perf(change_detection): use object pools not to create unnecessary garbage

modules/change_detection/src/change_detection_jit_generator.es6

@@ -43,7 +43,7 @@ import {
  *   var address0;
  *   var city1;
  *   var change;
- *   var changes = [];
+ *   var changes = null;
  *   var temp;
  *   var context = this.context;
  * 
@@ -60,14 +60,15 @@ import {
  * 
  *   city1 = address0.city;
  *   if (city1 !== this.city1) {
- *     changes.push(ChangeDetectionUtil.simpleChangeRecord(this.protos[1].bindingMemento, this.city1, city1));
+ *     changes = ChangeDetectionUtil.addRecord(changes,
+ *       ChangeDetectionUtil.simpleChangeRecord(this.protos[1].bindingMemento, this.city1, city1));
  *     this.city1 = city1;
  *   }
  * 
  *   if (changes.length > 0) {
  *     if(throwOnChange) ChangeDetectionUtil.throwOnChange(this.protos[1], changes[0]);
  *     this.dispatcher.onRecordChange('address.city', changes);
- *     changes = [];
+ *     changes = null;
  *   }
  * }
  * 
@@ -144,7 +145,7 @@ ${localDefinitions}
 ${changeDefinitions}
 var ${TEMP_LOCAL};
 var ${CHANGE_LOCAL};
-var ${CHANGES_LOCAL} = [];
+var ${CHANGES_LOCAL} = null;
 
 context = this.context;
 ${records}
@@ -153,10 +154,10 @@ ${records}
 
 function notifyTemplate(index:number):string{
   return  `
-if (${CHANGES_LOCAL}.length > 0) {
+if (${CHANGES_LOCAL} && ${CHANGES_LOCAL}.length > 0) {
   if(throwOnChange) ${UTIL}.throwOnChange(${PROTOS_ACCESSOR}[${index}], ${CHANGES_LOCAL}[0]);
   ${DISPATCHER_ACCESSOR}.onRecordChange(${PROTOS_ACCESSOR}[${index}].groupMemento, ${CHANGES_LOCAL});
-  ${CHANGES_LOCAL} = [];
+  ${CHANGES_LOCAL} = null;
 }
 `;
 }
@@ -166,7 +167,8 @@ function structuralCheckTemplate(selfIndex:number, field:string, context:string,
   return `
 ${CHANGE_LOCAL} = ${UTIL}.structuralCheck(${field}, ${context});
 if (${CHANGE_LOCAL}) {
-  ${CHANGES_LOCAL}.push(${UTIL}.changeRecord(${PROTOS_ACCESSOR}[${selfIndex}].bindingMemento, ${CHANGE_LOCAL}));
+  ${CHANGES_LOCAL} = ${UTIL}.addRecord(${CHANGES_LOCAL},
+    ${UTIL}.changeRecord(${PROTOS_ACCESSOR}[${selfIndex}].bindingMemento, ${CHANGE_LOCAL}));
   ${field} = ${CHANGE_LOCAL}.currentValue;
 }
 ${notify}
@@ -222,7 +224,8 @@ if (${cond}) {
 }
 
 function addSimpleChangeRecordTemplate(protoIndex:number, oldValue:string, newValue:string) {
-  return `${CHANGES_LOCAL}.push(${UTIL}.simpleChangeRecord(${PROTOS_ACCESSOR}[${protoIndex}].bindingMemento, ${oldValue}, ${newValue}));`;
+  return `${CHANGES_LOCAL} = ${UTIL}.addRecord(${CHANGES_LOCAL},
+    ${UTIL}.simpleChangeRecord(${PROTOS_ACCESSOR}[${protoIndex}].bindingMemento, ${oldValue}, ${newValue}));`;
 }
 
 

modules/change_detection/src/change_detection_util.js

@@ -19,6 +19,72 @@ export class SimpleChange {
   }
 }
 
+var _simpleChangesIndex = 0;
+var _simpleChanges = [
+  new SimpleChange(null, null),
+  new SimpleChange(null, null),
+  new SimpleChange(null, null),
+  new SimpleChange(null, null),
+  new SimpleChange(null, null),
+  new SimpleChange(null, null),
+  new SimpleChange(null, null),
+  new SimpleChange(null, null),
+  new SimpleChange(null, null),
+  new SimpleChange(null, null),
+  new SimpleChange(null, null),
+  new SimpleChange(null, null),
+  new SimpleChange(null, null),
+  new SimpleChange(null, null),
+  new SimpleChange(null, null),
+  new SimpleChange(null, null),
+  new SimpleChange(null, null),
+  new SimpleChange(null, null),
+  new SimpleChange(null, null),
+  new SimpleChange(null, null)
+]
+
+var _changeRecordsIndex = 0;
+var _changeRecords = [
+  new ChangeRecord(null, null),
+  new ChangeRecord(null, null),
+  new ChangeRecord(null, null),
+  new ChangeRecord(null, null),
+  new ChangeRecord(null, null),
+  new ChangeRecord(null, null),
+  new ChangeRecord(null, null),
+  new ChangeRecord(null, null),
+  new ChangeRecord(null, null),
+  new ChangeRecord(null, null),
+  new ChangeRecord(null, null),
+  new ChangeRecord(null, null),
+  new ChangeRecord(null, null),
+  new ChangeRecord(null, null),
+  new ChangeRecord(null, null),
+  new ChangeRecord(null, null),
+  new ChangeRecord(null, null),
+  new ChangeRecord(null, null),
+  new ChangeRecord(null, null),
+  new ChangeRecord(null, null)
+]
+
+function _simpleChange(previousValue, currentValue) {
+  var index = _simpleChangesIndex++ % 20;
+  var s = _simpleChanges[index];
+  s.previousValue = previousValue;
+  s.currentValue = currentValue;
+  return s;
+}
+
+function _changeRecord(bindingMemento, change) {
+  var index = _changeRecordsIndex++ % 20;
+  var s = _changeRecords[index];
+  s.bindingMemento = bindingMemento;
+  s.change = change;
+  return s;
+}
+
+var _singleElementList = [null];
+
 export class ChangeDetectionUtil {
   static unitialized() {
     return uninitialized;
@@ -128,11 +194,29 @@ export class ChangeDetectionUtil {
     throw new ExpressionChangedAfterItHasBeenChecked(proto, change);
   }
 
+  static simpleChange(previousValue:any, currentValue:any):SimpleChange {
+    return _simpleChange(previousValue, currentValue);
+  }
+
   static changeRecord(memento:any, change:any):ChangeRecord {
-    return new ChangeRecord(memento, change);
+    return _changeRecord(memento, change);
   }
 
   static simpleChangeRecord(memento:any, previousValue:any, currentValue:any):ChangeRecord {
-    return new ChangeRecord(memento, new SimpleChange(previousValue, currentValue));
+    return _changeRecord(memento, _simpleChange(previousValue, currentValue));
+  }
+
+  static addRecord(updatedRecords:List, changeRecord:ChangeRecord):List {
+    if (isBlank(updatedRecords)) {
+      updatedRecords = _singleElementList;
+      updatedRecords[0] = changeRecord;
+
+    } else if (updatedRecords === _singleElementList) {
+      updatedRecords = [_singleElementList[0], changeRecord];
+
+    } else {
+      ListWrapper.push(updatedRecords, changeRecord);
+    }
+    return updatedRecords;
   }
 }

modules/change_detection/src/dynamic_change_detector.js

@@ -62,7 +62,8 @@ export class DynamicChangeDetector extends AbstractChangeDetector {
 
       if (isPresent(change)) {
         currentGroup = proto.groupMemento;
-        updatedRecords = this._addRecord(updatedRecords, proto, change);
+        var record = ChangeDetectionUtil.changeRecord(proto.bindingMemento, change);
+        updatedRecords = ChangeDetectionUtil.addRecord(updatedRecords, record);
       }
 
       if (proto.lastInGroup && isPresent(updatedRecords)) {
@@ -100,7 +101,7 @@ export class DynamicChangeDetector extends AbstractChangeDetector {
       this._setChanged(proto, true);
 
       if (proto.lastInBinding) {
-        return new SimpleChange(prevValue, currValue);
+        return ChangeDetectionUtil.simpleChange(prevValue, currValue);
       } else {
         return null;
       }
@@ -164,22 +165,6 @@ export class DynamicChangeDetector extends AbstractChangeDetector {
     return change;
   }
 
-  _addRecord(updatedRecords:List, proto:ProtoRecord, change):List {
-    // we can use a pool of change records not to create extra garbage
-    var record = ChangeDetectionUtil.changeRecord(proto.bindingMemento, change);
-    if (isBlank(updatedRecords)) {
-      updatedRecords = _singleElementList;
-      updatedRecords[0] = record;
-
-    } else if (updatedRecords === _singleElementList) {
-      updatedRecords = [_singleElementList[0], record];
-
-    } else {
-      ListWrapper.push(updatedRecords, record);
-    }
-    return updatedRecords;
-  }
-
   _readContext(proto:ProtoRecord) {
     return this.values[proto.contextIndex];
   }

modules/change_detection/test/change_detection_spec.js

@@ -59,6 +59,10 @@ export function main() {
             expect(dispatcher.log).toEqual(['name=misko']);
             dispatcher.clear();
 
+            cd.detectChanges();
+            expect(dispatcher.log).toEqual([]);
+            dispatcher.clear();
+
             person.name = "Misko";
             cd.detectChanges();
             expect(dispatcher.log).toEqual(['name=Misko']);