v8/test/mjsunit/es6/proxies-get.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.

// Flags: --allow-natives-syntax

(function testBasicFunctionality() {
   var target = {
     target_one: 1,
     property: "value"
   };

   var handler = {handler:1};

   var proxy = new Proxy(target, handler);
   assertEquals("value", proxy.property);
   assertEquals(undefined, proxy.nothing);
   assertEquals(undefined, proxy.handler);

   handler.get = function() { return "value 2" };
   assertEquals("value 2", proxy.property);
   assertEquals("value 2", proxy.nothing);
   assertEquals("value 2", proxy.handler);

   var handler2 = new Proxy({get: function() { return "value 3" }},{});
   var proxy2 = new Proxy(target, handler2);
   assertEquals("value 3", proxy2.property);
   assertEquals("value 3", proxy2.nothing);
   assertEquals("value 3", proxy2.handler);
})();

(function testThrowOnGettingTrap() {
  var handler = new Proxy({}, {get: function(){ throw Error() }});
  var proxy = new Proxy({}, handler);
  assertThrows("proxy.property", Error);
})();

(function testThrowOnTrapNotCallable() {
  var handler = new Proxy({}, {get: 'not_callable' });
  var proxy = new Proxy({}, handler);
  assertThrows("proxy.property", Error);
})();

(function testFallback() {
  var target = {property:"value"};
  var proxy = new Proxy(target, {});
  assertEquals("value", proxy.property);
  assertEquals(undefined, proxy.property2);
})();

(function testFallbackUndefinedTrap() {
  var handler = new Proxy({}, {get: function(){ return undefined }});
  var target = {property:"value"};
  var proxy = new Proxy(target, handler);
  assertEquals("value", proxy.property);
  assertEquals(undefined, proxy.property2);
})();

(function testFailingInvariant() {
  var target = {};
  var handler = { get: function(r, p){ if (p != "key4") return "value" }}
  var proxy = new Proxy(target, handler);
  assertEquals("value", proxy.property);
  assertEquals("value", proxy.key);
  assertEquals("value", proxy.key2);
  assertEquals("value", proxy.key3);

  // Define a non-configurable, non-writeable property on the target for
  // which the handler will return a different value.
  Object.defineProperty(target, "key", {
    configurable: false,
    writable: false,
    value: "different value"
  });
  assertEquals("value", proxy.property);
  assertThrows(function(){ proxy.key }, TypeError);
  assertEquals("value", proxy.key2);
  assertEquals("value", proxy.key3);

  // Define a non-configurable getter on the target for which the handler
  // will return a value, according to the spec we do not throw.
  Object.defineProperty(target, "key2", {
    configurable: false,
    get: function() { return "different value" }
  });
  assertEquals("value", proxy.property);
  assertThrows(function(){ proxy.key }, TypeError);
  assertEquals("value", proxy.key2);
  assertEquals("value", proxy.key3);

  // Define a non-configurable setter without a corresponding getter on the
  // target for which the handler will return a value.
  Object.defineProperty(target, "key3", {
    configurable: false,
    set: function() { }
  });
  assertEquals("value", proxy.property);
  assertThrows(function(){ proxy.key }, TypeError);
  assertEquals("value", proxy.key2);
  assertThrows(function(){ proxy.key3 }, TypeError);

  // Define a non-configurable setter without a corresponding getter on the
  // target for which the handler will return undefined.
  Object.defineProperty(target, "key4", {
    configurable: false,
    set: function() { }
  });
  assertSame(undefined, proxy.key4);
})();

(function testGetInternalIterators() {
  var log = [];
  var array = [1,2,3,4,5]
  var origIt = array[Symbol.iterator]();
  var it = new Proxy(origIt, {
    get(t, name) {
      log.push(`[[Get]](iterator, ${String(name)})`);
      return Reflect.get(t, name);
    },
    set(t, name, val) {
      log.push(`[[Set]](iterator, ${String(name)}, ${String(val)})`);
      return Reflect.set(t, name, val);
    }
  });

  assertThrows(function() {
    for (var v of it) log.push(v);
  }, TypeError);
  assertEquals([
    "[[Get]](iterator, Symbol(Symbol.iterator))",
    "[[Get]](iterator, next)"
  ], log);
})();

(function testGetterWithSideEffect() {
  var obj = {
    key: 0
  }
  assertEquals(obj.key, 0);
  var p = new Proxy(obj, {});
  var q = new Proxy(p, {
    get(target, name) {
      if (name != 'key') return Reflect.get(target, name);
      target.key++;
      return target.key;
    }
  });

  assertEquals(0, p.key);
  // Assert the trap is not called twice.
  assertEquals(1, q.key);
})();

(function testReceiverWithTrap() {
  var obj = {};
  var p = new Proxy(obj, {
    get(target, name, receiver) {
      if (name != 'key') return Reflect.get(target, name);

      assertSame(target, obj);
      assertSame(receiver, p);
      return 42;
    }
  });
  assertEquals(42, p.key);
})();

(function testReceiverWithoutTrap() {
  var obj = {
    get prop() {
      assertSame(this, p);
      return 42;
    }
  };
  var p = new Proxy(obj, {});
  assertEquals(42, p.prop);
})();

(function testGetPropertyDetailsBailout() {
  var obj = {
  }
  var p = new Proxy(obj, {
    getOwnPropertyDescriptor() {
      throw new Error('Error from proxy getOwnPropertyDescriptor trap');
    }
  });
  var q = new Proxy(p, {
    get(target, name) {
      return 42;
    }
  });
  assertThrows(function(){ q.prop }, Error,
    'Error from proxy getOwnPropertyDescriptor trap');
})();


(function testGetPropertyDetailsBailout2() {
  var obj = {};
  Object.defineProperty(obj, 'prop', {
    value: 53,
    configurable: false
  });
  var p = new Proxy(obj, {});
  var q = new Proxy(p, {
    get(target, name) {
      return 42;
    }
  });
  assertThrows(function(){ q.prop }, TypeError,
    "'get' on proxy: property 'prop' is a read-only and non-configurable data" +
    " property on the proxy target but the proxy did not return its actual" +
    " value (expected '53' but got '42')");
})();