v8/test/mjsunit/es6/proxies-has.js

// Copyright 2015 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

var target = {
  "target_one": 1
};
target[0] = 42;
target.__proto__ = {
  "target_two": 2
};
var handler = {
  has: function(target, name) {
    return name == "present" || name == '0';
  }
}

var proxy = new Proxy(target, handler);

// Test simple cases.
assertTrue("present" in proxy);
assertFalse("nonpresent" in proxy);

// Test element cases.
assertTrue(0 in proxy);
assertFalse(1 in proxy);
assertTrue('0' in proxy);
assertFalse('1' in proxy);

var symbol0 = {
  [Symbol.toPrimitive](hint) {
    return 0;
  }
};
var symbol1 = {
  [Symbol.toPrimitive](hint) {
    return 1;
  }
};
assertTrue(symbol0 in proxy);
assertFalse(symbol1 in proxy);

// Test interesting algorithm steps:

// Step 7: Fall through to target if trap is undefined.
handler.has = undefined;
assertTrue("target_one" in proxy);
assertTrue("target_two" in proxy);
assertFalse("in_your_dreams" in proxy);

// Step 8: Result is converted to boolean.
var result = 1;
handler.has = function(t, n) { return result; }
assertTrue("foo" in proxy);
result = {};
assertTrue("foo" in proxy);
result = undefined;
assertFalse("foo" in proxy);
result = "string";
assertTrue("foo" in proxy);

// Step 9b i. Trap result must confirm presence of non-configurable properties
// of the target.
Object.defineProperty(target, "nonconf", {value: 1, configurable: false});
result = false;
assertThrows("'nonconf' in proxy", TypeError);

// Step 9b iii. Trap result must confirm presence of all own properties of
// non-extensible targets.
Object.preventExtensions(target);
assertThrows("'nonconf' in proxy", TypeError);
assertThrows("'target_one' in proxy", TypeError);
assertFalse("target_two" in proxy);
assertFalse("in_your_dreams" in proxy);

// Regression test for crbug.com/570120 (stray JSObject::cast).
(function TestHasPropertyFastPath() {
  var proxy = new Proxy({}, {});
  var object = Object.create(proxy);
  object.hasOwnProperty(0);
})();

(function FalseTargetPropExists() {
  var target2 = {
    attr: 1
  };
  var p = new Proxy(target2, {
    has: function(t, prop) {
      return false;
    }
  });

  assertFalse("attr" in p);
})();

(function TargetHasAccessorProperty() {
  var target = {};
  Object.defineProperty(target, 'prop', {
    get: function() {
      assertSame(this, target);
      return 42;
    },
    configurable: true
  })
  var proxy = new Proxy(target, {
    has: function(t, prop) {
      return false;
    },
  });
  assertFalse('prop' in proxy);
})();

(function TargetHasNonConfigurableProperty() {
  var target = {};
  Object.defineProperty(target, 'prop', {
    value: 42,
    configurable: false,
    writable: true
  })
  var proxy = new Proxy(target, {
    has: function(t, prop) {
      return false;
    },
  });
  assertThrows(function() { 'prop' in proxy; }, TypeError);
})();