JSTests/test262/test/language/expressions/yield/star-rhs-iter-nrml-res-done-no-value.js

// Copyright (C) 2016 the V8 project authors. All rights reserved.
// This code is governed by the BSD license found in the LICENSE file.
/*---
esid: sec-generator-function-definitions-runtime-semantics-evaluation
es6id: 14.4.14
description: >
  `value` property is not accessed when iteration is incomplete
info: |
  YieldExpression : yield * AssignmentExpression

  1. Let exprRef be the result of evaluating AssignmentExpression.
  2. Let value be ? GetValue(exprRef).
  3. Let iterator be ? GetIterator(value).
  4. Let received be NormalCompletion(undefined).
  5. Repeat
     a. If received.[[Type]] is normal, then
        i. Let innerResult be ? IteratorNext(iterator, received.[[Value]]).
        ii. Let done be ? IteratorComplete(innerResult).
        iii. If done is true, then
             1. Return ? IteratorValue(innerResult).
features: [generators, Symbol.iterator]
---*/

var badIter = {};
var callCount = 0;
var spyValue = Object.defineProperty({ done: false }, 'value', {
  get: function() {
    callCount += 1;
  }
});
badIter[Symbol.iterator] = function() {
  return {
    next: function() {
      return spyValue;
    }
  };
};
var delegationComplete = false;
function* g() {
  yield * badIter;
  delegationComplete = true;
}
var iter = g();

iter.next();
assert.sameValue(callCount, 0, 'access count (first iteration)');
assert.sameValue(
  delegationComplete, false, 'delegation ongoing (first iteration)'
);

iter.next();
assert.sameValue(callCount, 0, 'access count (second iteration)');
assert.sameValue(
  delegationComplete, false, 'delegation ongoing (second iteration)'
);

spyValue.done = true;
iter.next();
assert.sameValue(callCount, 1, 'access count (final iteration)');
assert.sameValue(delegationComplete, true, 'delegation complete');