
 import MatrixRustSDK
 import SwiftSoup
+import Synchronization
 import UIKit
 
 protocol MentionBuilderProtocol {
@@ -42,11 +43,10 @@ struct AttributedStringBuilder: AttributedStringBuilderProtocol {
     private let mentionBuilder: MentionBuilderProtocol
     
     private static let attributeMSC4286 = "msc4286-external-payment-details"
-    private static let cacheDispatchQueue = DispatchQueue(label: "io.element.elementx.attributed_string_builder_v2_cache")
-    private static var caches: [String: LRUCache<String, AttributedString>] = [:]
+    private static let caches = Mutex<[String: LRUCache<String, AttributedString>]>([:])
 
     static func invalidateCaches() {
-        caches.removeAll()
+        caches.withLock { $0.removeAll() }
     }
     
     init(cacheKey: String = defaultKey, mentionBuilder: MentionBuilderProtocol) {
@@ -279,22 +279,17 @@ struct AttributedStringBuilder: AttributedStringBuilderProtocol {
     }
     
     private static func cacheValue(_ value: AttributedString?, forKey key: String, cacheKey: String) {
-        cacheDispatchQueue.sync {
+        caches.withLock { caches in
             if caches[cacheKey] == nil {
                 caches[cacheKey] = LRUCache<String, AttributedString>(countLimit: 1000)
             }
-            
+
             caches[cacheKey]?.setValue(value, forKey: key)
         }
     }
-    
+
     private static func cachedValue(forKey key: String, cacheKey: String) -> AttributedString? {
-        var result: AttributedString?
-        cacheDispatchQueue.sync {
-            result = caches[cacheKey]?.value(forKey: key)
-        }
-        
-        return result
+        caches.withLock { $0[cacheKey]?.value(forKey: key) }
     }
     
     // swiftlint:disable:next cyclomatic_complexity

ElementX/Sources/Other/Logging/Tracing.swift

@@ -22,7 +22,7 @@ enum Tracing {
     /// Set this to temporarily override the directory from which logs will be collected.
     /// This basically only affects ``logFiles``, and doesn't inform the SDK to write
     /// the logs to a different directory, which should be done before setting this.
-    static var logsDirectoryOverride: URL?
+    nonisolated(unsafe) static var logsDirectoryOverride: URL?
     static var legacyLogsDirectory: URL {
         .appGroupContainerDirectory
     }

ElementX/Sources/Other/SDKListener.swift

@@ -13,12 +13,12 @@ import MatrixRustSDK
 ///
 /// To use this you'll need to add a conformance to the required listener
 /// protocol with a specialisation for the type it listens for.
-final class SDKListener<T> {
-    private let onUpdateClosure: (T) -> Void
-    
+final class SDKListener<T>: Sendable {
+    private let onUpdateClosure: @Sendable (T) -> Void
+
     /// Creates a new listener.
     /// - Parameter onUpdateClosure: A closure that will be called whenever a new value is available.
-    init(_ onUpdateClosure: @escaping (T) -> Void) {
+    init(_ onUpdateClosure: @escaping @Sendable (T) -> Void) {
         self.onUpdateClosure = onUpdateClosure
     }
 }