Initial JS stub implementation of Object.observe. Adds support for .object/.unobserve/.notify/.deli…

test/mjsunit/harmony/object-observe.js

Index: test/mjsunit/harmony/object-observe.js
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+// Copyright 2012 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// 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.
+
+// Flags: --harmony-object-observe
+
+(function() {

[rossberg, 2012/10/24 09:57:24]

Nit: We don't usually turn test cases into iffies, since they are all executed
in a fresh environment anyway.

[rafaelw, 2012/10/24 11:18:04]

Done.

+  var obj = {};
+  var records;
+  var callbackCount = 0;
+  function obs(r) {
+    callbackCount++;
+    records = r;
+  }
+
+  function frozenFunction() {}
+  Object.freeze(frozenFunction);
+  var nonFunction = {};
+  var changeRecordWithAccessor = { type: 'foo' };
+  var recordCreated = false;
+  Object.defineProperty(changeRecordWithAccessor, 'name', {
+    get: function() {
+      recordCreated = true;
+    },
+    enumerable: true
+  })
+
+  // Object.observe
+  assertThrows(function() { Object.observe("non-object", obs); }, TypeError);
+  assertThrows(function() { Object.observe(obj, nonFunction); }, TypeError);
+  assertThrows(function() { Object.observe(obj, frozenFunction); }, TypeError);
+
+  // Object.unobserve
+  assertThrows(function() { Object.unobserve(4, obs); }, TypeError);
+
+  // Object.notify
+  assertThrows(function() { Object.notify(obs, {}); }, TypeError);
+  assertThrows(function() { Object.notify(obs, { type: 4 }); }, TypeError);
+  Object.notify(obs, changeRecordWithAccessor);
+  assertFalse(recordCreated);
+
+  // Object.deliverChangeRecords
+  assertThrows(function() { Object.deliverChangeRecords(nonFunction); }, TypeError);
+
+  // Multiple records are delivered.
+  Object.observe(obj, obs);
+  Object.notify(obj, {
+    object: obj,
+    type: 'updated',
+    name: 'foo',
+    expando: 1
+  });
+
+  Object.notify(obj, {
+    object: obj,
+    type: 'deleted',
+    name: 'bar',
+    expando2: 'str'
+  });
+  Object.deliverChangeRecords(obs);
+  assertEquals(1, callbackCount);
+  assertEquals(2, records.length);
+  assertEquals(obj, records[0].object);
+  assertEquals('foo', records[0].name);
+  assertEquals('updated', records[0].type);
+  assertEquals(1, records[0].expando);
+  assertEquals(obj, records[1].object);
+  assertEquals('bar', records[1].name);
+  assertEquals('deleted', records[1].type);
+  assertEquals('str', records[1].expando2);
+  assertEquals(undefined, records[1].expando);
+
+  // No delivery takes place if no records are pending
+  records = undefined;
+  Object.deliverChangeRecords(obs);
+  assertEquals(1, callbackCount);

[rossberg, 2012/10/24 09:57:24]

Better reset callback count and test for 0. Otherwise it gets messy when you
refactor tests (similarly below).

[rafaelw, 2012/10/24 11:18:04]

Done.

+  assertEquals(undefined, records);
+
+  // Multiple observation has no effect.
+  Object.observe(obj, obs);
+  Object.observe(obj, obs);
+  Object.notify(obj, {
+    type: 'foo',
+  });
+  Object.deliverChangeRecords(obs);
+  assertEquals(2, callbackCount);
+
+  // Observation can be stopped.
+  Object.unobserve(obj, obs);
+  Object.notify(obj, {
+    type: 'foo',
+  });
+  Object.deliverChangeRecords(obs);
+  assertEquals(2, callbackCount);
+
+  // Multiple unobservation has no effect
+  Object.unobserve(obj, obs);
+  Object.unobserve(obj, obs);
+  Object.notify(obj, {
+    type: 'foo',
+  });
+  Object.deliverChangeRecords(obs);
+  assertEquals(2, callbackCount);
+
+  // Re-observation works and only includes changeRecords after of call.
+  Object.notify(obj, {
+    type: 'foo',
+  });
+  Object.observe(obj, obs);
+  Object.notify(obj, {
+    type: 'foo',
+  });
+  records = undefined;
+  Object.deliverChangeRecords(obs);
+  assertEquals(3, callbackCount);
+  assertEquals(1, records.length);
+})()

[rossberg, 2012/10/24 09:57:24]

Other scenarios to test:

- One function observing multiple objects, and check that change records arrive
in order.

- An object being modified, unobserved, modified, reobserved, modified, all
before delivering change records, and check that intermediate changes don't
appear.

[rossberg, 2012/10/24 10:06:52]

- Objects observed by multiple observers (perhaps more interesting once you have
implemented priorities).

[rafaelw, 2012/10/24 11:18:04]

Done.

[rafaelw, 2012/10/24 11:18:04]

Yeah. I think I'd like to add that in the next patch which will implement
prioritized delivery. Cool?

On 2012/10/24 10:06:52, rossberg wrote:

[rossberg, 2012/10/24 12:03:13]

Sounds good.