Fix Swift concurrency (#722)

* fix actor isolation
* fix tests

Parchment/Classes/PageViewCoordinator.swift

@@ -1,6 +1,7 @@
 import UIKit
 
 @available(iOS 14.0, *)
+@MainActor
 final class PageViewCoordinator: PagingViewControllerDataSource, PagingViewControllerDelegate {
     final class WeakReference<T: AnyObject> {
         weak var value: T?

Parchment/Classes/PageViewManager.swift

@@ -1,5 +1,6 @@
 import UIKit
 
+@MainActor
 final class PageViewManager {
     weak var dataSource: PageViewManagerDataSource?
     weak var delegate: PageViewManagerDelegate?

Parchment/Classes/PagingController.swift

@@ -1,6 +1,7 @@
 import UIKit
 
 protocol PagingControllerSizeDelegate: AnyObject {
+    @MainActor
     func width(for: PagingItem, isSelected: Bool) -> CGFloat
 }
 

Parchment/Classes/PagingStaticDataSource.swift

@@ -1,7 +1,8 @@
 import Foundation
 import UIKit
 
-class PagingStaticDataSource: PagingViewControllerInfiniteDataSource {
+@MainActor
+final class PagingStaticDataSource: PagingViewControllerInfiniteDataSource {
     private(set) var items: [PagingItem] = []
     private let viewControllers: [UIViewController]
 

Parchment/Enums/InvalidationState.swift

@@ -6,6 +6,7 @@ import UIKit
 /// called and we can use we can use this to determine exactly how
 /// much we need to invalidate by adding together the states each
 /// time a new context is invalidated.
+@MainActor
 public enum InvalidationState {
     case nothing
     case everything

Parchment/Protocols/CollectionView.swift

@@ -1,5 +1,6 @@
 import UIKit
 
+@MainActor
 protocol CollectionViewLayout: AnyObject {
     var state: PagingState { get set }
     var visibleItems: PagingItems { get set }
@@ -13,6 +14,7 @@ protocol CollectionViewLayout: AnyObject {
 
 extension PagingCollectionViewLayout: CollectionViewLayout {}
 
+@MainActor
 protocol CollectionView: AnyObject {
     var indexPathsForVisibleItems: [IndexPath] { get }
     var isDragging: Bool { get }

Parchment/Protocols/PageViewControllerDataSource.swift

@@ -8,6 +8,7 @@ public protocol PageViewControllerDataSource: AnyObject {
     /// - Parameters:
     ///   - pageViewController: The `PageViewController` instance.
     ///   - viewController: The current view controller.
+    @MainActor
     func pageViewController(
         _ pageViewController: PageViewController,
         viewControllerBeforeViewController viewController: UIViewController
@@ -18,6 +19,7 @@ public protocol PageViewControllerDataSource: AnyObject {
     /// - Parameters:
     ///   - pageViewController: The `PageViewController` instance.
     ///   - viewController: The current view controller.
+    @MainActor
     func pageViewController(
         _ pageViewController: PageViewController,
         viewControllerAfterViewController viewController: UIViewController

Parchment/Protocols/PageViewControllerDelegate.swift

@@ -13,6 +13,7 @@ public protocol PageViewControllerDelegate: AnyObject {
     ///   scrolling from.
     ///   - destinationViewController: The view controller the user is
     ///   scrolling towards.
+    @MainActor
     func pageViewController(
         _ pageViewController: PageViewController,
         willStartScrollingFrom startingViewController: UIViewController,
@@ -30,6 +31,7 @@ public protocol PageViewControllerDelegate: AnyObject {
     ///   towards one of the edges.
     ///   - progress: The progress of the scroll transition. Between 0
     ///   and 1.
+    @MainActor
     func pageViewController(
         _ pageViewController: PageViewController,
         isScrollingFrom startingViewController: UIViewController,
@@ -47,6 +49,7 @@ public protocol PageViewControllerDelegate: AnyObject {
     ///   scrolling towards.
     ///   - transitionSuccessful: A boolean indicating whether the
     ///   transition completed, or was cancelled by the user.
+    @MainActor
     func pageViewController(
         _ pageViewController: PageViewController,
         didFinishScrollingFrom startingViewController: UIViewController,

Parchment/Protocols/PageViewManagerDataSource.swift

@@ -1,5 +1,6 @@
 import UIKit
 
+@MainActor
 protocol PageViewManagerDataSource: AnyObject {
     func viewControllerBefore(_ viewController: UIViewController) -> UIViewController?
     func viewControllerAfter(_ viewController: UIViewController) -> UIViewController?

Parchment/Protocols/PageViewManagerDelegate.swift

@@ -1,5 +1,6 @@
 import UIKit
 
+@MainActor
 protocol PageViewManagerDelegate: AnyObject {
     func scrollForward()
     func scrollReverse()

Parchment/Protocols/PagingLayout.swift

@@ -3,9 +3,11 @@ import Foundation
 /// Used to be able to initialize a layout based on the type defined
 /// in the menuLayoutClass property.
 protocol PagingLayout {
+    @MainActor
     init()
 }
 
+@MainActor
 func createLayout<T>(layout: T.Type) -> T where T: PagingLayout {
     return layout.init()
 }

Parchment/Protocols/PagingMenuDataSource.swift

@@ -1,6 +1,8 @@
 import Foundation
 
 public protocol PagingMenuDataSource: AnyObject {
+    @MainActor
     func pagingItemBefore(pagingItem: PagingItem) -> PagingItem?
+    @MainActor
     func pagingItemAfter(pagingItem: PagingItem) -> PagingItem?
 }

Parchment/Protocols/PagingMenuDelegate.swift

@@ -1,6 +1,8 @@
 import Foundation
 
 public protocol PagingMenuDelegate: AnyObject {
+    @MainActor
     func selectContent(pagingItem: PagingItem, direction: PagingDirection, animated: Bool)
+    @MainActor
     func removeContent()
 }

Parchment/Protocols/PagingViewControllerDataSource.swift

@@ -14,6 +14,7 @@ public protocol PagingViewControllerDataSource: AnyObject {
     /// - Parameter pagingViewController: The `PagingViewController`
     /// instance
     /// - Returns: The number of view controllers
+    @MainActor
     func numberOfViewControllers(in pagingViewController: PagingViewController) -> Int
 
     /// Return the view controller accociated with a given index. This
@@ -24,12 +25,14 @@ public protocol PagingViewControllerDataSource: AnyObject {
     /// instance
     /// - Parameter index: The index of a given `PagingItem`
     /// - Returns: The view controller for the given index
+    @MainActor
     func pagingViewController(_: PagingViewController, viewControllerAt index: Int) -> UIViewController
 
     /// Return the `PagingItem` instance for a given index
     ///
     /// - Parameter pagingViewController: The `PagingViewController`
     /// instance
     /// - Returns: The `PagingItem` instance
+    @MainActor
     func pagingViewController(_: PagingViewController, pagingItemAt index: Int) -> PagingItem
 }

Parchment/Protocols/PagingViewControllerDelegate.swift

@@ -14,6 +14,7 @@ public protocol PagingViewControllerDelegate: AnyObject {
     /// - Parameter destinationViewController: The view controller for
     /// the upcoming paging item
     /// - Parameter progress: The progress of the scroll transition
+    @MainActor
     func pagingViewController(
         _: PagingViewController,
         isScrollingFromItem currentPagingItem: PagingItem,
@@ -30,6 +31,7 @@ public protocol PagingViewControllerDelegate: AnyObject {
     /// current paging item
     /// - Parameter destinationViewController: The view controller for
     /// the upcoming paging item
+    @MainActor
     func pagingViewController(
         _: PagingViewController,
         willScrollToItem pagingItem: PagingItem,
@@ -46,6 +48,7 @@ public protocol PagingViewControllerDelegate: AnyObject {
     /// the upcoming paging item
     /// - Parameter transitionSuccessful: Boolean that indicates whether
     /// the transition to the paging item was successful or not
+    @MainActor
     func pagingViewController(
         _ pagingViewController: PagingViewController,
         didScrollToItem pagingItem: PagingItem,
@@ -58,6 +61,7 @@ public protocol PagingViewControllerDelegate: AnyObject {
     ///
     /// - Parameter pagingViewController: The `PagingViewController` instance
     /// - Parameter pagingItem: The item that was selected.
+    @MainActor
     func pagingViewController(
         _ pagingViewController: PagingViewController,
         didSelectItem pagingItem: PagingItem

Parchment/Protocols/PagingViewControllerInfiniteDataSource.swift

@@ -16,6 +16,7 @@ public protocol PagingViewControllerInfiniteDataSource: AnyObject {
     /// instance
     /// - Parameter viewControllerForPagingItem: A `PagingItem` instance
     /// - Returns: The view controller for the `PagingItem` instance
+    @MainActor
     func pagingViewController(_: PagingViewController, viewControllerFor pagingItem: PagingItem) -> UIViewController
 
     /// The `PagingItem` that comes before a given `PagingItem`
@@ -26,6 +27,7 @@ public protocol PagingViewControllerInfiniteDataSource: AnyObject {
     /// - Returns: The `PagingItem` that appears before the given
     /// `PagingItem`, or `nil` to indicate that no more progress can be
     /// made in that direction.
+    @MainActor
     func pagingViewController(_: PagingViewController, itemBefore pagingItem: PagingItem) -> PagingItem?
 
     /// The `PagingItem` that comes after a given `PagingItem`
@@ -36,5 +38,6 @@ public protocol PagingViewControllerInfiniteDataSource: AnyObject {
     /// - Returns: The `PagingItem` that appears after the given
     /// `PagingItem`, or `nil` to indicate that no more progress can be
     /// made in that direction.
+    @MainActor
     func pagingViewController(_: PagingViewController, itemAfter pagingItem: PagingItem) -> PagingItem?
 }

Parchment/Structs/Page.swift

@@ -25,6 +25,7 @@ import SwiftUI
 /// initializers are closures that return the view hierarchy for
 /// the header and body of the page, respectively.
 @available(iOS 14.0, *)
+@MainActor
 public struct Page {
     let reuseIdentifier: String
     let pageIdentifier: String?

Parchment/Structs/PagingDistance.swift

@@ -1,6 +1,7 @@
 import Foundation
 import UIKit
 
+@MainActor
 struct PagingDistance {
     private let view: CollectionView
     private let hasItemsBefore: Bool

ParchmentTests/PageViewManagerTests.swift

@@ -2,6 +2,7 @@ import Foundation
 @testable import Parchment
 import XCTest
 
+@MainActor
 final class PageViewManagerTests: XCTestCase {
     var dataSource: MockPageViewManagerDataSource!
     var delegate: MockPageViewManagerDelegate!

ParchmentTests/PagingCollectionViewLayoutTests.swift

@@ -2,6 +2,7 @@
 import UIKit
 import XCTest
 
+@MainActor
 final class PagingCollectionViewLayoutTests: XCTestCase {
     private var window: UIWindow!
     private var options: PagingOptions!

ParchmentTests/PagingDistanceCenteredTests.swift

@@ -1,6 +1,7 @@
 @testable import Parchment
 import XCTest
 
+@MainActor
 final class PagingDistanceCenteredTests: XCTestCase {
     private var sizeCache: PagingSizeCache!
 

ParchmentTests/PagingDistanceLeftTests.swift

@@ -1,6 +1,7 @@
 @testable import Parchment
 import XCTest
 
+@MainActor
 final class PagingDistanceLeftTests: XCTestCase {
     private var sizeCache: PagingSizeCache!
 

ParchmentTests/PagingDistanceRightTests.swift

@@ -1,6 +1,7 @@
 @testable import Parchment
 import XCTest
 
+@MainActor
 final class PagingDistanceRightTests: XCTestCase {
     private var sizeCache: PagingSizeCache!
 

ParchmentTests/Utilities/CreateDistance.swift

@@ -1,6 +1,7 @@
 import Foundation
 @testable import Parchment
 
+@MainActor
 func createDistance(
     bounds: CGRect = .zero,
     contentSize: CGSize? = nil,