Turn StylesheetCache into a thread-safe actor (#1461)

* Turn `StylesheetCache` into a thread-safe actor

Fixes #1460

* Update Changelog

Author: nighthawk

CHANGELOG.md

@@ -20,6 +20,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Updates to change-tracked properties no longer occur on the next RunLoop, fixing modal dismissal on macOS (#1450)
 - `+` characters are properly encoded as `%2B` in form events (#1449)
 - Fixed retain cycle in `LiveViewCoordinator` (#1455)
+- Made `StylesheetCache` thread-safe, fixing occasional crashes (#1461)
 
 ## [0.3.0] 2024-08-21
 

Sources/LiveViewNative/Coordinators/LiveSessionCoordinator.swift

@@ -229,14 +229,14 @@ public class LiveSessionCoordinator<R: RootRegistry>: ObservableObject {
                     guard let url = URL(string: try style.attr("url"), relativeTo: url)
                     else { continue }
                     group.addTask {
-                        if let cachedStylesheet = StylesheetCache[for: url, registry: R.self] {
+                        if let cachedStylesheet = await StylesheetCache.shared.read(for: url, registry: R.self) {
                             return cachedStylesheet
                         } else {
-                            let (data, response) = try await self.urlSession.data(from: url)
+                            let (data, _) = try await self.urlSession.data(from: url)
                             guard let contents = String(data: data, encoding: .utf8)
                             else { return Stylesheet<R>(content: [], classes: [:]) }
                             let stylesheet = try Stylesheet<R>(from: contents, in: .init())
-                            StylesheetCache[for: url, registry: R.self] = stylesheet
+                            await StylesheetCache.shared.write(stylesheet, for: url, registry: R.self)
                             return stylesheet
                         }
                     }
@@ -513,7 +513,7 @@ public class LiveSessionCoordinator<R: RootRegistry>: ObservableObject {
         self.liveReloadChannel!.on("assets_change") { [weak self] _ in
             logger.debug("[LiveReload] assets changed, reloading")
             Task {
-                StylesheetCache.removeAll()
+                await StylesheetCache.shared.removeAll()
                 // need to fully reconnect (rather than just re-join channel) because the elixir code reloader only triggers on http reqs
                 await self?.reconnect()
             }

Sources/LiveViewNative/Stylesheets/Stylesheet.swift

@@ -27,19 +27,20 @@ public struct Stylesheet<R: RootRegistry> {
     }
 }
 
-enum StylesheetCache {
-    private static var cache = [URL:Any]()
+actor StylesheetCache {
+    static let shared = StylesheetCache()
 
-    static subscript<R: RootRegistry>(for url: URL, registry _: R.Type = R.self) -> Stylesheet<R>? {
-        get {
-            Self.cache[url.absoluteURL] as? Stylesheet<R>
-        }
-        set {
-            Self.cache[url.absoluteURL] = newValue as Any
-        }
+    private var cache = [URL:Any]()
+    
+    func read<R: RootRegistry>(for url: URL, registry _: R.Type = R.self) -> Stylesheet<R>? {
+        cache[url.absoluteURL] as? Stylesheet<R>
+    }
+
+    func write<R: RootRegistry>(_ value: Stylesheet<R>, for url: URL, registry _: R.Type = R.self) {
+        cache[url.absoluteURL] = value
     }
 
-    static func removeAll() {
+    func removeAll() {
         cache.removeAll()
     }
 }