Add JSClosure APIs to support specifying TaskExecutor and TaskPriority

Author: kateinoigakukun

Sources/JavaScriptKit/FundamentalObjects/JSClosure.swift

@@ -18,7 +18,7 @@ public protocol JSClosureProtocol: JSValueCompatible {
 public class JSOneshotClosure: JSObject, JSClosureProtocol {
     private var hostFuncRef: JavaScriptHostFuncRef = 0
 
-    public init(_ body: @escaping (sending [JSValue]) -> JSValue, file: String = #fileID, line: UInt32 = #line) {
+    public init(file: String = #fileID, line: UInt32 = #line, _ body: @escaping (sending [JSValue]) -> JSValue) {
         // 1. Fill `id` as zero at first to access `self` to get `ObjectIdentifier`.
         super.init(id: 0)
 
@@ -44,11 +44,34 @@ public class JSOneshotClosure: JSObject, JSClosureProtocol {
     }
 
     #if compiler(>=5.5) && (!hasFeature(Embedded) || os(WASI))
+    /// Creates a new `JSOneshotClosure` that calls the given Swift function asynchronously.
+    ///
+    /// - Parameters:
+    ///   - priority: The priority of the new unstructured Task created under the hood.
+    ///   - body: The Swift function to call asynchronously.
     @available(macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, *)
     public static func async(
+        priority: TaskPriority? = nil,
+        file: String = #fileID, line: UInt32 = #line,
         _ body: sending @escaping (sending [JSValue]) async throws(JSException) -> JSValue
     ) -> JSOneshotClosure {
-        JSOneshotClosure(makeAsyncClosure(body))
+        JSOneshotClosure(file: file, line: line, makeAsyncClosure(priority: priority, body))
+    }
+
+    /// Creates a new `JSOneshotClosure` that calls the given Swift function asynchronously.
+    ///
+    /// - Parameters:
+    ///   - taskExecutor: The executor preference of the new unstructured Task created under the hood.
+    ///   - priority: The priority of the new unstructured Task created under the hood.
+    ///   - body: The Swift function to call asynchronously.
+    @available(macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0, *)
+    public static func async(
+        executorPreference taskExecutor: (any TaskExecutor)? = nil,
+        priority: TaskPriority? = nil,
+        file: String = #fileID, line: UInt32 = #line,
+        _ body: @Sendable @escaping (sending [JSValue]) async throws(JSException) -> JSValue
+    ) -> JSOneshotClosure {
+        JSOneshotClosure(file: file, line: line, makeAsyncClosure(executorPreference: taskExecutor, priority: priority, body))
     }
     #endif
 
@@ -117,7 +140,7 @@ public class JSClosure: JSFunction, JSClosureProtocol {
         })
     }
 
-    public init(_ body: @escaping (sending [JSValue]) -> JSValue, file: String = #fileID, line: UInt32 = #line) {
+    public init(file: String = #fileID, line: UInt32 = #line, _ body: @escaping (sending [JSValue]) -> JSValue) {
         // 1. Fill `id` as zero at first to access `self` to get `ObjectIdentifier`.
         super.init(id: 0)
 
@@ -137,11 +160,34 @@ public class JSClosure: JSFunction, JSClosureProtocol {
     }
 
     #if compiler(>=5.5) && (!hasFeature(Embedded) || os(WASI))
+    /// Creates a new `JSClosure` that calls the given Swift function asynchronously.
+    ///
+    /// - Parameters:
+    ///   - priority: The priority of the new unstructured Task created under the hood.
+    ///   - body: The Swift function to call asynchronously.
     @available(macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, *)
     public static func async(
-        _ body: @Sendable @escaping (sending [JSValue]) async throws(JSException) -> JSValue
+        priority: TaskPriority? = nil,
+        file: String = #fileID, line: UInt32 = #line,
+        _ body: sending @escaping @isolated(any) (sending [JSValue]) async throws(JSException) -> JSValue
+    ) -> JSClosure {
+        JSClosure(file: file, line: line, makeAsyncClosure(priority: priority, body))
+    }
+
+    /// Creates a new `JSClosure` that calls the given Swift function asynchronously.
+    ///
+    /// - Parameters:
+    ///   - taskExecutor: The executor preference of the new unstructured Task created under the hood.
+    ///   - priority: The priority of the new unstructured Task created under the hood.
+    ///   - body: The Swift function to call asynchronously.
+    @available(macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0, *)
+    public static func async(
+        executorPreference taskExecutor: (any TaskExecutor)? = nil,
+        priority: TaskPriority? = nil,
+        file: String = #fileID, line: UInt32 = #line,
+        _ body: sending @escaping (sending [JSValue]) async throws(JSException) -> JSValue
     ) -> JSClosure {
-        JSClosure(makeAsyncClosure(body))
+        JSClosure(file: file, line: line, makeAsyncClosure(executorPreference: taskExecutor, priority: priority, body))
     }
     #endif
 
@@ -157,6 +203,36 @@ public class JSClosure: JSFunction, JSClosureProtocol {
 #if compiler(>=5.5) && (!hasFeature(Embedded) || os(WASI))
 @available(macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, *)
 private func makeAsyncClosure(
+    priority: TaskPriority?,
+    _ body: sending @escaping @isolated(any) (sending [JSValue]) async throws(JSException) -> JSValue
+) -> ((sending [JSValue]) -> JSValue) {
+    { arguments in
+        JSPromise { resolver in
+            // NOTE: The context is fully transferred to the unstructured task
+            // isolation but the compiler can't prove it yet, so we need to
+            // use `@unchecked Sendable` to make it compile with the Swift 6 mode.
+            struct Context: @unchecked Sendable {
+                let resolver: (JSPromise.Result) -> Void
+                let arguments: [JSValue]
+                let body: (sending [JSValue]) async throws(JSException) -> JSValue
+            }
+            let context = Context(resolver: resolver, arguments: arguments, body: body)
+            Task(priority: priority) {
+                do throws(JSException) {
+                    let result = try await context.body(context.arguments)
+                    context.resolver(.success(result))
+                } catch {
+                    context.resolver(.failure(error.thrownValue))
+                }
+            }
+        }.jsValue()
+    }
+}
+
+@available(macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0, *)
+private func makeAsyncClosure(
+    executorPreference taskExecutor: (any TaskExecutor)?,
+    priority: TaskPriority?,
     _ body: sending @escaping (sending [JSValue]) async throws(JSException) -> JSValue
 ) -> ((sending [JSValue]) -> JSValue) {
     { arguments in
@@ -170,7 +246,7 @@ private func makeAsyncClosure(
                 let body: (sending [JSValue]) async throws(JSException) -> JSValue
             }
             let context = Context(resolver: resolver, arguments: arguments, body: body)
-            Task {
+            Task(executorPreference: taskExecutor, priority: priority) {
                 do throws(JSException) {
                     let result = try await context.body(context.arguments)
                     context.resolver(.success(result))