Applied the review feedback: hooked tracing to the “Tracing” trait and removed the extra compdef, made JSClosure tracing use String file IDs, and avoided unknown placeholders for method names by allowing nil method names.

- Updated trait name and removed redundant define; tracing is now gated by trait “Tracing” and uses `#if Tracing` (`Package.swift`).
- Hooks now accept optional method names and closure file IDs as `String`, with all tracing conditionals using the trait flag (`Sources/JavaScriptKit/JSTracing.swift`, `Sources/JavaScriptKit/FundamentalObjects/JSObject+CallAsFunction.swift`, `Sources/JavaScriptKit/FundamentalObjects/JSThrowingFunction.swift`, `Sources/JavaScriptKit/FundamentalObjects/JSClosure.swift`, `Sources/JavaScriptKit/FundamentalObjects/JSObject.swift`).
- Documentation updated to instruct enabling tracing via `--traits Tracing` (`Sources/JavaScriptKit/Documentation.docc/Articles/Debugging.md`).

Tests not run. Suggest running `swift build --traits Tracing` to verify the tracing variant compiles.

Author: kateinoigakukun

Package.swift

@@ -9,7 +9,7 @@ let useLegacyResourceBundling =
     Context.environment["JAVASCRIPTKIT_USE_LEGACY_RESOURCE_BUNDLING"].flatMap(Bool.init) ?? false
 
 let tracingTrait = Trait(
-    name: "JavaScriptKitTracing",
+    name: "Tracing",
     description: "Enable opt-in Swift <-> JavaScript bridge tracing hooks.",
     enabledTraits: []
 )
@@ -57,8 +57,7 @@ let package = Package(
                     .unsafeFlags(["-fdeclspec"])
                 ] : nil,
             swiftSettings: [
-                .enableExperimentalFeature("Extern"),
-                .define("JAVASCRIPTKIT_ENABLE_TRACING", .when(traits: ["JavaScriptKitTracing"])),
+                .enableExperimentalFeature("Extern")
             ]
                 + (shouldBuildForEmbedded
                     ? [

Sources/JavaScriptKit/Documentation.docc/Articles/Debugging.md

@@ -60,10 +60,10 @@ See [the DevTools team's official introduction](https://developer.chrome.com/blo
 
 ## Bridge Call Tracing
 
-Enable the `JavaScriptKitTracing` package trait to compile lightweight hook points for Swift <-> JavaScript calls. Tracing is off by default and adds no runtime overhead unless the trait is enabled:
+Enable the `Tracing` package trait to compile lightweight hook points for Swift <-> JavaScript calls. Tracing is off by default and adds no runtime overhead unless the trait is enabled:
 
 ```bash
-swift build --traits JavaScriptKitTracing
+swift build --traits Tracing
 ```
 
 The hooks are invoked at the start and end of each bridge crossing without collecting data for you. For example:

Sources/JavaScriptKit/FundamentalObjects/JSClosure.swift

@@ -19,7 +19,7 @@ public class JSOneshotClosure: JSObject, JSClosureProtocol {
     private var hostFuncRef: JavaScriptHostFuncRef = 0
 
     public init(
-        file: StaticString = #fileID,
+        file: String = #fileID,
         line: UInt32 = #line,
         _ body: @escaping (sending [JSValue]) -> JSValue
     ) {
@@ -28,7 +28,7 @@ public class JSOneshotClosure: JSObject, JSClosureProtocol {
 
         // 2. Create a new JavaScript function which calls the given Swift function.
         hostFuncRef = JavaScriptHostFuncRef(bitPattern: ObjectIdentifier(self))
-        _id = withExtendedLifetime(JSString(String(file))) { file in
+        _id = withExtendedLifetime(JSString(file)) { file in
             swjs_create_oneshot_function(hostFuncRef, line, file.asInternalJSRef())
         }
 
@@ -60,7 +60,7 @@ public class JSOneshotClosure: JSObject, JSClosureProtocol {
     @available(macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, *)
     public static func async(
         priority: TaskPriority? = nil,
-        file: StaticString = #fileID,
+        file: String = #fileID,
         line: UInt32 = #line,
         _ body: @escaping (sending [JSValue]) async throws(JSException) -> JSValue
     ) -> JSOneshotClosure {
@@ -79,7 +79,7 @@ public class JSOneshotClosure: JSObject, JSClosureProtocol {
     public static func async(
         executorPreference taskExecutor: (any TaskExecutor)? = nil,
         priority: TaskPriority? = nil,
-        file: StaticString = #fileID,
+        file: String = #fileID,
         line: UInt32 = #line,
         _ body: @escaping (sending [JSValue]) async throws(JSException) -> JSValue
     ) -> JSOneshotClosure {
@@ -122,7 +122,7 @@ public class JSClosure: JSObject, JSClosureProtocol {
         struct Entry {
             let object: JSObject
             let body: (sending [JSValue]) -> JSValue
-            let fileID: StaticString
+            let fileID: String
             let line: UInt32
         }
         private var storage: [JavaScriptHostFuncRef: Entry] = [:]
@@ -160,7 +160,7 @@ public class JSClosure: JSObject, JSClosureProtocol {
     }
 
     public init(
-        file: StaticString = #fileID,
+        file: String = #fileID,
         line: UInt32 = #line,
         _ body: @escaping (sending [JSValue]) -> JSValue
     ) {
@@ -169,7 +169,7 @@ public class JSClosure: JSObject, JSClosureProtocol {
 
         // 2. Create a new JavaScript function which calls the given Swift function.
         hostFuncRef = JavaScriptHostFuncRef(bitPattern: ObjectIdentifier(self))
-        _id = withExtendedLifetime(JSString(String(file))) { file in
+        _id = withExtendedLifetime(JSString(file)) { file in
             swjs_create_function(hostFuncRef, line, file.asInternalJSRef())
         }
 
@@ -198,7 +198,7 @@ public class JSClosure: JSObject, JSClosureProtocol {
     @available(macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, *)
     public static func async(
         priority: TaskPriority? = nil,
-        file: StaticString = #fileID,
+        file: String = #fileID,
         line: UInt32 = #line,
         _ body: @escaping @isolated(any) (sending [JSValue]) async throws(JSException) -> JSValue
     ) -> JSClosure {
@@ -217,7 +217,7 @@ public class JSClosure: JSObject, JSClosureProtocol {
     public static func async(
         executorPreference taskExecutor: (any TaskExecutor)? = nil,
         priority: TaskPriority? = nil,
-        file: StaticString = #fileID,
+        file: String = #fileID,
         line: UInt32 = #line,
         _ body: @escaping (sending [JSValue]) async throws(JSException) -> JSValue
     ) -> JSClosure {
@@ -338,7 +338,7 @@ func _call_host_function_impl(
     guard let entry = JSClosure.sharedClosures.wrappedValue[hostFuncRef] else {
         return true
     }
-#if JAVASCRIPTKIT_ENABLE_TRACING
+#if Tracing
     let traceEnd = JSTracingHooks.beginJSClosureCall(
         JSTracing.JSClosureCallInfo(fileID: entry.fileID, line: UInt(entry.line))
     )
@@ -347,7 +347,7 @@ func _call_host_function_impl(
     for i in 0..<Int(argc) {
         arguments.append(argv[i].jsValue)
     }
-#if JAVASCRIPTKIT_ENABLE_TRACING
+#if Tracing
     defer { traceEnd?() }
 #endif
     let result = entry.body(arguments)

Sources/JavaScriptKit/FundamentalObjects/JSObject+CallAsFunction.swift

@@ -52,7 +52,7 @@ extension JSObject {
     /// - Parameter arguments: Arguments to be passed to this constructor function.
     /// - Returns: A new instance of this constructor.
     public func new(arguments: [ConvertibleToJSValue]) -> JSObject {
-        #if JAVASCRIPTKIT_ENABLE_TRACING
+        #if Tracing
         let jsValues = arguments.map { $0.jsValue }
         return new(arguments: jsValues)
         #else
@@ -105,7 +105,7 @@ extension JSObject {
     /// - Parameter arguments: Arguments to be passed to this constructor function.
     /// - Returns: A new instance of this constructor.
     public func new(arguments: [JSValue]) -> JSObject {
-        #if JAVASCRIPTKIT_ENABLE_TRACING
+        #if Tracing
         let traceEnd = JSTracingHooks.beginJSCall(.function(function: self, arguments: arguments))
         defer { traceEnd?() }
         #endif
@@ -122,11 +122,11 @@ extension JSObject {
     }
 
     final func invokeNonThrowingJSFunction(arguments: [JSValue]) -> RawJSValue {
-        #if JAVASCRIPTKIT_ENABLE_TRACING
+        #if Tracing
         let traceEnd = JSTracingHooks.beginJSCall(.function(function: self, arguments: arguments))
         #endif
         let result = arguments.withRawJSValues { invokeNonThrowingJSFunction(rawValues: $0) }
-        #if JAVASCRIPTKIT_ENABLE_TRACING
+        #if Tracing
         traceEnd?()
         #endif
         return result
@@ -135,17 +135,13 @@ extension JSObject {
     final func invokeNonThrowingJSFunction(
         arguments: [JSValue],
         this: JSObject
-        #if JAVASCRIPTKIT_ENABLE_TRACING
+        #if Tracing
         , tracedMethodName: String? = nil
         #endif
     ) -> RawJSValue {
-        #if JAVASCRIPTKIT_ENABLE_TRACING
+        #if Tracing
         let traceEnd = JSTracingHooks.beginJSCall(
-            .method(
-                receiver: this,
-                methodName: tracedMethodName ?? "<unknown>",
-                arguments: arguments
-            )
+            .method(receiver: this, methodName: tracedMethodName, arguments: arguments)
         )
         #endif
         let result = arguments.withRawJSValues {
@@ -154,15 +150,15 @@ extension JSObject {
                 this: this
             )
         }
-        #if JAVASCRIPTKIT_ENABLE_TRACING
+        #if Tracing
         traceEnd?()
         #endif
         return result
     }
 
     #if !hasFeature(Embedded)
     final func invokeNonThrowingJSFunction(arguments: [ConvertibleToJSValue]) -> RawJSValue {
-        #if JAVASCRIPTKIT_ENABLE_TRACING
+        #if Tracing
         let jsValues = arguments.map { $0.jsValue }
         return invokeNonThrowingJSFunction(arguments: jsValues)
         #else
@@ -173,11 +169,11 @@ extension JSObject {
     final func invokeNonThrowingJSFunction(
         arguments: [ConvertibleToJSValue],
         this: JSObject
-        #if JAVASCRIPTKIT_ENABLE_TRACING
+        #if Tracing
         , tracedMethodName: String? = nil
         #endif
     ) -> RawJSValue {
-        #if JAVASCRIPTKIT_ENABLE_TRACING
+        #if Tracing
         let jsValues = arguments.map { $0.jsValue }
         return invokeNonThrowingJSFunction(
             arguments: jsValues,

Sources/JavaScriptKit/FundamentalObjects/JSObject.swift

@@ -94,7 +94,7 @@ public class JSObject: Equatable, ExpressibleByDictionaryLiteral {
     public subscript(_ name: String) -> ((ConvertibleToJSValue...) -> JSValue)? {
         guard let function = self[name].function else { return nil }
         return { (arguments: ConvertibleToJSValue...) in
-            #if JAVASCRIPTKIT_ENABLE_TRACING
+            #if Tracing
             return function.invokeNonThrowingJSFunction(
                 arguments: arguments,
                 this: self,
@@ -120,7 +120,7 @@ public class JSObject: Equatable, ExpressibleByDictionaryLiteral {
     public subscript(_ name: JSString) -> ((ConvertibleToJSValue...) -> JSValue)? {
         guard let function = self[name].function else { return nil }
         return { (arguments: ConvertibleToJSValue...) in
-            #if JAVASCRIPTKIT_ENABLE_TRACING
+            #if Tracing
             return function.invokeNonThrowingJSFunction(
                 arguments: arguments,
                 this: self,

Sources/JavaScriptKit/FundamentalObjects/JSThrowingFunction.swift

@@ -77,11 +77,11 @@ private func invokeJSFunction(
     arguments: [ConvertibleToJSValue],
     this: JSObject?
 ) throws -> JSValue {
-    #if JAVASCRIPTKIT_ENABLE_TRACING
+    #if Tracing
     let jsValues = arguments.map { $0.jsValue }
     let traceEnd = JSTracingHooks.beginJSCall(
         this.map {
-            .method(receiver: $0, methodName: "<unknown>", arguments: jsValues)
+            .method(receiver: $0, methodName: nil, arguments: jsValues)
         } ?? .function(function: jsFunc, arguments: jsValues)
     )
     defer { traceEnd?() }

Sources/JavaScriptKit/JSTracing.swift

@@ -1,12 +1,12 @@
-#if JAVASCRIPTKIT_ENABLE_TRACING
+#if Tracing
 
 /// Hooks for tracing Swift <-> JavaScript bridge calls.
 public struct JSTracing {
     public static let `default` = JSTracing()
 
     public enum JSCallInfo {
         case function(function: JSObject, arguments: [JSValue])
-        case method(receiver: JSObject, methodName: String, arguments: [JSValue])
+        case method(receiver: JSObject, methodName: String?, arguments: [JSValue])
     }
 
     /// Register a hook for Swift to JavaScript calls.
@@ -24,7 +24,7 @@ public struct JSTracing {
 
     public struct JSClosureCallInfo {
         /// The file identifier where the called `JSClosure` was created.
-        public let fileID: StaticString
+        public let fileID: String
         /// The line number where the called `JSClosure` was created.
         public let line: UInt
     }