Add QJSValue::deleteProperty() function

This makes it possible to delete a property without relying on passing
a QJSValue of invalid type to setProperty() (the invalid type is going
to be removed).

Task-number: QTBUG-23604
Change-Id: I653b3349050ad1aac1cf6ccc8547c753abbb9f1d
Reviewed-by: Simon Hausmann <simon.hausmann@nokia.com>
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@nokia.com>

src/declarative/qml/v8/qjsvalue.cpp

@@ -915,7 +915,7 @@ QJSValue QJSValue::property(quint32 arrayIndex) const
   built-in properties, such as the \c{length} property of Array objects
   or meta properties of QObject objects.
 
-  \sa property()
+  \sa property(), deleteProperty()
 */
 void QJSValue::setProperty(const QString& name, const QJSValue& value)
 {
@@ -943,6 +943,33 @@ void QJSValue::setProperty(quint32 arrayIndex, const QJSValue& value)
     d->setProperty(arrayIndex, QJSValuePrivate::get(value));
 }
 
+/*!
+  Attempts to delete this object's property of the given \a name.
+  Returns true if the property was deleted, otherwise returns false.
+
+  The behavior of this function is consistent with the JavaScript
+  delete operator. In particular:
+
+  \list
+  \o Non-configurable properties cannot be deleted.
+  \o This function will return true even if this object doesn't
+     have a property of the given \a name (i.e., non-existent
+     properties are "trivially deletable").
+  \o If this object doesn't have an own property of the given
+     \a name, but an object in the prototype() chain does, the
+     prototype object's property is not deleted, and this function
+     returns true.
+  \endlist
+
+  \sa setProperty(), hasOwnProperty()
+*/
+bool QJSValue::deleteProperty(const QString &name)
+{
+    Q_D(QJSValue);
+    QScriptIsolate api(d->engine());
+    return d->deleteProperty(name);
+}
+
 /*!
   Returns true if this object has a property of the given \a name,
   otherwise returns false.

src/declarative/qml/v8/qjsvalue.h

@@ -134,6 +134,8 @@ class Q_DECLARATIVE_EXPORT QJSValue
     QJSValue property(quint32 arrayIndex) const;
     void setProperty(quint32 arrayIndex, const QJSValue &value);
 
+    bool deleteProperty(const QString &name);
+
     QJSValue::PropertyFlags propertyFlags(const QString &name) const;
 
     QJSValue call(const QJSValue &thisObject = QJSValue(),

tests/auto/declarative/qjsvalue/tst_qjsvalue.cpp

@@ -1843,6 +1843,50 @@ void tst_QJSValue::hasProperty_changePrototype()
     QVERIFY(obj.hasOwnProperty("foo"));
 }
 
+void tst_QJSValue::deleteProperty_basic()
+{
+    QJSEngine eng;
+    QJSValue obj = eng.newObject();
+    // deleteProperty() behavior matches JS delete operator
+    QVERIFY(obj.deleteProperty("foo"));
+
+    obj.setProperty("foo", 123);
+    QVERIFY(obj.deleteProperty("foo"));
+    QVERIFY(!obj.hasOwnProperty("foo"));
+}
+
+void tst_QJSValue::deleteProperty_globalObject()
+{
+    QJSEngine eng;
+    QJSValue global = eng.globalObject();
+    // deleteProperty() behavior matches JS delete operator
+    QVERIFY(global.deleteProperty("foo"));
+
+    global.setProperty("foo", 123);
+    QVERIFY(global.deleteProperty("foo"));
+    QVERIFY(!global.hasProperty("foo"));
+
+    QVERIFY(global.deleteProperty("Math"));
+    QVERIFY(!global.hasProperty("Math"));
+
+    QVERIFY(!global.deleteProperty("NaN")); // read-only
+    QVERIFY(global.hasProperty("NaN"));
+}
+
+void tst_QJSValue::deleteProperty_inPrototype()
+{
+    QJSEngine eng;
+    QJSValue obj = eng.newObject();
+    QJSValue proto = eng.newObject();
+    obj.setPrototype(proto);
+
+    proto.setProperty("foo", 123);
+    QVERIFY(obj.hasProperty("foo"));
+    // deleteProperty() behavior matches JS delete operator
+    QVERIFY(obj.deleteProperty("foo"));
+    QVERIFY(obj.hasProperty("foo"));
+}
+
 void tst_QJSValue::getSetProperty_HooliganTask162051()
 {
     QJSEngine eng;

tests/auto/declarative/qjsvalue/tst_qjsvalue.h

@@ -117,6 +117,10 @@ private slots:
     void hasProperty_globalObject();
     void hasProperty_changePrototype();
 
+    void deleteProperty_basic();
+    void deleteProperty_globalObject();
+    void deleteProperty_inPrototype();
+
     void getSetPrototype_cyclicPrototype();
     void getSetPrototype_evalCyclicPrototype();
     void getSetPrototype_eval();