[es6] Implement for-of iterator finalization

test/mjsunit/harmony/iterator-close.js

+// Copyright 2016 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.
+
+
+function* g() { yield 42; return 88 };
+
+
+// Return method is "undefined".
+{
+  g.prototype.return = null;
+
+  assertEquals(undefined, (() => {
+    for (let x of g()) { break; }
+  })());
+
+  assertEquals(undefined, (() => {
+    for (x of g()) { break; }
+  })());
+
+  assertThrowsEquals(() => {
+    for (let x of g()) { throw 42; }
+  }, 42);
+
+  assertThrowsEquals(() => {
+    for (x of g()) { throw 42; }
+  }, 42);
+
+  assertEquals(42, (() => {
+    for (let x of g()) { return 42; }
+  })());
+
+  assertEquals(42, (() => {
+    for (x of g()) { return 42; }
+  })());
+
+  assertEquals(42, eval('for (let x of g()) { x; }'));
+
+  assertEquals(42, eval('for (let x of g()) { x; }'));
+}
+
+
+// Return method is not callable.
+{
+  g.prototype.return = 666;
+
+  assertThrows(() => {
+    for (let x of g()) { break; }
+  }, TypeError);
+
+  assertThrows(() => {
+    for (x of g()) { break; }
+  }, TypeError);
+
+  assertThrows(() => {
+    for (let x of g()) { throw 666; }
+  }, TypeError);
+
+  assertThrows(() => {
+    for (x of g()) { throw 666; }
+  }, TypeError);
+
+  assertThrows(() => {
+    for (let x of g()) { return 666; }
+  }, TypeError);
+
+  assertThrows(() => {
+    for (x of g()) { return 666; }
+  }, TypeError);
+
+  assertEquals(42, eval('for (let x of g()) { x; }'));
+
+  assertEquals(42, eval('for (let x of g()) { x; }'));
+}
+
+
+// Return method does not return an object.
+{
+  g.prototype.return = () => 666;
+
+  assertThrows(() => {
+    for (let x of g()) { break; }
+  }, TypeError);
+
+  assertThrows(() => {
+    for (x of g()) { break; }
+  }, TypeError);
+
+  assertThrows(() => {
+    for (let x of g()) { throw 666; }
+  }, TypeError);
+
+  assertThrows(() => {
+    for (x of g()) { throw 666; }
+  }, TypeError);
+
+  assertThrows(() => {
+    for (let x of g()) { return 666; }
+  }, TypeError);
+
+  assertThrows(() => {
+    for (x of g()) { return 666; }
+  }, TypeError);
+
+  assertEquals(42, eval('for (let x of g()) { x; }'));
+
+  assertEquals(42, eval('for (x of g()) { x; }'));
+}
+
+
+// Return method returns an object.
+{
+  let log = [];
+  g.prototype.return = (...args) => { log.push(args); return {} };
+
+  log.length = 0;
+  for (let x of g()) { break; }
+  assertEquals([[]], log);
+
+  log.length = 0;
+  for (x of g()) { break; }
+  assertEquals([[]], log);
+
+  log.length = 0;
+  assertThrowsEquals(() => {
+    for (let x of g()) { throw 42; }
+  }, 42);
+  assertEquals([[]], log);
+
+  log.length = 0;
+  assertThrowsEquals(() => {
+    for (x of g()) { throw 42; }
+  }, 42);
+  assertEquals([[]], log);
+
+  log.length = 0;
+  assertEquals(42, (() => {
+    for (let x of g()) { return 42; }
+  })());
+  assertEquals([[]], log);
+
+  log.length = 0;
+  assertEquals(42, (() => {
+    for (x of g()) { return 42; }
+  })());
+  assertEquals([[]], log);
+
+  log.length = 0;
+  assertEquals(42, eval('for (let x of g()) { x; }'));
+  assertEquals([], log);
+
+  log.length = 0;
+  assertEquals(42, eval('for (x of g()) { x; }'));
+  assertEquals([], log);
+}
+
+
+// Return method throws.
+{
+  let log = [];
+  g.prototype.return = (...args) => { log.push(args); throw 23 };
+
+  log.length = 0;
+  assertThrowsEquals(() => {
+    for (let x of g()) { break; }
+  }, 23);
+  assertEquals([[]], log);
+
+  log.length = 0;
+  assertThrowsEquals(() => {
+    for (x of g()) { break; }
+  }, 23);
+  assertEquals([[]], log);
+
+  log.length = 0;
+  assertThrowsEquals(() => {
+    for (let x of g()) { throw 42; }
+  }, 42);
+  assertEquals([[]], log);
+
+  log.length = 0;
+  assertThrowsEquals(() => {
+    for (x of g()) { throw 42; }
+  }, 42);
+  assertEquals([[]], log);
+
+  log.length = 0;
+  assertThrowsEquals(() => {
+    for (let x of g()) { return 42; }
+  }, 23);
+  assertEquals([[]], log);
+
+  log.length = 0;
+  assertThrowsEquals(() => {
+    for (x of g()) { return 42; }
+  }, 23);
+  assertEquals([[]], log);
+
+  log.length = 0;
+  assertEquals(42, eval('for (let x of g()) { x; }'));
+  assertEquals([], log);
+
+  log.length = 0;
+  assertEquals(42, eval('for (x of g()) { x; }'));
+  assertEquals([], log);
+}
+
+
+// Next method throws.
+{
+  let log = [];
+  g.prototype.next = (...args) => { log.push(1, args); throw 666; };
+  g.prototype.return = (...args) => { log.push(2, args); return {} };
+
+  log.length = 0;
+  assertThrowsEquals(() => {
+    for (let x of g()) {}
+  }, 666);
+  assertEquals([1, [], 2, []], log);
+
+  log.length = 0;
+  assertThrowsEquals(() => {
+    for (x of g()) {}
+  }, 666);
+  assertEquals([1, [], 2, []], log);
+}

[Dan Ehrenberg, 2016/02/16 21:18:30]

Can you write some tests to ensure that at least some of these cases work when
you have nested for loops, to ensure that scoping for various variables (the
anonymous var_completion, .catch, etc) works out in a properly nested way? In
particular, testing that IteratorClose gets called for the inner or outer one as
appropriate, and the right exception gets propagated.

[rossberg, 2016/02/17 12:54:45]

Done.