Add speculative concurrency bug workaround.

Author: jaredsinclair

Sources/ImageCache/FileNameHashes.swift

@@ -0,0 +1,28 @@
+//
+//  FileNameHashes.swift
+//  ImageCache
+//
+//  Created by Jared Sinclair on 11/10/24.
+//
+
+import Foundation
+import Etcetera
+import CryptoKit
+
+public enum FileNameHashes {
+
+    /// Your app can provide something stronger than the default implementation
+    /// (a string representation of a SHA1 hash) if so desired.
+    public static func registerFileNameHasher(block: @escaping (URL) -> String) {
+        _uniqueFilenameFromUrl.access {
+            $0 = block
+        }
+    }
+
+    static func uniqueFilename(from url: URL) -> String {
+        _uniqueFilenameFromUrl.current(url)
+    }
+
+    private static let _uniqueFilenameFromUrl: Protected<(URL) -> String> = Protected(Insecure.SHA1.filename(for:))
+
+}

Sources/ImageCache/ImageCache.swift

@@ -10,7 +10,6 @@
 // swiftlint:disable nesting - Seriously, why do we even Swift then.
 // swiftlint:disable function_parameter_count - Some problems are hard.
 
-import CryptoKit
 import Etcetera
 import Combine
 
@@ -48,13 +47,6 @@ import AppKit
         didSet { trimStaleFiles() }
     }
 
-    /// Your app can provide something stronger than the default implementation
-    /// (a string representation of a SHA1 hash) if so desired.
-    public nonisolated var uniqueFilenameFromUrl: (URL) -> String {
-        get { _uniqueFilenameFromUrl.current }
-        set { _uniqueFilenameFromUrl.current = newValue }
-    }
-
     /// When `true` this will empty the in-memory cache when the app enters the
     /// background. This can help reduce the likelihood that your app will be
     /// terminated in order to reclaim memory for foregrounded applications.
@@ -75,7 +67,6 @@ import AppKit
     private let formattingQueue: OperationQueue
     private let diskWritingQueue: OperationQueue
     private let workQueue: OperationQueue
-    private nonisolated let _uniqueFilenameFromUrl: Protected<(URL) -> String>
     private var cancellables = Set<AnyCancellable>()
 
     // MARK: Init / Deinit
@@ -94,7 +85,6 @@ import AppKit
         directory: URL = ImageCache.defaultDirectory,
         byteLimitForFileStorage: Bytes? = .fromMegabytes(500)
     ) {
-        self._uniqueFilenameFromUrl = Protected(Insecure.SHA1.filename(for:))
         self.directory = directory
         self.byteLimitForFileStorage = byteLimitForFileStorage
         self.urlSession = {
@@ -543,7 +533,7 @@ import AppKit
         switch key.source {
         case .url(let url):
             let originalKey = ImageKey(source: .url(url), format: .original)
-            filename = uniqueFilenameFromUrl(url) + originalKey.filenameSuffix
+            filename = FileNameHashes.uniqueFilename(from: url) + originalKey.filenameSuffix
         case .manuallySeeded(let id):
             filename = "\(id).MANUALLY_SEEDED_ORIGINAL"
         case .custom(let id, let namespace, _):
@@ -558,7 +548,7 @@ import AppKit
         let filename: String
         switch key.source {
         case .url(let url):
-            filename = uniqueFilenameFromUrl(url) + key.filenameSuffix
+            filename = FileNameHashes.uniqueFilename(from: url) + key.filenameSuffix
         case .manuallySeeded(let id):
             filename = "\(id).\(key.filenameSuffix)"
         case .custom(let identifier, let namespace, _):