NativeReflect: fix Reflect.construct() with LambdaConstructor

Author: duonglaiquang

rhino/src/main/java/org/mozilla/javascript/LambdaConstructor.java

@@ -127,9 +127,17 @@ protected Constructable getTargetConstructor() {
         return targetConstructor;
     }
 
+    public boolean isCallable() {
+        return (flags & CONSTRUCTOR_FUNCTION) != 0;
+    }
+
+    public boolean isConstructable() {
+        return (flags & CONSTRUCTOR_NEW) != 0;
+    }
+
     @Override
     public Object call(Context cx, Scriptable scope, Scriptable thisObj, Object[] args) {
-        if ((flags & CONSTRUCTOR_FUNCTION) == 0) {
+        if (!isCallable()) {
             throw ScriptRuntime.typeErrorById("msg.constructor.no.function", getFunctionName());
         }
         scope = getDeclarationScope();
@@ -141,7 +149,7 @@ public Object call(Context cx, Scriptable scope, Scriptable thisObj, Object[] ar
 
     @Override
     public Scriptable construct(Context cx, Scriptable scope, Object[] args) {
-        if ((flags & CONSTRUCTOR_NEW) == 0) {
+        if (!isConstructable()) {
             throw ScriptRuntime.typeErrorById("msg.no.new", getFunctionName());
         }
         return fireConstructor(cx, getDeclarationScope(), args);

rhino/src/main/java/org/mozilla/javascript/NativeReflect.java

@@ -14,6 +14,7 @@
  * This class implements the Reflect object.
  *
  * @author Ronald Brill
+ * @author Lai Quang Duong
  */
 final class NativeReflect extends ScriptableObject {
     private static final long serialVersionUID = 2920773905356325445L;
@@ -143,6 +144,15 @@ private static Scriptable construct(
             if (result != null) {
                 result.setPrototype((Scriptable) newTargetPrototype);
 
+                // LambdaConstructor could be non-callable (requires "new") or
+                // non-constructable (no "new"). Check its flag to decide.
+                if (ctorBaseFunction instanceof LambdaConstructor
+                        && ((LambdaConstructor) ctorBaseFunction).isConstructable()) {
+                    Scriptable newScriptable = ctorBaseFunction.construct(cx, scope, callArgs);
+                    newScriptable.setPrototype((Scriptable) newTargetPrototype);
+                    return newScriptable;
+                }
+
                 Object val = ctorBaseFunction.call(cx, scope, result, callArgs);
                 if (val instanceof Scriptable) {
                     return (Scriptable) val;

tests/src/test/java/org/mozilla/javascript/tests/es6/NativeReflectTest.java

@@ -460,4 +460,21 @@ public void setPrototypeOfSame() {
                         + "+ ' ' + Reflect.setPrototypeOf(o3, proto)";
         Utils.assertWithAllModes_ES6("true true true", js);
     }
+
+    @Test
+    public void constructSubclassBuiltin() {
+        String js =
+                "function CustomSet() {\n"
+                        + "  return Reflect.construct(Set, arguments, this.constructor);\n"
+                        + "}\n"
+                        + "CustomSet.prototype = Object.create(Set.prototype);\n"
+                        + "CustomSet.prototype.constructor = CustomSet;\n"
+                        + "var set = new CustomSet([1, 2, 3]);\n"
+                        + "set.add(4);\n"
+                        + "'' + Array.from(set)"
+                        + " + ' ' + (set instanceof CustomSet)"
+                        + " + ' ' + (set instanceof Set)"
+                        + " + ' ' + (Object.getPrototypeOf(set) === CustomSet.prototype)";
+        Utils.assertWithAllModes_ES6("1,2,3,4 true true true", js);
+    }
 }