Enable Swift 6 language mode (#46)

* Entire package now uses Swift 6 language mode.
* Increased thread-safety for `Node` modifications in `MoveTree` to
ensure sendability

CHANGELOG.md

@@ -1,8 +1,13 @@
 # [unreleased]
 
+### New Features
 * `BoardDelegate` now notifies when king is in check, and provides the color of the checked king, see [Issue #38](https://github.com/chesskit-app/chesskit-swift/issues/38).
 * `Move.checkState` and `Move.disambiguation` are now publicly accessible, see [Issue #38](https://github.com/chesskit-app/chesskit-swift/issues/38).
 
+### Technical Changes
+* Enable Swift 6 language mode package-wide.
+* `Game` and `MoveTree` are now `Sendable` types.
+
 # ChessKit 0.12.1
 Released Wednesday, September 11, 2024.
 

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version: 5.9
+// swift-tools-version: 6.0
 
 import PackageDescription
 
@@ -12,22 +12,10 @@ let package = Package(
     .watchOS(.v6)
   ],
   products: [
-    .library(
-      name: "ChessKit",
-      targets: ["ChessKit"]
-    )
+    .library(name: "ChessKit", targets: ["ChessKit"])
   ],
   targets: [
-    .target(
-      name: "ChessKit",
-      dependencies: [],
-      swiftSettings: [
-        .enableExperimentalFeature("StrictConcurrency")
-      ]
-    ),
-    .testTarget(
-      name: "ChessKitTests",
-      dependencies: ["ChessKit"]
-    )
+    .target(name: "ChessKit"),
+    .testTarget(name: "ChessKitTests", dependencies: ["ChessKit"])
   ]
 )

Sources/ChessKit/Board.swift

@@ -220,8 +220,10 @@ public struct Board: Sendable {
     let checkState = self.checkState(for: move.piece.color)
     processedMove.checkState = checkState
 
+    // draw by repetition
     positionHashCounts[position.hashValue, default: 0] += 1
 
+    // board state notification
     if checkState == .checkmate {
       delegate?.didEnd(with: .win(move.piece.color))
     } else if checkState == .stalemate {

Sources/ChessKit/Game.swift

@@ -10,7 +10,7 @@ import Foundation
 /// This object is the entry point for interacting with a full
 /// chess game within `ChessKit`. It provides methods for
 /// making moves and publishes the played moves in an observable way.
-public struct Game: Hashable {
+public struct Game: Hashable, Sendable {
 
   // MARK: - Properties
 

Sources/ChessKit/MoveTree/MoveTree+Index.swift

@@ -7,6 +7,7 @@ extension MoveTree {
   /// Object that represents the index of a node in the move tree.
   public struct Index: Hashable, Sendable {
 
+    /// Variation number corresponding to the main variation of the tree.
     public static let mainVariation = 0
 
     /// The move number.
@@ -86,6 +87,7 @@ extension MoveTree {
 
 }
 
+// MARK: - Comparable
 extension MoveTree.Index: Comparable {
   public static func < (lhs: Self, rhs: Self) -> Bool {
     if lhs.variation == rhs.variation {

Sources/ChessKit/MoveTree/MoveTree.swift

@@ -3,11 +3,13 @@
 //  ChessKit
 //
 
+import Foundation
+
 /// A tree-like data structure that represents the moves of a chess game.
 ///
 /// The tree maintains the move order including variations and
 /// provides index-based access for any element in the tree.
-public struct MoveTree: Hashable {
+public struct MoveTree: Hashable, Sendable {
 
   /// The index of the root of the move tree.
   ///
@@ -27,6 +29,10 @@ public struct MoveTree: Hashable {
     Array(dictionary.keys)
   }
 
+  /// Lock to restrict modification of tree nodes
+  /// to ensure `Sendable` conformance for ``Node``.
+  private static let nodeLock = NSLock()
+
   /// Adds a move to the move tree.
   ///
   /// - parameter move: The move to add to the tree.
@@ -67,7 +73,9 @@ public struct MoveTree: Hashable {
       }
     }
 
-    dictionary[newIndex] = newNode
+    Self.nodeLock.withLock {
+      dictionary[newIndex] = newNode
+    }
     newNode.index = newIndex
 
     if newIndex.variation == Index.mainVariation {
@@ -257,8 +265,10 @@ public struct MoveTree: Hashable {
     assessment: Move.Assessment = .null,
     comment: String = ""
   ) -> Move? {
-    dictionary[index]?.move.assessment = assessment
-    dictionary[index]?.move.comment = comment
+    Self.nodeLock.withLock {
+      dictionary[index]?.move.assessment = assessment
+      dictionary[index]?.move.comment = comment
+    }
     return dictionary[index]?.move
   }
 
@@ -343,7 +353,7 @@ extension MoveTree: Equatable {
 extension MoveTree {
 
   /// Object that represents a node in the move tree.
-  class Node: Hashable {
+  class Node: Hashable, @unchecked Sendable {
 
     /// The move for this node.
     var move: Move
@@ -365,7 +375,7 @@ extension MoveTree {
       lhs.index == rhs.index && lhs.move == rhs.move
     }
 
-    // MARK: - Hashable
+    // MARK: Hashable
     func hash(into hasher: inout Hasher) {
       hasher.combine(move)
       hasher.combine(index)

Tests/ChessKitTests/BoardTests.swift

@@ -34,7 +34,7 @@ final class BoardTests: XCTestCase {
     XCTAssertTrue(board.position.enPassantIsPossible)
   }
 
-  func testWhitePromotion() {
+  @MainActor func testWhitePromotion() {
     let pawn = Piece(.pawn, color: .white, square: .e7)
     let queen = Piece(.queen, color: .white, square: .e8)
     var board = Board(position: .init(pieces: [pawn]))
@@ -58,7 +58,7 @@ final class BoardTests: XCTestCase {
     XCTAssertEqual(promotionMove.end, .e8)
   }
 
-  func testBlackPromotion() {
+  @MainActor func testBlackPromotion() {
     let pawn = Piece(.pawn, color: .black, square: .e2)
     let queen = Piece(.queen, color: .black, square: .e1)
     var board = Board(position: .init(pieces: [pawn]))
@@ -82,7 +82,7 @@ final class BoardTests: XCTestCase {
     XCTAssertEqual(promotionMove.end, .e1)
   }
 
-  func testFiftyMoveRule() {
+  @MainActor func testFiftyMoveRule() {
     var board = Board(position: .fiftyMove)
     nonisolated(unsafe) var expectation: XCTestExpectation? = self.expectation(description: "Board returns fifty move draw result")
 
@@ -102,7 +102,7 @@ final class BoardTests: XCTestCase {
     waitForExpectations(timeout: 1.0)
   }
 
-  func testInsufficientMaterial() {
+  @MainActor func testInsufficientMaterial() {
     var board = Board(position: .init(fen: "k7/b6P/8/8/8/8/8/K7 w - - 0 1")!)
     nonisolated(unsafe) var expectation: XCTestExpectation? = self.expectation(description: "Board returns insufficient material draw result")
 
@@ -165,7 +165,7 @@ final class BoardTests: XCTestCase {
     XCTAssertTrue(board4.position.hasInsufficientMaterial)
   }
 
-  func testThreefoldRepetition() {
+  @MainActor func testThreefoldRepetition() {
     var board = Board(position: .standard)
 
     board.move(pieceAt: .e2, to: .e4)
@@ -350,7 +350,7 @@ final class BoardTests: XCTestCase {
     XCTAssertNil(move)
   }
 
-  func testCheckMove() {
+  @MainActor func testCheckMove() {
     var board = Board(position: .init(fen: "k7/7R/8/8/8/8/K7/8 w - - 0 1")!)
 
     nonisolated(unsafe) var expectation: XCTestExpectation? = self.expectation(description: "Board returns check result")
@@ -371,7 +371,7 @@ final class BoardTests: XCTestCase {
     waitForExpectations(timeout: 1.0)
   }
 
-  func testCheckmateMove() {
+  @MainActor func testCheckmateMove() {
     var board = Board(position: .init(fen: "k7/7R/6R1/8/8/8/K7/8 w - - 0 1")!)
 
     nonisolated(unsafe) var expectation: XCTestExpectation? = self.expectation(description: "Board returns checkmate result")

Tests/ChessKitTests/MoveTreeTests.swift

@@ -27,6 +27,13 @@ final class MoveTreeTests: XCTestCase {
     XCTAssertEqual(moveTree[.minimum.next], e4)
   }
 
+  func testNodeHashValue() {
+    var moveTree = MoveTree()
+    let e4 = Move(san: "e4", position: .standard)
+    moveTree[.minimum.next] = e4
+    XCTAssertNotNil(moveTree.dictionary[.minimum.next]?.hashValue)
+  }
+
   func testSameVariationComparability() {
     let wIndex = MoveTree.Index(number: 4, color: .white, variation: 2)
     XCTAssertLessThan(wIndex, wIndex.next)