Make RedisConnection.Configuration.defaultPort thread safe (#81)

`RedisConnection.Configuration.defaultPort` is currently unprotected shared mutable state. To ensure thread safety this patch adds an atomic to back this property. Since setting the `defaultPort` doesn't make much sense for adopters, we deprecate the setter. Lastly we mark `RedisConnection.Configuration` as `Sendable`.

Sources/RediStack/RedisConnection+Configuration.swift

@@ -12,19 +12,31 @@
 //
 //===----------------------------------------------------------------------===//
 
+import Atomics
 import NIOCore
+import NIOConcurrencyHelpers
 import NIOPosix
 import Logging
 import struct Foundation.URL
 import protocol Foundation.LocalizedError
 
 extension RedisConnection {
     /// A configuration object for creating a single connection to Redis.
-    public struct Configuration {
+    public struct Configuration: Sendable {
+        private static let _defaultPortAtomic = ManagedAtomic(6379)
+
         /// The default port that Redis uses.
         ///
         /// See [https://redis.io/topics/quickstart](https://redis.io/topics/quickstart)
-        public static var defaultPort = 6379
+        public static var defaultPort: Int {
+            get {
+                self._defaultPortAtomic.load(ordering: .acquiring)
+            }
+            @available(*, deprecated, message: "Setting the default Redis port will be removed in the next major release")
+            set {
+                self._defaultPortAtomic.store(newValue, ordering: .releasing)
+            }
+        }
 
         internal static let defaultLogger = Logger.redisBaseConnectionLogger
 

Tests/RediStackTests/RedisConnection+ConfigurationTests.swift

@@ -0,0 +1,34 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the RediStack open source project
+//
+// Copyright (c) 2023 RediStack project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of RediStack project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import RediStack
+import XCTest
+
+final class RedisConnection_ConfigurationTest: XCTestCase {
+
+    func testGetDefaultRedisPort() {
+        XCTAssertEqual(RedisConnection.Configuration.defaultPort, 6379)
+    }
+
+    @available(*, deprecated, message: "Testing deprecated functionality")
+    func testGetAndSetTheDefaultRedisPort() {
+        XCTAssertEqual(RedisConnection.Configuration.defaultPort, 6379)
+        RedisConnection.Configuration.defaultPort = 1234
+        XCTAssertEqual(RedisConnection.Configuration.defaultPort, 1234)
+
+        // reset the default port
+        RedisConnection.Configuration.defaultPort = 6379
+    }
+}
+