LibJS: Add console.trace()

Author: https://github.com/linusg
Commit: https://github.com/SerenityOS/serenity/commit/3b21c4aa567
Pull-request: https://github.com/SerenityOS/serenity/pull/1742

Libraries/LibJS/Interpreter.h

@@ -112,6 +112,7 @@ public:
     }
     void pop_call_frame() { m_call_stack.take_last(); }
     const CallFrame& call_frame() { return m_call_stack.last(); }
+    const Vector<CallFrame> call_stack() { return m_call_stack; }
 
     size_t argument_count() const
     {

Libraries/LibJS/Runtime/ConsoleObject.cpp

@@ -35,6 +35,7 @@ namespace JS {
 ConsoleObject::ConsoleObject()
 {
     put_native_function("log", log);
+    put_native_function("trace", trace);
 }
 
 ConsoleObject::~ConsoleObject()
@@ -52,4 +53,18 @@ Value ConsoleObject::log(Interpreter& interpreter)
     return js_undefined();
 }
 
+Value ConsoleObject::trace(Interpreter& interpreter)
+{
+    log(interpreter);
+    auto call_stack = interpreter.call_stack();
+    // -2 to skip the console.trace() call frame
+    for (ssize_t i = call_stack.size() - 2; i >= 0; --i) {
+        auto function_name = call_stack[i].function_name;
+        if (String(function_name).is_empty())
+            function_name = "<anonymous>";
+        printf("%s\n", function_name.characters());
+    }
+    return js_undefined();
+}
+
 }

Libraries/LibJS/Runtime/ConsoleObject.h

@@ -39,6 +39,7 @@ private:
     virtual const char* class_name() const override { return "ConsoleObject"; }
 
     static Value log(Interpreter&);
+    static Value trace(Interpreter&);
 };
 
 }