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
diff --git a/test/mjsunit/harmony/object-observe.js b/test/mjsunit/harmony/object-observe.js
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index 0000000000000000000000000000000000000000..a7a04f62e0558861a4413d2242f524309a52f839
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+++ b/test/mjsunit/harmony/object-observe.js
@@ -0,0 +1,238 @@
+// 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
+
+var allObservers = [];
+function reset() {
+  allObservers.forEach(function(observer) { observer.reset(); });
+}
+
+function createObserver() {
+  var observer = {
+    records: undefined,
+    callbackCount: 0,
+    reset: function() {
+      this.records = undefined;
+      this.callbackCount = 0;
+    },
+    assertNotCalled: function() {
+      assertEquals(undefined, this.records);
+      assertEquals(0, this.callbackCount);
+    },
+    assertCalled: function() {
+      assertEquals(1, this.callbackCount);

[rossberg, 2012/10/25 13:22:32]

Suggestion: make the count an argument.

[rafaelw, 2012/10/25 14:02:19]

I don't think we'll ever want to have been called more than once.

On 2012/10/25 13:22:32, rossberg wrote:

+    },
+    assertRecordCount: function(count) {
+      this.assertCalled();
+      assertEquals(count, this.records.length);
+    },
+    assertCallbackRecords: function(recs) {
+      this.assertRecordCount(recs.length);
+      for (var i = 0; i < recs.length; i++) {
+        assertSame(this.records[i].object, recs[i].object);
+        assertEquals('string', typeof recs[i].type);
+        assertPropertiesEqual(this.records[i], recs[i]);
+      }
+    }
+  };
+
+  observer.callback = function(r) {
+    assertEquals('object', typeof r);
+    assertTrue(r instanceof Array)
+    this.records = r;
+    this.callbackCount++;
+  }.bind(observer);

[rossberg, 2012/10/25 13:22:32]

Perhaps not bind to the observer, but rather assert that this===undefined
inside.

[rafaelw, 2012/10/25 14:02:19]

Done.

+
+  observer.reset();
+  allObservers.push(observer);
+  return observer;
+}
+
+var observer = createObserver();
+assertEquals("function", typeof observer.callback);

[rossberg, 2012/10/25 13:22:32]

Nit: this seems a bit redundant.

[rafaelw, 2012/10/25 14:02:19]

Good catch. That was throw away code I used to track down a typo.

On 2012/10/25 13:22:32, rossberg wrote:

+var obj = {};
+
+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", observer.callback); }, TypeError);
+assertThrows(function() { Object.observe(obj, nonFunction); }, TypeError);
+assertThrows(function() { Object.observe(obj, frozenFunction); }, TypeError);
+
+// Object.unobserve
+assertThrows(function() { Object.unobserve(4, observer.callback); }, TypeError);
+
+// Object.notify
+assertThrows(function() { Object.notify(obj, {}); }, TypeError);
+assertThrows(function() { Object.notify(obj, { type: 4 }); }, TypeError);
+Object.notify(obj, changeRecordWithAccessor);
+assertFalse(recordCreated);
+
+// Object.deliverChangeRecords
+assertThrows(function() { Object.deliverChangeRecords(nonFunction); }, TypeError);
+
+// Multiple records are delivered.
+Object.observe(obj, observer.callback);
+Object.notify(obj, {
+  object: obj,
+  type: 'updated',
+  name: 'foo',
+  expando: 1
+});
+
+Object.notify(obj, {
+  object: obj,
+  type: 'deleted',
+  name: 'bar',
+  expando2: 'str'
+});
+Object.deliverChangeRecords(observer.callback);
+observer.assertCallbackRecords([
+  { object: obj, name: 'foo', type: 'updated', expando: 1 },
+  { object: obj, name: 'bar', type: 'deleted', expando2: 'str' }
+]);
+
+// No delivery takes place if no records are pending
+reset();
+Object.deliverChangeRecords(observer.callback);
+observer.assertNotCalled();
+
+// Multiple observation has no effect.
+reset();
+Object.observe(obj, observer.callback);
+Object.observe(obj, observer.callback);
+Object.notify(obj, {
+  type: 'foo',
+});
+Object.deliverChangeRecords(observer.callback);
+observer.assertCalled();
+
+// Observation can be stopped.
+reset();
+Object.unobserve(obj, observer.callback);
+Object.notify(obj, {
+  type: 'foo',
+});
+Object.deliverChangeRecords(observer.callback);
+observer.assertNotCalled();
+
+// Multiple unobservation has no effect
+reset();
+Object.unobserve(obj, observer.callback);
+Object.unobserve(obj, observer.callback);
+Object.notify(obj, {
+  type: 'foo',
+});
+Object.deliverChangeRecords(observer.callback);
+observer.assertNotCalled();
+
+// Re-observation works and only includes changeRecords after of call.
+reset();
+Object.notify(obj, {
+  type: 'foo',
+});
+Object.observe(obj, observer.callback);
+Object.notify(obj, {
+  type: 'foo',
+});
+records = undefined;
+Object.deliverChangeRecords(observer.callback);
+observer.assertRecordCount(1);
+
+// Observing a continuous stream of changes, while itermittantly unobserving.
+reset();
+Object.observe(obj, observer.callback);
+Object.notify(obj, {
+  type: 'foo',
+  val: 1
+});
+
+Object.unobserve(obj, observer.callback);
+Object.notify(obj, {
+  type: 'foo',
+  val: 2
+});
+
+Object.observe(obj, observer.callback);
+Object.notify(obj, {
+  type: 'foo',
+  val: 3
+});
+
+Object.unobserve(obj, observer.callback);
+Object.notify(obj, {
+  type: 'foo',
+  val: 4
+});
+
+Object.observe(obj, observer.callback);
+Object.notify(obj, {
+  type: 'foo',
+  val: 5
+});
+
+Object.unobserve(obj, observer.callback);
+Object.deliverChangeRecords(observer.callback);
+observer.assertCallbackRecords([
+  { object: obj, type: 'foo', val: 1 },
+  { object: obj, type: 'foo', val: 3 },
+  { object: obj, type: 'foo', val: 5 }
+]);
+
+// Observing multiple objects; records appear in order;.
+reset();
+var obj2 = {};
+var obj3 = {}
+Object.observe(obj, observer.callback);
+Object.observe(obj3, observer.callback);
+Object.observe(obj2, observer.callback);
+Object.notify(obj, {
+  type: 'foo',
+});
+Object.notify(obj2, {
+  type: 'foo',
+});
+Object.notify(obj3, {
+  type: 'foo',
+});
+Object.deliverChangeRecords(observer.callback);
+observer.assertCallbackRecords([
+  { object: obj, type: 'foo' },
+  { object: obj2, type: 'foo' },
+  { object: obj3, type: 'foo' }
+]);