Add ES5 Object.isExtensible and Object.preventExtensions.

test/mjsunit/object-prevent-extensions.js

+// Copyright 2010 the V8 project authors. All rights reserved.
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+// modification, are permitted provided that the following conditions are
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+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Tests the Object.preventExtensions method - ES 15.2.3.10
+
+
+var obj1 = {};
+// Extensible defaults to true.
+assertTrue(Object.isExtensible(obj1));
+Object.preventExtensions(obj1);
+
+// Make sure the is_extensible flag is set. 
+assertFalse(Object.isExtensible(obj1));
+// Try adding a new property.
+try {
+  obj1.x = 42;
+  assertUnreachable();
+} catch (e) {
+  assertTrue(/object is not extensible/.test(e));
+}
+assertEquals(undefined, obj1.x);
+
+// Try adding a new element.
+try {
+  obj1[1] = 42;
+  assertUnreachable();
+} catch (e) {
+  assertTrue(/object is not extensible/.test(e));
+}
+assertEquals(undefined, obj1[1]);
+
+
+// Try when the object has an existing property.
+var obj2 = {};
+assertTrue(Object.isExtensible(obj2));
+obj2.x = 42;
+assertEquals(42, obj2.x);
+assertTrue(Object.isExtensible(obj2));
+
+Object.preventExtensions(obj2);
+assertEquals(42, obj2.x);
+
+try {
+  obj2.y = 42;
+  assertUnreachable();
+} catch (e) {
+  assertTrue(/object is not extensible/.test(e));
+}
+
+// obj2.y should still be undefined.
+assertEquals(undefined, obj2.y);
+// Make sure we can still write values to obj.x.
+obj2.x = 43;
+assertEquals(43, obj2.x)
+
+try {
+  obj2.y = new function() { return 42; };
+  assertUnreachable();
+} catch (e) {
+  assertTrue(/object is not extensible/.test(e));
+}
+// obj2.y should still be undefined.
+assertEquals(undefined, obj2.y);
+assertEquals(43, obj2.x)
+
+try {
+  Object.defineProperty(obj2, "y", {value: 42});
+} catch (e) {
+  assertTrue(/object is not extensible/.test(e));
+}
+
+// obj2.y should still be undefined.
+assertEquals(undefined, obj2.y);
+assertEquals(43, obj2.x);
+
+try {
+  obj2[1] = 42;
+} catch (e) {
+  assertTrue(/object is not extensible/.test(e));
+}
+
+assertEquals(undefined, obj2[1]);
+
+var arr = new Array();
+arr[1] = 10;
+
+Object.preventExtensions(arr);
+
+try {
+  arr[2] = 42;
+  assertUnreachable();
+} catch (e) {
+  assertTrue(/object is not extensible/.test(e));
+}
+assertEquals(10, arr[1]);
+
+// We should still be able to change exiting elements.
+arr[1]= 42;
+assertEquals(42, arr[1]);
+
+
+// Test the the extensible flag is not inherited.
+var parent = {};
+parent.x = 42;
+Object.preventExtensions(parent);
+
+var child = Object.create(parent);
+
+// We should be able to add new properties to the child object.
+child.y = 42;
+
+// This should have no influence on the parent class.
+try {
+  parent.y = 29;
+  assertUnreachable();
+} catch (e) {
+  assertTrue(/object is not extensible/.test(e));
+}
+
+
+// Test that attributes on functions are also handled correctly.
+function foo() {
+  return 42;
+}
+
+Object.preventExtensions(foo);
+
+try {
+  foo.x = 29;
+  assertUnreachable();
+} catch (e) {
+  assertTrue(/object is not extensible/.test(e));
+}