perf($parse): execute watched expressions only when the inputs change

With this change, expressions like "firstName + ' ' + lastName | uppercase"
will be analyzed and only the inputs for the expression will be watched
(in this case "firstName" and "lastName"). Only when at least one of the inputs
change, the expression will be evaluated.
This change speeds up simple expressions like `firstName | noop` by ~15%
and more complex expressions like `startDate | date` by ~2500%.
BREAKING CHANGE: all filters are assumed to be stateless functions
Previously it was a good practice to make all filters stateless, but now
it's a requirement in order for the model change-observation to pick up
all changes.
If an existing filter is statefull, it can be flagged as such but keep in
mind that this will result in a significant performance-penalty (or rather
lost opportunity to benefit from a major perf improvement) that will
affect the $digest duration.
To flag a filter as stateful do the following:
myApp.filter('myFilter', function() {
function myFilter(input) { ... };
myFilter.$stateful = true;
return myFilter;
});
Closes#9006Closes#9082

Author: jbedard

benchmarks/parsed-expressions-bp/main.html

@@ -31,6 +31,11 @@
 <labelfor="operators">Binary/Unary operators</label>
 </li>
 
+<li>
+<inputtype="radio" ng-model="expressionType" value="shortCircuitingOperators" id="shortCircuitingOperators">
+<labelfor="shortCircuitingOperators">AND/OR short-circuiting operators</label>
+</li>
+
 <li>
 <inputtype="radio" ng-model="expressionType" value="filters" id="filters">
 <labelfor="filters">Filters</label>
@@ -134,6 +139,17 @@
 <spanbm-pe-watch="-rowIdx * 2 * rowIdx + rowIdx / rowIdx + 1"></span>
 </li>
 
+<ling-switch-when="shortCircuitingOperators" ng-repeat="(rowIdx, row) in ::data">
+<spanbm-pe-watch="rowIdx && row.odd"></span>
+<spanbm-pe-watch="row.odd && row.even"></span>
+<spanbm-pe-watch="row.odd && !row.even"></span>
+<spanbm-pe-watch="row.odd || row.even"></span>
+<spanbm-pe-watch="row.odd || row.even || row.index"></span>
+<spanbm-pe-watch="row.index === 1 || row.index === 2"></span>
+<spanbm-pe-watch="row.num0 < row.num1 && row.num1 < row.num2"></span>
+<spanbm-pe-watch="row.num0 < row.num1 || row.num1 < row.num2"></span>
+</li>
+
 <ling-switch-when="filters" ng-repeat="(rowIdx, row) in ::data">
 <spanbm-pe-watch="rowIdx | noop"></span>
 <spanbm-pe-watch="rowIdx | noop"></span>

src/ng/compile.js

@@ -1725,7 +1725,7 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
 attrs[attrName],newIsolateScopeDirective.name);
 };
 lastValue=isolateBindingContext[scopeName]=parentGet(scope);
-varunwatch=scope.$watch($parse(attrs[attrName],functionparentValueWatch(parentValue){
+varparentValueWatch=functionparentValueWatch(parentValue){
 if(!compare(parentValue,isolateBindingContext[scopeName])){
 // we are out of sync and need to copy
 if(!compare(parentValue,lastValue)){
@@ -1737,7 +1737,9 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
 }
 }
 returnlastValue=parentValue;
-}),null,parentGet.literal);
+};
+parentValueWatch.$stateful=true;
+varunwatch=scope.$watch($parse(attrs[attrName],parentValueWatch),null,parentGet.literal);
 isolateScope.$on('$destroy',unwatch);
 break;
 

src/ng/parse.js

@@ -376,6 +376,10 @@ Lexer.prototype = {
 };
 
 
+functionisConstant(exp){
+returnexp.constant;
+}
+
 /**
  * @constructor
  */
@@ -493,7 +497,8 @@ Parser.prototype = {
 returnextend(function(self,locals){
 returnfn(self,locals,right);
 },{
-constant:right.constant
+constant:right.constant,
+inputs: [right]
 });
 },
 
@@ -505,11 +510,12 @@ Parser.prototype = {
 });
 },
 
-binaryFn: function(left,fn,right){
+binaryFn: function(left,fn,right,isBranching){
 returnextend(function(self,locals){
 returnfn(self,locals,left,right);
 },{
-constant:left.constant&&right.constant
+constant: left.constant&&right.constant,
+inputs: !isBranching&&[left,right]
 });
 },
 
@@ -557,7 +563,9 @@ Parser.prototype = {
 }
 }
 
-returnfunction$parseFilter(self,locals){
+varinputs=[inputFn].concat(argsFn||[]);
+
+returnextend(function$parseFilter(self,locals){
 varinput=inputFn(self,locals);
 if(args){
 args[0]=input;
@@ -571,7 +579,10 @@ Parser.prototype = {
 }
 
 returnfn(input);
-};
+},{
+constant: !fn.$stateful&&inputs.every(isConstant),
+inputs: !fn.$stateful&&inputs
+});
 },
 
 expression: function(){
@@ -588,9 +599,11 @@ Parser.prototype = {
 this.text.substring(0,token.index)+'] can not be assigned to',token);
 }
 right=this.ternary();
-returnfunction$parseAssignment(scope,locals){
+returnextend(function$parseAssignment(scope,locals){
 returnleft.assign(scope,right(scope,locals),locals);
-};
+},{
+inputs: [left,right]
+});
 }
 returnleft;
 },
@@ -615,7 +628,7 @@ Parser.prototype = {
 varleft=this.logicalAND();
 vartoken;
 while((token=this.expect('||'))){
-left=this.binaryFn(left,token.fn,this.logicalAND());
+left=this.binaryFn(left,token.fn,this.logicalAND(),true);
 }
 returnleft;
 },
@@ -624,7 +637,7 @@ Parser.prototype = {
 varleft=this.equality();
 vartoken;
 if((token=this.expect('&&'))){
-left=this.binaryFn(left,token.fn,this.logicalAND());
+left=this.binaryFn(left,token.fn,this.logicalAND(),true);
 }
 returnleft;
 },
@@ -759,7 +772,6 @@ Parser.prototype = {
 // This is used with json array declaration
 arrayDeclaration: function(){
 varelementFns=[];
-varallConstant=true;
 if(this.peekToken().text!==']'){
 do{
 if(this.peek(']')){
@@ -768,9 +780,6 @@ Parser.prototype = {
 }
 varelementFn=this.expression();
 elementFns.push(elementFn);
-if(!elementFn.constant){
-allConstant=false;
-}
 }while(this.expect(','));
 }
 this.consume(']');
@@ -783,13 +792,13 @@ Parser.prototype = {
 returnarray;
 },{
 literal: true,
-constant: allConstant
+constant: elementFns.every(isConstant),
+inputs: elementFns
 });
 },
 
 object: function(){
 varkeys=[],valueFns=[];
-varallConstant=true;
 if(this.peekToken().text!=='}'){
 do{
 if(this.peek('}')){
@@ -801,9 +810,6 @@ Parser.prototype = {
 this.consume(':');
 varvalue=this.expression();
 valueFns.push(value);
-if(!value.constant){
-allConstant=false;
-}
 }while(this.expect(','));
 }
 this.consume('}');
@@ -816,7 +822,8 @@ Parser.prototype = {
 returnobject;
 },{
 literal: true,
-constant: allConstant
+constant: valueFns.every(isConstant),
+inputs: valueFns
 });
 }
 };
@@ -1043,6 +1050,8 @@ function $ParseProvider() {
 parsedExpression=wrapSharedExpression(parsedExpression);
 parsedExpression.$$watchDelegate=parsedExpression.literal ?
 oneTimeLiteralWatchDelegate : oneTimeWatchDelegate;
+}elseif(parsedExpression.inputs){
+parsedExpression.$$watchDelegate=inputsWatchDelegate;
 }
 
 cache[cacheKey]=parsedExpression;
@@ -1057,6 +1066,88 @@ function $ParseProvider() {
 }
 };
 
+functioncollectExpressionInputs(inputs,list){
+for(vari=0,ii=inputs.length;i<ii;i++){
+varinput=inputs[i];
+if(!input.constant){
+if(input.inputs){
+collectExpressionInputs(input.inputs,list);
+}elseif(list.indexOf(input)===-1){// TODO(perf) can we do better?
+list.push(input);
+}
+}
+}
+
+returnlist;
+}
+
+functionexpressionInputDirtyCheck(newValue,oldValueOfValue){
+
+if(newValue==null||oldValueOfValue==null){// null/undefined
+returnnewValue===oldValueOfValue;
+}
+
+if(typeofnewValue==='object'){
+
+// attempt to convert the value to a primitive type
+// TODO(docs): add a note to docs that by implementing valueOf even objects and arrays can
+// be cheaply dirty-checked
+newValue=newValue.valueOf();
+
+if(typeofnewValue==='object'){
+// objects/arrays are not supported - deep-watching them would be too expensive
+returnfalse;
+}
+
+// fall-through to the primitive equality check
+}
+
+//Primitive or NaN
+returnnewValue===oldValueOfValue||(newValue!==newValue&&oldValueOfValue!==oldValueOfValue);
+}
+
+functioninputsWatchDelegate(scope,listener,objectEquality,parsedExpression){
+varinputExpressions=parsedExpression.$$inputs||
+(parsedExpression.$$inputs=collectExpressionInputs(parsedExpression.inputs,[]));
+
+varlastResult;
+
+if(inputExpressions.length===1){
+varoldInputValue=expressionInputDirtyCheck;// init to something unique so that equals check fails
+inputExpressions=inputExpressions[0];
+returnscope.$watch(functionexpressionInputWatch(scope){
+varnewInputValue=inputExpressions(scope);
+if(!expressionInputDirtyCheck(newInputValue,oldInputValue)){
+lastResult=parsedExpression(scope);
+oldInputValue=newInputValue&&newInputValue.valueOf();
+}
+returnlastResult;
+},listener,objectEquality);
+}
+
+varoldInputValueOfValues=[];
+for(vari=0,ii=inputExpressions.length;i<ii;i++){
+oldInputValueOfValues[i]=expressionInputDirtyCheck;// init to something unique so that equals check fails
+}
+
+returnscope.$watch(functionexpressionInputsWatch(scope){
+varchanged=false;
+
+for(vari=0,ii=inputExpressions.length;i<ii;i++){
+varnewInputValue=inputExpressions[i](scope);
+if(changed||(changed=!expressionInputDirtyCheck(newInputValue,oldInputValueOfValues[i]))){
+oldInputValueOfValues[i]=newInputValue&&newInputValue.valueOf();
+}
+}
+
+if(changed){
+lastResult=parsedExpression(scope);
+}
+
+returnlastResult;
+},listener,objectEquality);
+}
+
 functiononeTimeWatchDelegate(scope,listener,objectEquality,parsedExpression){
 varunwatch,lastValue;
 returnunwatch=scope.$watch(functiononeTimeWatch(scope){
@@ -1122,7 +1213,18 @@ function $ParseProvider() {
 // initial value is defined (for bind-once)
 returnisDefined(value) ? result : value;
 };
-fn.$$watchDelegate=parsedExpression.$$watchDelegate;
+
+// Propagate $$watchDelegates other then inputsWatchDelegate
+if(parsedExpression.$$watchDelegate&&
+parsedExpression.$$watchDelegate!==inputsWatchDelegate){
+fn.$$watchDelegate=parsedExpression.$$watchDelegate;
+}elseif(!interceptorFn.$stateful){
+// If there is an interceptor, but no watchDelegate then treat the interceptor like
+// we treat filters - it is assumed to be a pure function unless flagged with $stateful
+fn.$$watchDelegate=inputsWatchDelegate;
+fn.inputs=[parsedExpression];
+}
+
 returnfn;
 }
 }];

src/ng/rootScope.js

@@ -515,6 +515,8 @@ function $RootScopeProvider(){
  * de-registration function is executed, the internal watch operation is terminated.
  */
 $watchCollection: function(obj,listener){
+$watchCollectionInterceptor.$stateful=true;
+
 varself=this;
 // the current value, updated on each dirty-check run
 varnewValue;

test/ng/directive/ngRepeatSpec.js

@@ -867,12 +867,15 @@ describe('ngRepeat', function() {
 // This creates one item, but it has no parent so we can't get to it
 $rootScope.items=[1,2];
 $rootScope.$apply();
+expect(logs).toContain(1);
+expect(logs).toContain(2);
+logs.length=0;
 
 // This cleans up to prevent memory leak
 $rootScope.items=[];
 $rootScope.$apply();
 expect(angular.mock.dump(element)).toBe('<!-- ngRepeat: i in items -->');
-expect(logs).toEqual([1,2,1,2]);
+expect(logs.length).toBe(0);
 }));
 
 
@@ -894,12 +897,15 @@ describe('ngRepeat', function() {
 // This creates one item, but it has no parent so we can't get to it
 $rootScope.items=[1,2];
 $rootScope.$apply();
+expect(logs).toContain(1);
+expect(logs).toContain(2);
+logs.length=0;
 
 // This cleans up to prevent memory leak
 $rootScope.items=[];
 $rootScope.$apply();
 expect(sortedHtml(element)).toBe('<span>-</span><!-- ngRepeat: i in items --><span>-</span>');
-expect(logs).toEqual([1,2,1,2]);
+expect(logs.length).toBe(0);
 }));
 
 

benchmarks/parsed-expressions-bp/main.html

@@ -31,6 +31,11 @@
 <labelfor="operators">Binary/Unary operators</label>
 </li>
 
+<li>
+<inputtype="radio" ng-model="expressionType" value="shortCircuitingOperators" id="shortCircuitingOperators">
+<labelfor="shortCircuitingOperators">AND/OR short-circuiting operators</label>
+</li>
+
 <li>
 <inputtype="radio" ng-model="expressionType" value="filters" id="filters">
 <labelfor="filters">Filters</label>
@@ -134,6 +139,17 @@
 <spanbm-pe-watch="-rowIdx * 2 * rowIdx + rowIdx / rowIdx + 1"></span>
 </li>
 
+<ling-switch-when="shortCircuitingOperators" ng-repeat="(rowIdx, row) in ::data">
+<spanbm-pe-watch="rowIdx && row.odd"></span>
+<spanbm-pe-watch="row.odd && row.even"></span>
+<spanbm-pe-watch="row.odd && !row.even"></span>
+<spanbm-pe-watch="row.odd || row.even"></span>
+<spanbm-pe-watch="row.odd || row.even || row.index"></span>
+<spanbm-pe-watch="row.index === 1 || row.index === 2"></span>
+<spanbm-pe-watch="row.num0 < row.num1 && row.num1 < row.num2"></span>
+<spanbm-pe-watch="row.num0 < row.num1 || row.num1 < row.num2"></span>
+</li>
+
 <ling-switch-when="filters" ng-repeat="(rowIdx, row) in ::data">
 <spanbm-pe-watch="rowIdx | noop"></span>
 <spanbm-pe-watch="rowIdx | noop"></span>

src/ng/compile.js

@@ -1725,7 +1725,7 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
 attrs[attrName],newIsolateScopeDirective.name);
 };
 lastValue=isolateBindingContext[scopeName]=parentGet(scope);
-varunwatch=scope.$watch($parse(attrs[attrName],functionparentValueWatch(parentValue){
+varparentValueWatch=functionparentValueWatch(parentValue){
 if(!compare(parentValue,isolateBindingContext[scopeName])){
 // we are out of sync and need to copy
 if(!compare(parentValue,lastValue)){
@@ -1737,7 +1737,9 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
 }
 }
 returnlastValue=parentValue;
-}),null,parentGet.literal);
+};
+parentValueWatch.$stateful=true;
+varunwatch=scope.$watch($parse(attrs[attrName],parentValueWatch),null,parentGet.literal);
 isolateScope.$on('$destroy',unwatch);
 break;
 

src/ng/parse.js

@@ -376,6 +376,10 @@ Lexer.prototype = {
 };
 
 
+functionisConstant(exp){
+returnexp.constant;
+}
+
 /**
  * @constructor
  */
@@ -493,7 +497,8 @@ Parser.prototype = {
 returnextend(function(self,locals){
 returnfn(self,locals,right);
 },{
-constant:right.constant
+constant:right.constant,
+inputs: [right]
 });
 },
 
@@ -505,11 +510,12 @@ Parser.prototype = {
 });
 },
 
-binaryFn: function(left,fn,right){
+binaryFn: function(left,fn,right,isBranching){
 returnextend(function(self,locals){
 returnfn(self,locals,left,right);
 },{
-constant:left.constant&&right.constant
+constant: left.constant&&right.constant,
+inputs: !isBranching&&[left,right]
 });
 },
 
@@ -557,7 +563,9 @@ Parser.prototype = {
 }
 }
 
-returnfunction$parseFilter(self,locals){
+varinputs=[inputFn].concat(argsFn||[]);
+
+returnextend(function$parseFilter(self,locals){
 varinput=inputFn(self,locals);
 if(args){
 args[0]=input;
@@ -571,7 +579,10 @@ Parser.prototype = {
 }
 
 returnfn(input);
-};
+},{
+constant: !fn.$stateful&&inputs.every(isConstant),
+inputs: !fn.$stateful&&inputs
+});
 },
 
 expression: function(){
@@ -588,9 +599,11 @@ Parser.prototype = {
 this.text.substring(0,token.index)+'] can not be assigned to',token);
 }
 right=this.ternary();
-returnfunction$parseAssignment(scope,locals){
+returnextend(function$parseAssignment(scope,locals){
 returnleft.assign(scope,right(scope,locals),locals);
-};
+},{
+inputs: [left,right]
+});
 }
 returnleft;
 },
@@ -615,7 +628,7 @@ Parser.prototype = {
 varleft=this.logicalAND();
 vartoken;
 while((token=this.expect('||'))){
-left=this.binaryFn(left,token.fn,this.logicalAND());
+left=this.binaryFn(left,token.fn,this.logicalAND(),true);
 }
 returnleft;
 },
@@ -624,7 +637,7 @@ Parser.prototype = {
 varleft=this.equality();
 vartoken;
 if((token=this.expect('&&'))){
-left=this.binaryFn(left,token.fn,this.logicalAND());
+left=this.binaryFn(left,token.fn,this.logicalAND(),true);
 }
 returnleft;
 },
@@ -759,7 +772,6 @@ Parser.prototype = {
 // This is used with json array declaration
 arrayDeclaration: function(){
 varelementFns=[];
-varallConstant=true;
 if(this.peekToken().text!==']'){
 do{
 if(this.peek(']')){
@@ -768,9 +780,6 @@ Parser.prototype = {
 }
 varelementFn=this.expression();
 elementFns.push(elementFn);
-if(!elementFn.constant){
-allConstant=false;
-}
 }while(this.expect(','));
 }
 this.consume(']');
@@ -783,13 +792,13 @@ Parser.prototype = {
 returnarray;
 },{
 literal: true,
-constant: allConstant
+constant: elementFns.every(isConstant),
+inputs: elementFns
 });
 },
 
 object: function(){
 varkeys=[],valueFns=[];
-varallConstant=true;
 if(this.peekToken().text!=='}'){
 do{
 if(this.peek('}')){
@@ -801,9 +810,6 @@ Parser.prototype = {
 this.consume(':');
 varvalue=this.expression();
 valueFns.push(value);
-if(!value.constant){
-allConstant=false;
-}
 }while(this.expect(','));
 }
 this.consume('}');
@@ -816,7 +822,8 @@ Parser.prototype = {
 returnobject;
 },{
 literal: true,
-constant: allConstant
+constant: valueFns.every(isConstant),
+inputs: valueFns
 });
 }
 };
@@ -1043,6 +1050,8 @@ function $ParseProvider() {
 parsedExpression=wrapSharedExpression(parsedExpression);
 parsedExpression.$$watchDelegate=parsedExpression.literal ?
 oneTimeLiteralWatchDelegate : oneTimeWatchDelegate;
+}elseif(parsedExpression.inputs){
+parsedExpression.$$watchDelegate=inputsWatchDelegate;
 }
 
 cache[cacheKey]=parsedExpression;
@@ -1057,6 +1066,88 @@ function $ParseProvider() {
 }
 };
 
+functioncollectExpressionInputs(inputs,list){
+for(vari=0,ii=inputs.length;i<ii;i++){
+varinput=inputs[i];
+if(!input.constant){
+if(input.inputs){
+collectExpressionInputs(input.inputs,list);
+}elseif(list.indexOf(input)===-1){// TODO(perf) can we do better?
+list.push(input);
+}
+}
+}
+
+returnlist;
+}
+
+functionexpressionInputDirtyCheck(newValue,oldValueOfValue){
+
+if(newValue==null||oldValueOfValue==null){// null/undefined
+returnnewValue===oldValueOfValue;
+}
+
+if(typeofnewValue==='object'){
+
+// attempt to convert the value to a primitive type
+// TODO(docs): add a note to docs that by implementing valueOf even objects and arrays can
+// be cheaply dirty-checked
+newValue=newValue.valueOf();
+
+if(typeofnewValue==='object'){
+// objects/arrays are not supported - deep-watching them would be too expensive
+returnfalse;
+}
+
+// fall-through to the primitive equality check
+}
+
+//Primitive or NaN
+returnnewValue===oldValueOfValue||(newValue!==newValue&&oldValueOfValue!==oldValueOfValue);
+}
+
+functioninputsWatchDelegate(scope,listener,objectEquality,parsedExpression){
+varinputExpressions=parsedExpression.$$inputs||
+(parsedExpression.$$inputs=collectExpressionInputs(parsedExpression.inputs,[]));
+
+varlastResult;
+
+if(inputExpressions.length===1){
+varoldInputValue=expressionInputDirtyCheck;// init to something unique so that equals check fails
+inputExpressions=inputExpressions[0];
+returnscope.$watch(functionexpressionInputWatch(scope){
+varnewInputValue=inputExpressions(scope);
+if(!expressionInputDirtyCheck(newInputValue,oldInputValue)){
+lastResult=parsedExpression(scope);
+oldInputValue=newInputValue&&newInputValue.valueOf();
+}
+returnlastResult;
+},listener,objectEquality);
+}
+
+varoldInputValueOfValues=[];
+for(vari=0,ii=inputExpressions.length;i<ii;i++){
+oldInputValueOfValues[i]=expressionInputDirtyCheck;// init to something unique so that equals check fails
+}
+
+returnscope.$watch(functionexpressionInputsWatch(scope){
+varchanged=false;
+
+for(vari=0,ii=inputExpressions.length;i<ii;i++){
+varnewInputValue=inputExpressions[i](scope);
+if(changed||(changed=!expressionInputDirtyCheck(newInputValue,oldInputValueOfValues[i]))){
+oldInputValueOfValues[i]=newInputValue&&newInputValue.valueOf();
+}
+}
+
+if(changed){
+lastResult=parsedExpression(scope);
+}
+
+returnlastResult;
+},listener,objectEquality);
+}
+
 functiononeTimeWatchDelegate(scope,listener,objectEquality,parsedExpression){
 varunwatch,lastValue;
 returnunwatch=scope.$watch(functiononeTimeWatch(scope){
@@ -1122,7 +1213,18 @@ function $ParseProvider() {
 // initial value is defined (for bind-once)
 returnisDefined(value) ? result : value;
 };
-fn.$$watchDelegate=parsedExpression.$$watchDelegate;
+
+// Propagate $$watchDelegates other then inputsWatchDelegate
+if(parsedExpression.$$watchDelegate&&
+parsedExpression.$$watchDelegate!==inputsWatchDelegate){
+fn.$$watchDelegate=parsedExpression.$$watchDelegate;
+}elseif(!interceptorFn.$stateful){
+// If there is an interceptor, but no watchDelegate then treat the interceptor like
+// we treat filters - it is assumed to be a pure function unless flagged with $stateful
+fn.$$watchDelegate=inputsWatchDelegate;
+fn.inputs=[parsedExpression];
+}
+
 returnfn;
 }
 }];

src/ng/rootScope.js

@@ -515,6 +515,8 @@ function $RootScopeProvider(){
  * de-registration function is executed, the internal watch operation is terminated.
  */
 $watchCollection: function(obj,listener){
+$watchCollectionInterceptor.$stateful=true;
+
 varself=this;
 // the current value, updated on each dirty-check run
 varnewValue;

test/ng/directive/ngRepeatSpec.js

@@ -867,12 +867,15 @@ describe('ngRepeat', function() {
 // This creates one item, but it has no parent so we can't get to it
 $rootScope.items=[1,2];
 $rootScope.$apply();
+expect(logs).toContain(1);
+expect(logs).toContain(2);
+logs.length=0;
 
 // This cleans up to prevent memory leak
 $rootScope.items=[];
 $rootScope.$apply();
 expect(angular.mock.dump(element)).toBe('<!-- ngRepeat: i in items -->');
-expect(logs).toEqual([1,2,1,2]);
+expect(logs.length).toBe(0);
 }));
 
 
@@ -894,12 +897,15 @@ describe('ngRepeat', function() {
 // This creates one item, but it has no parent so we can't get to it
 $rootScope.items=[1,2];
 $rootScope.$apply();
+expect(logs).toContain(1);
+expect(logs).toContain(2);
+logs.length=0;
 
 // This cleans up to prevent memory leak
 $rootScope.items=[];
 $rootScope.$apply();
 expect(sortedHtml(element)).toBe('<span>-</span><!-- ngRepeat: i in items --><span>-</span>');
-expect(logs).toEqual([1,2,1,2]);
+expect(logs.length).toBe(0);
 }));
 
 

benchmarks/parsed-expressions-bp/main.html

@@ -31,6 +31,11 @@
 <labelfor="operators">Binary/Unary operators</label>
 </li>
 
+<li>
+<inputtype="radio" ng-model="expressionType" value="shortCircuitingOperators" id="shortCircuitingOperators">
+<labelfor="shortCircuitingOperators">AND/OR short-circuiting operators</label>
+</li>
+
 <li>
 <inputtype="radio" ng-model="expressionType" value="filters" id="filters">
 <labelfor="filters">Filters</label>
@@ -134,6 +139,17 @@
 <spanbm-pe-watch="-rowIdx * 2 * rowIdx + rowIdx / rowIdx + 1"></span>
 </li>
 
+<ling-switch-when="shortCircuitingOperators" ng-repeat="(rowIdx, row) in ::data">
+<spanbm-pe-watch="rowIdx && row.odd"></span>
+<spanbm-pe-watch="row.odd && row.even"></span>
+<spanbm-pe-watch="row.odd && !row.even"></span>
+<spanbm-pe-watch="row.odd || row.even"></span>
+<spanbm-pe-watch="row.odd || row.even || row.index"></span>
+<spanbm-pe-watch="row.index === 1 || row.index === 2"></span>
+<spanbm-pe-watch="row.num0 < row.num1 && row.num1 < row.num2"></span>
+<spanbm-pe-watch="row.num0 < row.num1 || row.num1 < row.num2"></span>
+</li>
+
 <ling-switch-when="filters" ng-repeat="(rowIdx, row) in ::data">
 <spanbm-pe-watch="rowIdx | noop"></span>
 <spanbm-pe-watch="rowIdx | noop"></span>

src/ng/compile.js

@@ -1725,7 +1725,7 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
 attrs[attrName],newIsolateScopeDirective.name);
 };
 lastValue=isolateBindingContext[scopeName]=parentGet(scope);
-varunwatch=scope.$watch($parse(attrs[attrName],functionparentValueWatch(parentValue){
+varparentValueWatch=functionparentValueWatch(parentValue){
 if(!compare(parentValue,isolateBindingContext[scopeName])){
 // we are out of sync and need to copy
 if(!compare(parentValue,lastValue)){
@@ -1737,7 +1737,9 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
 }
 }
 returnlastValue=parentValue;
-}),null,parentGet.literal);
+};
+parentValueWatch.$stateful=true;
+varunwatch=scope.$watch($parse(attrs[attrName],parentValueWatch),null,parentGet.literal);
 isolateScope.$on('$destroy',unwatch);
 break;
 

src/ng/parse.js

@@ -376,6 +376,10 @@ Lexer.prototype = {
 };
 
 
+functionisConstant(exp){
+returnexp.constant;
+}
+
 /**
  * @constructor
  */
@@ -493,7 +497,8 @@ Parser.prototype = {
 returnextend(function(self,locals){
 returnfn(self,locals,right);
 },{
-constant:right.constant
+constant:right.constant,
+inputs: [right]
 });
 },
 
@@ -505,11 +510,12 @@ Parser.prototype = {
 });
 },
 
-binaryFn: function(left,fn,right){
+binaryFn: function(left,fn,right,isBranching){
 returnextend(function(self,locals){
 returnfn(self,locals,left,right);
 },{
-constant:left.constant&&right.constant
+constant: left.constant&&right.constant,
+inputs: !isBranching&&[left,right]
 });
 },
 
@@ -557,7 +563,9 @@ Parser.prototype = {
 }
 }
 
-returnfunction$parseFilter(self,locals){
+varinputs=[inputFn].concat(argsFn||[]);
+
+returnextend(function$parseFilter(self,locals){
 varinput=inputFn(self,locals);
 if(args){
 args[0]=input;
@@ -571,7 +579,10 @@ Parser.prototype = {
 }
 
 returnfn(input);
-};
+},{
+constant: !fn.$stateful&&inputs.every(isConstant),
+inputs: !fn.$stateful&&inputs
+});
 },
 
 expression: function(){
@@ -588,9 +599,11 @@ Parser.prototype = {
 this.text.substring(0,token.index)+'] can not be assigned to',token);
 }
 right=this.ternary();
-returnfunction$parseAssignment(scope,locals){
+returnextend(function$parseAssignment(scope,locals){
 returnleft.assign(scope,right(scope,locals),locals);
-};
+},{
+inputs: [left,right]
+});
 }
 returnleft;
 },
@@ -615,7 +628,7 @@ Parser.prototype = {
 varleft=this.logicalAND();
 vartoken;
 while((token=this.expect('||'))){
-left=this.binaryFn(left,token.fn,this.logicalAND());
+left=this.binaryFn(left,token.fn,this.logicalAND(),true);
 }
 returnleft;
 },
@@ -624,7 +637,7 @@ Parser.prototype = {
 varleft=this.equality();
 vartoken;
 if((token=this.expect('&&'))){
-left=this.binaryFn(left,token.fn,this.logicalAND());
+left=this.binaryFn(left,token.fn,this.logicalAND(),true);
 }
 returnleft;
 },
@@ -759,7 +772,6 @@ Parser.prototype = {
 // This is used with json array declaration
 arrayDeclaration: function(){
 varelementFns=[];
-varallConstant=true;
 if(this.peekToken().text!==']'){
 do{
 if(this.peek(']')){
@@ -768,9 +780,6 @@ Parser.prototype = {
 }
 varelementFn=this.expression();
 elementFns.push(elementFn);
-if(!elementFn.constant){
-allConstant=false;
-}
 }while(this.expect(','));
 }
 this.consume(']');
@@ -783,13 +792,13 @@ Parser.prototype = {
 returnarray;
 },{
 literal: true,
-constant: allConstant
+constant: elementFns.every(isConstant),
+inputs: elementFns
 });
 },
 
 object: function(){
 varkeys=[],valueFns=[];
-varallConstant=true;
 if(this.peekToken().text!=='}'){
 do{
 if(this.peek('}')){
@@ -801,9 +810,6 @@ Parser.prototype = {
 this.consume(':');
 varvalue=this.expression();
 valueFns.push(value);
-if(!value.constant){
-allConstant=false;
-}
 }while(this.expect(','));
 }
 this.consume('}');
@@ -816,7 +822,8 @@ Parser.prototype = {
 returnobject;
 },{
 literal: true,
-constant: allConstant
+constant: valueFns.every(isConstant),
+inputs: valueFns
 });
 }
 };
@@ -1043,6 +1050,8 @@ function $ParseProvider() {
 parsedExpression=wrapSharedExpression(parsedExpression);
 parsedExpression.$$watchDelegate=parsedExpression.literal ?
 oneTimeLiteralWatchDelegate : oneTimeWatchDelegate;
+}elseif(parsedExpression.inputs){
+parsedExpression.$$watchDelegate=inputsWatchDelegate;
 }
 
 cache[cacheKey]=parsedExpression;
@@ -1057,6 +1066,88 @@ function $ParseProvider() {
 }
 };
 
+functioncollectExpressionInputs(inputs,list){
+for(vari=0,ii=inputs.length;i<ii;i++){
+varinput=inputs[i];
+if(!input.constant){
+if(input.inputs){
+collectExpressionInputs(input.inputs,list);
+}elseif(list.indexOf(input)===-1){// TODO(perf) can we do better?
+list.push(input);
+}
+}
+}
+
+returnlist;
+}
+
+functionexpressionInputDirtyCheck(newValue,oldValueOfValue){
+
+if(newValue==null||oldValueOfValue==null){// null/undefined
+returnnewValue===oldValueOfValue;
+}
+
+if(typeofnewValue==='object'){
+
+// attempt to convert the value to a primitive type
+// TODO(docs): add a note to docs that by implementing valueOf even objects and arrays can
+// be cheaply dirty-checked
+newValue=newValue.valueOf();
+
+if(typeofnewValue==='object'){
+// objects/arrays are not supported - deep-watching them would be too expensive
+returnfalse;
+}
+
+// fall-through to the primitive equality check
+}
+
+//Primitive or NaN
+returnnewValue===oldValueOfValue||(newValue!==newValue&&oldValueOfValue!==oldValueOfValue);
+}
+
+functioninputsWatchDelegate(scope,listener,objectEquality,parsedExpression){
+varinputExpressions=parsedExpression.$$inputs||
+(parsedExpression.$$inputs=collectExpressionInputs(parsedExpression.inputs,[]));
+
+varlastResult;
+
+if(inputExpressions.length===1){
+varoldInputValue=expressionInputDirtyCheck;// init to something unique so that equals check fails
+inputExpressions=inputExpressions[0];
+returnscope.$watch(functionexpressionInputWatch(scope){
+varnewInputValue=inputExpressions(scope);
+if(!expressionInputDirtyCheck(newInputValue,oldInputValue)){
+lastResult=parsedExpression(scope);
+oldInputValue=newInputValue&&newInputValue.valueOf();
+}
+returnlastResult;
+},listener,objectEquality);
+}
+
+varoldInputValueOfValues=[];
+for(vari=0,ii=inputExpressions.length;i<ii;i++){
+oldInputValueOfValues[i]=expressionInputDirtyCheck;// init to something unique so that equals check fails
+}
+
+returnscope.$watch(functionexpressionInputsWatch(scope){
+varchanged=false;
+
+for(vari=0,ii=inputExpressions.length;i<ii;i++){
+varnewInputValue=inputExpressions[i](scope);
+if(changed||(changed=!expressionInputDirtyCheck(newInputValue,oldInputValueOfValues[i]))){
+oldInputValueOfValues[i]=newInputValue&&newInputValue.valueOf();
+}
+}
+
+if(changed){
+lastResult=parsedExpression(scope);
+}
+
+returnlastResult;
+},listener,objectEquality);
+}
+
 functiononeTimeWatchDelegate(scope,listener,objectEquality,parsedExpression){
 varunwatch,lastValue;
 returnunwatch=scope.$watch(functiononeTimeWatch(scope){
@@ -1122,7 +1213,18 @@ function $ParseProvider() {
 // initial value is defined (for bind-once)
 returnisDefined(value) ? result : value;
 };
-fn.$$watchDelegate=parsedExpression.$$watchDelegate;
+
+// Propagate $$watchDelegates other then inputsWatchDelegate
+if(parsedExpression.$$watchDelegate&&
+parsedExpression.$$watchDelegate!==inputsWatchDelegate){
+fn.$$watchDelegate=parsedExpression.$$watchDelegate;
+}elseif(!interceptorFn.$stateful){
+// If there is an interceptor, but no watchDelegate then treat the interceptor like
+// we treat filters - it is assumed to be a pure function unless flagged with $stateful
+fn.$$watchDelegate=inputsWatchDelegate;
+fn.inputs=[parsedExpression];
+}
+
 returnfn;
 }
 }];

src/ng/rootScope.js

@@ -515,6 +515,8 @@ function $RootScopeProvider(){
  * de-registration function is executed, the internal watch operation is terminated.
  */
 $watchCollection: function(obj,listener){
+$watchCollectionInterceptor.$stateful=true;
+
 varself=this;
 // the current value, updated on each dirty-check run
 varnewValue;

test/ng/directive/ngRepeatSpec.js

@@ -867,12 +867,15 @@ describe('ngRepeat', function() {
 // This creates one item, but it has no parent so we can't get to it
 $rootScope.items=[1,2];
 $rootScope.$apply();
+expect(logs).toContain(1);
+expect(logs).toContain(2);
+logs.length=0;
 
 // This cleans up to prevent memory leak
 $rootScope.items=[];
 $rootScope.$apply();
 expect(angular.mock.dump(element)).toBe('<!-- ngRepeat: i in items -->');
-expect(logs).toEqual([1,2,1,2]);
+expect(logs.length).toBe(0);
 }));
 
 
@@ -894,12 +897,15 @@ describe('ngRepeat', function() {
 // This creates one item, but it has no parent so we can't get to it
 $rootScope.items=[1,2];
 $rootScope.$apply();
+expect(logs).toContain(1);
+expect(logs).toContain(2);
+logs.length=0;
 
 // This cleans up to prevent memory leak
 $rootScope.items=[];
 $rootScope.$apply();
 expect(sortedHtml(element)).toBe('<span>-</span><!-- ngRepeat: i in items --><span>-</span>');
-expect(logs).toEqual([1,2,1,2]);
+expect(logs.length).toBe(0);
 }));
 
 

benchmarks/parsed-expressions-bp/main.html

@@ -31,6 +31,11 @@
 <labelfor="operators">Binary/Unary operators</label>
 </li>
 
+<li>
+<inputtype="radio" ng-model="expressionType" value="shortCircuitingOperators" id="shortCircuitingOperators">
+<labelfor="shortCircuitingOperators">AND/OR short-circuiting operators</label>
+</li>
+
 <li>
 <inputtype="radio" ng-model="expressionType" value="filters" id="filters">
 <labelfor="filters">Filters</label>
@@ -134,6 +139,17 @@
 <spanbm-pe-watch="-rowIdx * 2 * rowIdx + rowIdx / rowIdx + 1"></span>
 </li>
 
+<ling-switch-when="shortCircuitingOperators" ng-repeat="(rowIdx, row) in ::data">
+<spanbm-pe-watch="rowIdx && row.odd"></span>
+<spanbm-pe-watch="row.odd && row.even"></span>
+<spanbm-pe-watch="row.odd && !row.even"></span>
+<spanbm-pe-watch="row.odd || row.even"></span>
+<spanbm-pe-watch="row.odd || row.even || row.index"></span>
+<spanbm-pe-watch="row.index === 1 || row.index === 2"></span>
+<spanbm-pe-watch="row.num0 < row.num1 && row.num1 < row.num2"></span>
+<spanbm-pe-watch="row.num0 < row.num1 || row.num1 < row.num2"></span>
+</li>
+
 <ling-switch-when="filters" ng-repeat="(rowIdx, row) in ::data">
 <spanbm-pe-watch="rowIdx | noop"></span>
 <spanbm-pe-watch="rowIdx | noop"></span>

src/ng/compile.js

@@ -1725,7 +1725,7 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
 attrs[attrName],newIsolateScopeDirective.name);
 };
 lastValue=isolateBindingContext[scopeName]=parentGet(scope);
-varunwatch=scope.$watch($parse(attrs[attrName],functionparentValueWatch(parentValue){
+varparentValueWatch=functionparentValueWatch(parentValue){
 if(!compare(parentValue,isolateBindingContext[scopeName])){
 // we are out of sync and need to copy
 if(!compare(parentValue,lastValue)){
@@ -1737,7 +1737,9 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
 }
 }
 returnlastValue=parentValue;
-}),null,parentGet.literal);
+};
+parentValueWatch.$stateful=true;
+varunwatch=scope.$watch($parse(attrs[attrName],parentValueWatch),null,parentGet.literal);
 isolateScope.$on('$destroy',unwatch);
 break;
 

src/ng/parse.js

@@ -376,6 +376,10 @@ Lexer.prototype = {
 };
 
 
+functionisConstant(exp){
+returnexp.constant;
+}
+
 /**
  * @constructor
  */
@@ -493,7 +497,8 @@ Parser.prototype = {
 returnextend(function(self,locals){
 returnfn(self,locals,right);
 },{
-constant:right.constant
+constant:right.constant,
+inputs: [right]
 });
 },
 
@@ -505,11 +510,12 @@ Parser.prototype = {
 });
 },
 
-binaryFn: function(left,fn,right){
+binaryFn: function(left,fn,right,isBranching){
 returnextend(function(self,locals){
 returnfn(self,locals,left,right);
 },{
-constant:left.constant&&right.constant
+constant: left.constant&&right.constant,
+inputs: !isBranching&&[left,right]
 });
 },
 
@@ -557,7 +563,9 @@ Parser.prototype = {
 }
 }
 
-returnfunction$parseFilter(self,locals){
+varinputs=[inputFn].concat(argsFn||[]);
+
+returnextend(function$parseFilter(self,locals){
 varinput=inputFn(self,locals);
 if(args){
 args[0]=input;
@@ -571,7 +579,10 @@ Parser.prototype = {
 }
 
 returnfn(input);
-};
+},{
+constant: !fn.$stateful&&inputs.every(isConstant),
+inputs: !fn.$stateful&&inputs
+});
 },
 
 expression: function(){
@@ -588,9 +599,11 @@ Parser.prototype = {
 this.text.substring(0,token.index)+'] can not be assigned to',token);
 }
 right=this.ternary();
-returnfunction$parseAssignment(scope,locals){
+returnextend(function$parseAssignment(scope,locals){
 returnleft.assign(scope,right(scope,locals),locals);
-};
+},{
+inputs: [left,right]
+});
 }
 returnleft;
 },
@@ -615,7 +628,7 @@ Parser.prototype = {
 varleft=this.logicalAND();
 vartoken;
 while((token=this.expect('||'))){
-left=this.binaryFn(left,token.fn,this.logicalAND());
+left=this.binaryFn(left,token.fn,this.logicalAND(),true);
 }
 returnleft;
 },
@@ -624,7 +637,7 @@ Parser.prototype = {
 varleft=this.equality();
 vartoken;
 if((token=this.expect('&&'))){
-left=this.binaryFn(left,token.fn,this.logicalAND());
+left=this.binaryFn(left,token.fn,this.logicalAND(),true);
 }
 returnleft;
 },
@@ -759,7 +772,6 @@ Parser.prototype = {
 // This is used with json array declaration
 arrayDeclaration: function(){
 varelementFns=[];
-varallConstant=true;
 if(this.peekToken().text!==']'){
 do{
 if(this.peek(']')){
@@ -768,9 +780,6 @@ Parser.prototype = {
 }
 varelementFn=this.expression();
 elementFns.push(elementFn);
-if(!elementFn.constant){
-allConstant=false;
-}
 }while(this.expect(','));
 }
 this.consume(']');
@@ -783,13 +792,13 @@ Parser.prototype = {
 returnarray;
 },{
 literal: true,
-constant: allConstant
+constant: elementFns.every(isConstant),
+inputs: elementFns
 });
 },
 
 object: function(){
 varkeys=[],valueFns=[];
-varallConstant=true;
 if(this.peekToken().text!=='}'){
 do{
 if(this.peek('}')){
@@ -801,9 +810,6 @@ Parser.prototype = {
 this.consume(':');
 varvalue=this.expression();
 valueFns.push(value);
-if(!value.constant){
-allConstant=false;
-}
 }while(this.expect(','));
 }
 this.consume('}');
@@ -816,7 +822,8 @@ Parser.prototype = {
 returnobject;
 },{
 literal: true,
-constant: allConstant
+constant: valueFns.every(isConstant),
+inputs: valueFns
 });
 }
 };
@@ -1043,6 +1050,8 @@ function $ParseProvider() {
 parsedExpression=wrapSharedExpression(parsedExpression);
 parsedExpression.$$watchDelegate=parsedExpression.literal ?
 oneTimeLiteralWatchDelegate : oneTimeWatchDelegate;
+}elseif(parsedExpression.inputs){
+parsedExpression.$$watchDelegate=inputsWatchDelegate;
 }
 
 cache[cacheKey]=parsedExpression;
@@ -1057,6 +1066,88 @@ function $ParseProvider() {
 }
 };
 
+functioncollectExpressionInputs(inputs,list){
+for(vari=0,ii=inputs.length;i<ii;i++){
+varinput=inputs[i];
+if(!input.constant){
+if(input.inputs){
+collectExpressionInputs(input.inputs,list);
+}elseif(list.indexOf(input)===-1){// TODO(perf) can we do better?
+list.push(input);
+}
+}
+}
+
+returnlist;
+}
+
+functionexpressionInputDirtyCheck(newValue,oldValueOfValue){
+
+if(newValue==null||oldValueOfValue==null){// null/undefined
+returnnewValue===oldValueOfValue;
+}
+
+if(typeofnewValue==='object'){
+
+// attempt to convert the value to a primitive type
+// TODO(docs): add a note to docs that by implementing valueOf even objects and arrays can
+// be cheaply dirty-checked
+newValue=newValue.valueOf();
+
+if(typeofnewValue==='object'){
+// objects/arrays are not supported - deep-watching them would be too expensive
+returnfalse;
+}
+
+// fall-through to the primitive equality check
+}
+
+//Primitive or NaN
+returnnewValue===oldValueOfValue||(newValue!==newValue&&oldValueOfValue!==oldValueOfValue);
+}
+
+functioninputsWatchDelegate(scope,listener,objectEquality,parsedExpression){
+varinputExpressions=parsedExpression.$$inputs||
+(parsedExpression.$$inputs=collectExpressionInputs(parsedExpression.inputs,[]));
+
+varlastResult;
+
+if(inputExpressions.length===1){
+varoldInputValue=expressionInputDirtyCheck;// init to something unique so that equals check fails
+inputExpressions=inputExpressions[0];
+returnscope.$watch(functionexpressionInputWatch(scope){
+varnewInputValue=inputExpressions(scope);
+if(!expressionInputDirtyCheck(newInputValue,oldInputValue)){
+lastResult=parsedExpression(scope);
+oldInputValue=newInputValue&&newInputValue.valueOf();
+}
+returnlastResult;
+},listener,objectEquality);
+}
+
+varoldInputValueOfValues=[];
+for(vari=0,ii=inputExpressions.length;i<ii;i++){
+oldInputValueOfValues[i]=expressionInputDirtyCheck;// init to something unique so that equals check fails
+}
+
+returnscope.$watch(functionexpressionInputsWatch(scope){
+varchanged=false;
+
+for(vari=0,ii=inputExpressions.length;i<ii;i++){
+varnewInputValue=inputExpressions[i](scope);
+if(changed||(changed=!expressionInputDirtyCheck(newInputValue,oldInputValueOfValues[i]))){
+oldInputValueOfValues[i]=newInputValue&&newInputValue.valueOf();
+}
+}
+
+if(changed){
+lastResult=parsedExpression(scope);
+}
+
+returnlastResult;
+},listener,objectEquality);
+}
+
 functiononeTimeWatchDelegate(scope,listener,objectEquality,parsedExpression){
 varunwatch,lastValue;
 returnunwatch=scope.$watch(functiononeTimeWatch(scope){
@@ -1122,7 +1213,18 @@ function $ParseProvider() {
 // initial value is defined (for bind-once)
 returnisDefined(value) ? result : value;
 };
-fn.$$watchDelegate=parsedExpression.$$watchDelegate;
+
+// Propagate $$watchDelegates other then inputsWatchDelegate
+if(parsedExpression.$$watchDelegate&&
+parsedExpression.$$watchDelegate!==inputsWatchDelegate){
+fn.$$watchDelegate=parsedExpression.$$watchDelegate;
+}elseif(!interceptorFn.$stateful){
+// If there is an interceptor, but no watchDelegate then treat the interceptor like
+// we treat filters - it is assumed to be a pure function unless flagged with $stateful
+fn.$$watchDelegate=inputsWatchDelegate;
+fn.inputs=[parsedExpression];
+}
+
 returnfn;
 }
 }];

src/ng/rootScope.js

@@ -515,6 +515,8 @@ function $RootScopeProvider(){
  * de-registration function is executed, the internal watch operation is terminated.
  */
 $watchCollection: function(obj,listener){
+$watchCollectionInterceptor.$stateful=true;
+
 varself=this;
 // the current value, updated on each dirty-check run
 varnewValue;

test/ng/directive/ngRepeatSpec.js

@@ -867,12 +867,15 @@ describe('ngRepeat', function() {
 // This creates one item, but it has no parent so we can't get to it
 $rootScope.items=[1,2];
 $rootScope.$apply();
+expect(logs).toContain(1);
+expect(logs).toContain(2);
+logs.length=0;
 
 // This cleans up to prevent memory leak
 $rootScope.items=[];
 $rootScope.$apply();
 expect(angular.mock.dump(element)).toBe('<!-- ngRepeat: i in items -->');
-expect(logs).toEqual([1,2,1,2]);
+expect(logs.length).toBe(0);
 }));
 
 
@@ -894,12 +897,15 @@ describe('ngRepeat', function() {
 // This creates one item, but it has no parent so we can't get to it
 $rootScope.items=[1,2];
 $rootScope.$apply();
+expect(logs).toContain(1);
+expect(logs).toContain(2);
+logs.length=0;
 
 // This cleans up to prevent memory leak
 $rootScope.items=[];
 $rootScope.$apply();
 expect(sortedHtml(element)).toBe('<span>-</span><!-- ngRepeat: i in items --><span>-</span>');
-expect(logs).toEqual([1,2,1,2]);
+expect(logs.length).toBe(0);
 }));
 
 

benchmarks/parsed-expressions-bp/main.html

@@ -31,6 +31,11 @@
 <labelfor="operators">Binary/Unary operators</label>
 </li>
 
+<li>
+<inputtype="radio" ng-model="expressionType" value="shortCircuitingOperators" id="shortCircuitingOperators">
+<labelfor="shortCircuitingOperators">AND/OR short-circuiting operators</label>
+</li>
+
 <li>
 <inputtype="radio" ng-model="expressionType" value="filters" id="filters">
 <labelfor="filters">Filters</label>
@@ -134,6 +139,17 @@
 <spanbm-pe-watch="-rowIdx * 2 * rowIdx + rowIdx / rowIdx + 1"></span>
 </li>
 
+<ling-switch-when="shortCircuitingOperators" ng-repeat="(rowIdx, row) in ::data">
+<spanbm-pe-watch="rowIdx && row.odd"></span>
+<spanbm-pe-watch="row.odd && row.even"></span>
+<spanbm-pe-watch="row.odd && !row.even"></span>
+<spanbm-pe-watch="row.odd || row.even"></span>
+<spanbm-pe-watch="row.odd || row.even || row.index"></span>
+<spanbm-pe-watch="row.index === 1 || row.index === 2"></span>
+<spanbm-pe-watch="row.num0 < row.num1 && row.num1 < row.num2"></span>
+<spanbm-pe-watch="row.num0 < row.num1 || row.num1 < row.num2"></span>
+</li>
+
 <ling-switch-when="filters" ng-repeat="(rowIdx, row) in ::data">
 <spanbm-pe-watch="rowIdx | noop"></span>
 <spanbm-pe-watch="rowIdx | noop"></span>

src/ng/compile.js

@@ -1725,7 +1725,7 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
 attrs[attrName],newIsolateScopeDirective.name);
 };
 lastValue=isolateBindingContext[scopeName]=parentGet(scope);
-varunwatch=scope.$watch($parse(attrs[attrName],functionparentValueWatch(parentValue){
+varparentValueWatch=functionparentValueWatch(parentValue){
 if(!compare(parentValue,isolateBindingContext[scopeName])){
 // we are out of sync and need to copy
 if(!compare(parentValue,lastValue)){
@@ -1737,7 +1737,9 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
 }
 }
 returnlastValue=parentValue;
-}),null,parentGet.literal);
+};
+parentValueWatch.$stateful=true;
+varunwatch=scope.$watch($parse(attrs[attrName],parentValueWatch),null,parentGet.literal);
 isolateScope.$on('$destroy',unwatch);
 break;
 

src/ng/parse.js

@@ -376,6 +376,10 @@ Lexer.prototype = {
 };
 
 
+functionisConstant(exp){
+returnexp.constant;
+}
+
 /**
  * @constructor
  */
@@ -493,7 +497,8 @@ Parser.prototype = {
 returnextend(function(self,locals){
 returnfn(self,locals,right);
 },{
-constant:right.constant
+constant:right.constant,
+inputs: [right]
 });
 },
 
@@ -505,11 +510,12 @@ Parser.prototype = {
 });
 },
 
-binaryFn: function(left,fn,right){
+binaryFn: function(left,fn,right,isBranching){
 returnextend(function(self,locals){
 returnfn(self,locals,left,right);
 },{
-constant:left.constant&&right.constant
+constant: left.constant&&right.constant,
+inputs: !isBranching&&[left,right]
 });
 },
 
@@ -557,7 +563,9 @@ Parser.prototype = {
 }
 }
 
-returnfunction$parseFilter(self,locals){
+varinputs=[inputFn].concat(argsFn||[]);
+
+returnextend(function$parseFilter(self,locals){
 varinput=inputFn(self,locals);
 if(args){
 args[0]=input;
@@ -571,7 +579,10 @@ Parser.prototype = {
 }
 
 returnfn(input);
-};
+},{
+constant: !fn.$stateful&&inputs.every(isConstant),
+inputs: !fn.$stateful&&inputs
+});
 },
 
 expression: function(){
@@ -588,9 +599,11 @@ Parser.prototype = {
 this.text.substring(0,token.index)+'] can not be assigned to',token);
 }
 right=this.ternary();
-returnfunction$parseAssignment(scope,locals){
+returnextend(function$parseAssignment(scope,locals){
 returnleft.assign(scope,right(scope,locals),locals);
-};
+},{
+inputs: [left,right]
+});
 }
 returnleft;
 },
@@ -615,7 +628,7 @@ Parser.prototype = {
 varleft=this.logicalAND();
 vartoken;
 while((token=this.expect('||'))){
-left=this.binaryFn(left,token.fn,this.logicalAND());
+left=this.binaryFn(left,token.fn,this.logicalAND(),true);
 }
 returnleft;
 },
@@ -624,7 +637,7 @@ Parser.prototype = {
 varleft=this.equality();
 vartoken;
 if((token=this.expect('&&'))){
-left=this.binaryFn(left,token.fn,this.logicalAND());
+left=this.binaryFn(left,token.fn,this.logicalAND(),true);
 }
 returnleft;
 },
@@ -759,7 +772,6 @@ Parser.prototype = {
 // This is used with json array declaration
 arrayDeclaration: function(){
 varelementFns=[];
-varallConstant=true;
 if(this.peekToken().text!==']'){
 do{
 if(this.peek(']')){
@@ -768,9 +780,6 @@ Parser.prototype = {
 }
 varelementFn=this.expression();
 elementFns.push(elementFn);
-if(!elementFn.constant){
-allConstant=false;
-}
 }while(this.expect(','));
 }
 this.consume(']');
@@ -783,13 +792,13 @@ Parser.prototype = {
 returnarray;
 },{
 literal: true,
-constant: allConstant
+constant: elementFns.every(isConstant),
+inputs: elementFns
 });
 },
 
 object: function(){
 varkeys=[],valueFns=[];
-varallConstant=true;
 if(this.peekToken().text!=='}'){
 do{
 if(this.peek('}')){
@@ -801,9 +810,6 @@ Parser.prototype = {
 this.consume(':');
 varvalue=this.expression();
 valueFns.push(value);
-if(!value.constant){
-allConstant=false;
-}
 }while(this.expect(','));
 }
 this.consume('}');
@@ -816,7 +822,8 @@ Parser.prototype = {
 returnobject;
 },{
 literal: true,
-constant: allConstant
+constant: valueFns.every(isConstant),
+inputs: valueFns
 });
 }
 };
@@ -1043,6 +1050,8 @@ function $ParseProvider() {
 parsedExpression=wrapSharedExpression(parsedExpression);
 parsedExpression.$$watchDelegate=parsedExpression.literal ?
 oneTimeLiteralWatchDelegate : oneTimeWatchDelegate;
+}elseif(parsedExpression.inputs){
+parsedExpression.$$watchDelegate=inputsWatchDelegate;
 }
 
 cache[cacheKey]=parsedExpression;
@@ -1057,6 +1066,88 @@ function $ParseProvider() {
 }
 };
 
+functioncollectExpressionInputs(inputs,list){
+for(vari=0,ii=inputs.length;i<ii;i++){
+varinput=inputs[i];
+if(!input.constant){
+if(input.inputs){
+collectExpressionInputs(input.inputs,list);
+}elseif(list.indexOf(input)===-1){// TODO(perf) can we do better?
+list.push(input);
+}
+}
+}
+
+returnlist;
+}
+
+functionexpressionInputDirtyCheck(newValue,oldValueOfValue){
+
+if(newValue==null||oldValueOfValue==null){// null/undefined
+returnnewValue===oldValueOfValue;
+}
+
+if(typeofnewValue==='object'){
+
+// attempt to convert the value to a primitive type
+// TODO(docs): add a note to docs that by implementing valueOf even objects and arrays can
+// be cheaply dirty-checked
+newValue=newValue.valueOf();
+
+if(typeofnewValue==='object'){
+// objects/arrays are not supported - deep-watching them would be too expensive
+returnfalse;
+}
+
+// fall-through to the primitive equality check
+}
+
+//Primitive or NaN
+returnnewValue===oldValueOfValue||(newValue!==newValue&&oldValueOfValue!==oldValueOfValue);
+}
+
+functioninputsWatchDelegate(scope,listener,objectEquality,parsedExpression){
+varinputExpressions=parsedExpression.$$inputs||
+(parsedExpression.$$inputs=collectExpressionInputs(parsedExpression.inputs,[]));
+
+varlastResult;
+
+if(inputExpressions.length===1){
+varoldInputValue=expressionInputDirtyCheck;// init to something unique so that equals check fails
+inputExpressions=inputExpressions[0];
+returnscope.$watch(functionexpressionInputWatch(scope){
+varnewInputValue=inputExpressions(scope);
+if(!expressionInputDirtyCheck(newInputValue,oldInputValue)){
+lastResult=parsedExpression(scope);
+oldInputValue=newInputValue&&newInputValue.valueOf();
+}
+returnlastResult;
+},listener,objectEquality);
+}
+
+varoldInputValueOfValues=[];
+for(vari=0,ii=inputExpressions.length;i<ii;i++){
+oldInputValueOfValues[i]=expressionInputDirtyCheck;// init to something unique so that equals check fails
+}
+
+returnscope.$watch(functionexpressionInputsWatch(scope){
+varchanged=false;
+
+for(vari=0,ii=inputExpressions.length;i<ii;i++){
+varnewInputValue=inputExpressions[i](scope);
+if(changed||(changed=!expressionInputDirtyCheck(newInputValue,oldInputValueOfValues[i]))){
+oldInputValueOfValues[i]=newInputValue&&newInputValue.valueOf();
+}
+}
+
+if(changed){
+lastResult=parsedExpression(scope);
+}
+
+returnlastResult;
+},listener,objectEquality);
+}
+
 functiononeTimeWatchDelegate(scope,listener,objectEquality,parsedExpression){
 varunwatch,lastValue;
 returnunwatch=scope.$watch(functiononeTimeWatch(scope){
@@ -1122,7 +1213,18 @@ function $ParseProvider() {
 // initial value is defined (for bind-once)
 returnisDefined(value) ? result : value;
 };
-fn.$$watchDelegate=parsedExpression.$$watchDelegate;
+
+// Propagate $$watchDelegates other then inputsWatchDelegate
+if(parsedExpression.$$watchDelegate&&
+parsedExpression.$$watchDelegate!==inputsWatchDelegate){
+fn.$$watchDelegate=parsedExpression.$$watchDelegate;
+}elseif(!interceptorFn.$stateful){
+// If there is an interceptor, but no watchDelegate then treat the interceptor like
+// we treat filters - it is assumed to be a pure function unless flagged with $stateful
+fn.$$watchDelegate=inputsWatchDelegate;
+fn.inputs=[parsedExpression];
+}
+
 returnfn;
 }
 }];

src/ng/rootScope.js

@@ -515,6 +515,8 @@ function $RootScopeProvider(){
  * de-registration function is executed, the internal watch operation is terminated.
  */
 $watchCollection: function(obj,listener){
+$watchCollectionInterceptor.$stateful=true;
+
 varself=this;
 // the current value, updated on each dirty-check run
 varnewValue;

test/ng/directive/ngRepeatSpec.js

@@ -867,12 +867,15 @@ describe('ngRepeat', function() {
 // This creates one item, but it has no parent so we can't get to it
 $rootScope.items=[1,2];
 $rootScope.$apply();
+expect(logs).toContain(1);
+expect(logs).toContain(2);
+logs.length=0;
 
 // This cleans up to prevent memory leak
 $rootScope.items=[];
 $rootScope.$apply();
 expect(angular.mock.dump(element)).toBe('<!-- ngRepeat: i in items -->');
-expect(logs).toEqual([1,2,1,2]);
+expect(logs.length).toBe(0);
 }));
 
 
@@ -894,12 +897,15 @@ describe('ngRepeat', function() {
 // This creates one item, but it has no parent so we can't get to it
 $rootScope.items=[1,2];
 $rootScope.$apply();
+expect(logs).toContain(1);
+expect(logs).toContain(2);
+logs.length=0;
 
 // This cleans up to prevent memory leak
 $rootScope.items=[];
 $rootScope.$apply();
 expect(sortedHtml(element)).toBe('<span>-</span><!-- ngRepeat: i in items --><span>-</span>');
-expect(logs).toEqual([1,2,1,2]);
+expect(logs.length).toBe(0);
 }));
 
 

benchmarks/parsed-expressions-bp/main.html

@@ -31,6 +31,11 @@
 <labelfor="operators">Binary/Unary operators</label>
 </li>
 
+<li>
+<inputtype="radio" ng-model="expressionType" value="shortCircuitingOperators" id="shortCircuitingOperators">
+<labelfor="shortCircuitingOperators">AND/OR short-circuiting operators</label>
+</li>
+
 <li>
 <inputtype="radio" ng-model="expressionType" value="filters" id="filters">
 <labelfor="filters">Filters</label>
@@ -134,6 +139,17 @@
 <spanbm-pe-watch="-rowIdx * 2 * rowIdx + rowIdx / rowIdx + 1"></span>
 </li>
 
+<ling-switch-when="shortCircuitingOperators" ng-repeat="(rowIdx, row) in ::data">
+<spanbm-pe-watch="rowIdx && row.odd"></span>
+<spanbm-pe-watch="row.odd && row.even"></span>
+<spanbm-pe-watch="row.odd && !row.even"></span>
+<spanbm-pe-watch="row.odd || row.even"></span>
+<spanbm-pe-watch="row.odd || row.even || row.index"></span>
+<spanbm-pe-watch="row.index === 1 || row.index === 2"></span>
+<spanbm-pe-watch="row.num0 < row.num1 && row.num1 < row.num2"></span>
+<spanbm-pe-watch="row.num0 < row.num1 || row.num1 < row.num2"></span>
+</li>
+
 <ling-switch-when="filters" ng-repeat="(rowIdx, row) in ::data">
 <spanbm-pe-watch="rowIdx | noop"></span>
 <spanbm-pe-watch="rowIdx | noop"></span>

src/ng/compile.js

@@ -1725,7 +1725,7 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
 attrs[attrName],newIsolateScopeDirective.name);
 };
 lastValue=isolateBindingContext[scopeName]=parentGet(scope);
-varunwatch=scope.$watch($parse(attrs[attrName],functionparentValueWatch(parentValue){
+varparentValueWatch=functionparentValueWatch(parentValue){
 if(!compare(parentValue,isolateBindingContext[scopeName])){
 // we are out of sync and need to copy
 if(!compare(parentValue,lastValue)){
@@ -1737,7 +1737,9 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
 }
 }
 returnlastValue=parentValue;
-}),null,parentGet.literal);
+};
+parentValueWatch.$stateful=true;
+varunwatch=scope.$watch($parse(attrs[attrName],parentValueWatch),null,parentGet.literal);
 isolateScope.$on('$destroy',unwatch);
 break;
 

src/ng/parse.js

@@ -376,6 +376,10 @@ Lexer.prototype = {
 };
 
 
+functionisConstant(exp){
+returnexp.constant;
+}
+
 /**
  * @constructor
  */
@@ -493,7 +497,8 @@ Parser.prototype = {
 returnextend(function(self,locals){
 returnfn(self,locals,right);
 },{
-constant:right.constant
+constant:right.constant,
+inputs: [right]
 });
 },
 
@@ -505,11 +510,12 @@ Parser.prototype = {
 });
 },
 
-binaryFn: function(left,fn,right){
+binaryFn: function(left,fn,right,isBranching){
 returnextend(function(self,locals){
 returnfn(self,locals,left,right);
 },{
-constant:left.constant&&right.constant
+constant: left.constant&&right.constant,
+inputs: !isBranching&&[left,right]
 });
 },
 
@@ -557,7 +563,9 @@ Parser.prototype = {
 }
 }
 
-returnfunction$parseFilter(self,locals){
+varinputs=[inputFn].concat(argsFn||[]);
+
+returnextend(function$parseFilter(self,locals){
 varinput=inputFn(self,locals);
 if(args){
 args[0]=input;
@@ -571,7 +579,10 @@ Parser.prototype = {
 }
 
 returnfn(input);
-};
+},{
+constant: !fn.$stateful&&inputs.every(isConstant),
+inputs: !fn.$stateful&&inputs
+});
 },
 
 expression: function(){
@@ -588,9 +599,11 @@ Parser.prototype = {
 this.text.substring(0,token.index)+'] can not be assigned to',token);
 }
 right=this.ternary();
-returnfunction$parseAssignment(scope,locals){
+returnextend(function$parseAssignment(scope,locals){
 returnleft.assign(scope,right(scope,locals),locals);
-};
+},{
+inputs: [left,right]
+});
 }
 returnleft;
 },
@@ -615,7 +628,7 @@ Parser.prototype = {
 varleft=this.logicalAND();
 vartoken;
 while((token=this.expect('||'))){
-left=this.binaryFn(left,token.fn,this.logicalAND());
+left=this.binaryFn(left,token.fn,this.logicalAND(),true);
 }
 returnleft;
 },
@@ -624,7 +637,7 @@ Parser.prototype = {
 varleft=this.equality();
 vartoken;
 if((token=this.expect('&&'))){
-left=this.binaryFn(left,token.fn,this.logicalAND());
+left=this.binaryFn(left,token.fn,this.logicalAND(),true);
 }
 returnleft;
 },
@@ -759,7 +772,6 @@ Parser.prototype = {
 // This is used with json array declaration
 arrayDeclaration: function(){
 varelementFns=[];
-varallConstant=true;
 if(this.peekToken().text!==']'){
 do{
 if(this.peek(']')){
@@ -768,9 +780,6 @@ Parser.prototype = {
 }
 varelementFn=this.expression();
 elementFns.push(elementFn);
-if(!elementFn.constant){
-allConstant=false;
-}
 }while(this.expect(','));
 }
 this.consume(']');
@@ -783,13 +792,13 @@ Parser.prototype = {
 returnarray;
 },{
 literal: true,
-constant: allConstant
+constant: elementFns.every(isConstant),
+inputs: elementFns
 });
 },
 
 object: function(){
 varkeys=[],valueFns=[];
-varallConstant=true;
 if(this.peekToken().text!=='}'){
 do{
 if(this.peek('}')){
@@ -801,9 +810,6 @@ Parser.prototype = {
 this.consume(':');
 varvalue=this.expression();
 valueFns.push(value);
-if(!value.constant){
-allConstant=false;
-}
 }while(this.expect(','));
 }
 this.consume('}');
@@ -816,7 +822,8 @@ Parser.prototype = {
 returnobject;
 },{
 literal: true,
-constant: allConstant
+constant: valueFns.every(isConstant),
+inputs: valueFns
 });
 }
 };
@@ -1043,6 +1050,8 @@ function $ParseProvider() {
 parsedExpression=wrapSharedExpression(parsedExpression);
 parsedExpression.$$watchDelegate=parsedExpression.literal ?
 oneTimeLiteralWatchDelegate : oneTimeWatchDelegate;
+}elseif(parsedExpression.inputs){
+parsedExpression.$$watchDelegate=inputsWatchDelegate;
 }
 
 cache[cacheKey]=parsedExpression;
@@ -1057,6 +1066,88 @@ function $ParseProvider() {
 }
 };
 
+functioncollectExpressionInputs(inputs,list){
+for(vari=0,ii=inputs.length;i<ii;i++){
+varinput=inputs[i];
+if(!input.constant){
+if(input.inputs){
+collectExpressionInputs(input.inputs,list);
+}elseif(list.indexOf(input)===-1){// TODO(perf) can we do better?
+list.push(input);
+}
+}
+}
+
+returnlist;
+}
+
+functionexpressionInputDirtyCheck(newValue,oldValueOfValue){
+
+if(newValue==null||oldValueOfValue==null){// null/undefined
+returnnewValue===oldValueOfValue;
+}
+
+if(typeofnewValue==='object'){
+
+// attempt to convert the value to a primitive type
+// TODO(docs): add a note to docs that by implementing valueOf even objects and arrays can
+// be cheaply dirty-checked
+newValue=newValue.valueOf();
+
+if(typeofnewValue==='object'){
+// objects/arrays are not supported - deep-watching them would be too expensive
+returnfalse;
+}
+
+// fall-through to the primitive equality check
+}
+
+//Primitive or NaN
+returnnewValue===oldValueOfValue||(newValue!==newValue&&oldValueOfValue!==oldValueOfValue);
+}
+
+functioninputsWatchDelegate(scope,listener,objectEquality,parsedExpression){
+varinputExpressions=parsedExpression.$$inputs||
+(parsedExpression.$$inputs=collectExpressionInputs(parsedExpression.inputs,[]));
+
+varlastResult;
+
+if(inputExpressions.length===1){
+varoldInputValue=expressionInputDirtyCheck;// init to something unique so that equals check fails
+inputExpressions=inputExpressions[0];
+returnscope.$watch(functionexpressionInputWatch(scope){
+varnewInputValue=inputExpressions(scope);
+if(!expressionInputDirtyCheck(newInputValue,oldInputValue)){
+lastResult=parsedExpression(scope);
+oldInputValue=newInputValue&&newInputValue.valueOf();
+}
+returnlastResult;
+},listener,objectEquality);
+}
+
+varoldInputValueOfValues=[];
+for(vari=0,ii=inputExpressions.length;i<ii;i++){
+oldInputValueOfValues[i]=expressionInputDirtyCheck;// init to something unique so that equals check fails
+}
+
+returnscope.$watch(functionexpressionInputsWatch(scope){
+varchanged=false;
+
+for(vari=0,ii=inputExpressions.length;i<ii;i++){
+varnewInputValue=inputExpressions[i](scope);
+if(changed||(changed=!expressionInputDirtyCheck(newInputValue,oldInputValueOfValues[i]))){
+oldInputValueOfValues[i]=newInputValue&&newInputValue.valueOf();
+}
+}
+
+if(changed){
+lastResult=parsedExpression(scope);
+}
+
+returnlastResult;
+},listener,objectEquality);
+}
+
 functiononeTimeWatchDelegate(scope,listener,objectEquality,parsedExpression){
 varunwatch,lastValue;
 returnunwatch=scope.$watch(functiononeTimeWatch(scope){
@@ -1122,7 +1213,18 @@ function $ParseProvider() {
 // initial value is defined (for bind-once)
 returnisDefined(value) ? result : value;
 };
-fn.$$watchDelegate=parsedExpression.$$watchDelegate;
+
+// Propagate $$watchDelegates other then inputsWatchDelegate
+if(parsedExpression.$$watchDelegate&&
+parsedExpression.$$watchDelegate!==inputsWatchDelegate){
+fn.$$watchDelegate=parsedExpression.$$watchDelegate;
+}elseif(!interceptorFn.$stateful){
+// If there is an interceptor, but no watchDelegate then treat the interceptor like
+// we treat filters - it is assumed to be a pure function unless flagged with $stateful
+fn.$$watchDelegate=inputsWatchDelegate;
+fn.inputs=[parsedExpression];
+}
+
 returnfn;
 }
 }];

src/ng/rootScope.js

@@ -515,6 +515,8 @@ function $RootScopeProvider(){
  * de-registration function is executed, the internal watch operation is terminated.
  */
 $watchCollection: function(obj,listener){
+$watchCollectionInterceptor.$stateful=true;
+
 varself=this;
 // the current value, updated on each dirty-check run
 varnewValue;

test/ng/directive/ngRepeatSpec.js

@@ -867,12 +867,15 @@ describe('ngRepeat', function() {
 // This creates one item, but it has no parent so we can't get to it
 $rootScope.items=[1,2];
 $rootScope.$apply();
+expect(logs).toContain(1);
+expect(logs).toContain(2);
+logs.length=0;
 
 // This cleans up to prevent memory leak
 $rootScope.items=[];
 $rootScope.$apply();
 expect(angular.mock.dump(element)).toBe('<!-- ngRepeat: i in items -->');
-expect(logs).toEqual([1,2,1,2]);
+expect(logs.length).toBe(0);
 }));
 
 
@@ -894,12 +897,15 @@ describe('ngRepeat', function() {
 // This creates one item, but it has no parent so we can't get to it
 $rootScope.items=[1,2];
 $rootScope.$apply();
+expect(logs).toContain(1);
+expect(logs).toContain(2);
+logs.length=0;
 
 // This cleans up to prevent memory leak
 $rootScope.items=[];
 $rootScope.$apply();
 expect(sortedHtml(element)).toBe('<span>-</span><!-- ngRepeat: i in items --><span>-</span>');
-expect(logs).toEqual([1,2,1,2]);
+expect(logs.length).toBe(0);
 }));
 
 

benchmarks/parsed-expressions-bp/main.html

@@ -31,6 +31,11 @@
 <labelfor="operators">Binary/Unary operators</label>
 </li>
 
+<li>
+<inputtype="radio" ng-model="expressionType" value="shortCircuitingOperators" id="shortCircuitingOperators">
+<labelfor="shortCircuitingOperators">AND/OR short-circuiting operators</label>
+</li>
+
 <li>
 <inputtype="radio" ng-model="expressionType" value="filters" id="filters">
 <labelfor="filters">Filters</label>
@@ -134,6 +139,17 @@
 <spanbm-pe-watch="-rowIdx * 2 * rowIdx + rowIdx / rowIdx + 1"></span>
 </li>
 
+<ling-switch-when="shortCircuitingOperators" ng-repeat="(rowIdx, row) in ::data">
+<spanbm-pe-watch="rowIdx && row.odd"></span>
+<spanbm-pe-watch="row.odd && row.even"></span>
+<spanbm-pe-watch="row.odd && !row.even"></span>
+<spanbm-pe-watch="row.odd || row.even"></span>
+<spanbm-pe-watch="row.odd || row.even || row.index"></span>
+<spanbm-pe-watch="row.index === 1 || row.index === 2"></span>
+<spanbm-pe-watch="row.num0 < row.num1 && row.num1 < row.num2"></span>
+<spanbm-pe-watch="row.num0 < row.num1 || row.num1 < row.num2"></span>
+</li>
+
 <ling-switch-when="filters" ng-repeat="(rowIdx, row) in ::data">
 <spanbm-pe-watch="rowIdx | noop"></span>
 <spanbm-pe-watch="rowIdx | noop"></span>

src/ng/compile.js

@@ -1725,7 +1725,7 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
 attrs[attrName],newIsolateScopeDirective.name);
 };
 lastValue=isolateBindingContext[scopeName]=parentGet(scope);
-varunwatch=scope.$watch($parse(attrs[attrName],functionparentValueWatch(parentValue){
+varparentValueWatch=functionparentValueWatch(parentValue){
 if(!compare(parentValue,isolateBindingContext[scopeName])){
 // we are out of sync and need to copy
 if(!compare(parentValue,lastValue)){
@@ -1737,7 +1737,9 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
 }
 }
 returnlastValue=parentValue;
-}),null,parentGet.literal);
+};
+parentValueWatch.$stateful=true;
+varunwatch=scope.$watch($parse(attrs[attrName],parentValueWatch),null,parentGet.literal);
 isolateScope.$on('$destroy',unwatch);
 break;
 

src/ng/parse.js

@@ -376,6 +376,10 @@ Lexer.prototype = {
 };
 
 
+functionisConstant(exp){
+returnexp.constant;
+}
+
 /**
  * @constructor
  */
@@ -493,7 +497,8 @@ Parser.prototype = {
 returnextend(function(self,locals){
 returnfn(self,locals,right);
 },{
-constant:right.constant
+constant:right.constant,
+inputs: [right]
 });
 },
 
@@ -505,11 +510,12 @@ Parser.prototype = {
 });
 },
 
-binaryFn: function(left,fn,right){
+binaryFn: function(left,fn,right,isBranching){
 returnextend(function(self,locals){
 returnfn(self,locals,left,right);
 },{
-constant:left.constant&&right.constant
+constant: left.constant&&right.constant,
+inputs: !isBranching&&[left,right]
 });
 },
 
@@ -557,7 +563,9 @@ Parser.prototype = {
 }
 }
 
-returnfunction$parseFilter(self,locals){
+varinputs=[inputFn].concat(argsFn||[]);
+
+returnextend(function$parseFilter(self,locals){
 varinput=inputFn(self,locals);
 if(args){
 args[0]=input;
@@ -571,7 +579,10 @@ Parser.prototype = {
 }
 
 returnfn(input);
-};
+},{
+constant: !fn.$stateful&&inputs.every(isConstant),
+inputs: !fn.$stateful&&inputs
+});
 },
 
 expression: function(){
@@ -588,9 +599,11 @@ Parser.prototype = {
 this.text.substring(0,token.index)+'] can not be assigned to',token);
 }
 right=this.ternary();
-returnfunction$parseAssignment(scope,locals){
+returnextend(function$parseAssignment(scope,locals){
 returnleft.assign(scope,right(scope,locals),locals);
-};
+},{
+inputs: [left,right]
+});
 }
 returnleft;
 },
@@ -615,7 +628,7 @@ Parser.prototype = {
 varleft=this.logicalAND();
 vartoken;
 while((token=this.expect('||'))){
-left=this.binaryFn(left,token.fn,this.logicalAND());
+left=this.binaryFn(left,token.fn,this.logicalAND(),true);
 }
 returnleft;
 },
@@ -624,7 +637,7 @@ Parser.prototype = {
 varleft=this.equality();
 vartoken;
 if((token=this.expect('&&'))){
-left=this.binaryFn(left,token.fn,this.logicalAND());
+left=this.binaryFn(left,token.fn,this.logicalAND(),true);
 }
 returnleft;
 },
@@ -759,7 +772,6 @@ Parser.prototype = {
 // This is used with json array declaration
 arrayDeclaration: function(){
 varelementFns=[];
-varallConstant=true;
 if(this.peekToken().text!==']'){
 do{
 if(this.peek(']')){
@@ -768,9 +780,6 @@ Parser.prototype = {
 }
 varelementFn=this.expression();
 elementFns.push(elementFn);
-if(!elementFn.constant){
-allConstant=false;
-}
 }while(this.expect(','));
 }
 this.consume(']');
@@ -783,13 +792,13 @@ Parser.prototype = {
 returnarray;
 },{
 literal: true,
-constant: allConstant
+constant: elementFns.every(isConstant),
+inputs: elementFns
 });
 },
 
 object: function(){
 varkeys=[],valueFns=[];
-varallConstant=true;
 if(this.peekToken().text!=='}'){
 do{
 if(this.peek('}')){
@@ -801,9 +810,6 @@ Parser.prototype = {
 this.consume(':');
 varvalue=this.expression();
 valueFns.push(value);
-if(!value.constant){
-allConstant=false;
-}
 }while(this.expect(','));
 }
 this.consume('}');
@@ -816,7 +822,8 @@ Parser.prototype = {
 returnobject;
 },{
 literal: true,
-constant: allConstant
+constant: valueFns.every(isConstant),
+inputs: valueFns
 });
 }
 };
@@ -1043,6 +1050,8 @@ function $ParseProvider() {
 parsedExpression=wrapSharedExpression(parsedExpression);
 parsedExpression.$$watchDelegate=parsedExpression.literal ?
 oneTimeLiteralWatchDelegate : oneTimeWatchDelegate;
+}elseif(parsedExpression.inputs){
+parsedExpression.$$watchDelegate=inputsWatchDelegate;
 }
 
 cache[cacheKey]=parsedExpression;
@@ -1057,6 +1066,88 @@ function $ParseProvider() {
 }
 };
 
+functioncollectExpressionInputs(inputs,list){
+for(vari=0,ii=inputs.length;i<ii;i++){
+varinput=inputs[i];
+if(!input.constant){
+if(input.inputs){
+collectExpressionInputs(input.inputs,list);
+}elseif(list.indexOf(input)===-1){// TODO(perf) can we do better?
+list.push(input);
+}
+}
+}
+
+returnlist;
+}
+
+functionexpressionInputDirtyCheck(newValue,oldValueOfValue){
+
+if(newValue==null||oldValueOfValue==null){// null/undefined
+returnnewValue===oldValueOfValue;
+}
+
+if(typeofnewValue==='object'){
+
+// attempt to convert the value to a primitive type
+// TODO(docs): add a note to docs that by implementing valueOf even objects and arrays can
+// be cheaply dirty-checked
+newValue=newValue.valueOf();
+
+if(typeofnewValue==='object'){
+// objects/arrays are not supported - deep-watching them would be too expensive
+returnfalse;
+}
+
+// fall-through to the primitive equality check
+}
+
+//Primitive or NaN
+returnnewValue===oldValueOfValue||(newValue!==newValue&&oldValueOfValue!==oldValueOfValue);
+}
+
+functioninputsWatchDelegate(scope,listener,objectEquality,parsedExpression){
+varinputExpressions=parsedExpression.$$inputs||
+(parsedExpression.$$inputs=collectExpressionInputs(parsedExpression.inputs,[]));
+
+varlastResult;
+
+if(inputExpressions.length===1){
+varoldInputValue=expressionInputDirtyCheck;// init to something unique so that equals check fails
+inputExpressions=inputExpressions[0];
+returnscope.$watch(functionexpressionInputWatch(scope){
+varnewInputValue=inputExpressions(scope);
+if(!expressionInputDirtyCheck(newInputValue,oldInputValue)){
+lastResult=parsedExpression(scope);
+oldInputValue=newInputValue&&newInputValue.valueOf();
+}
+returnlastResult;
+},listener,objectEquality);
+}
+
+varoldInputValueOfValues=[];
+for(vari=0,ii=inputExpressions.length;i<ii;i++){
+oldInputValueOfValues[i]=expressionInputDirtyCheck;// init to something unique so that equals check fails
+}
+
+returnscope.$watch(functionexpressionInputsWatch(scope){
+varchanged=false;
+
+for(vari=0,ii=inputExpressions.length;i<ii;i++){
+varnewInputValue=inputExpressions[i](scope);
+if(changed||(changed=!expressionInputDirtyCheck(newInputValue,oldInputValueOfValues[i]))){
+oldInputValueOfValues[i]=newInputValue&&newInputValue.valueOf();
+}
+}
+
+if(changed){
+lastResult=parsedExpression(scope);
+}
+
+returnlastResult;
+},listener,objectEquality);
+}
+
 functiononeTimeWatchDelegate(scope,listener,objectEquality,parsedExpression){
 varunwatch,lastValue;
 returnunwatch=scope.$watch(functiononeTimeWatch(scope){
@@ -1122,7 +1213,18 @@ function $ParseProvider() {
 // initial value is defined (for bind-once)
 returnisDefined(value) ? result : value;
 };
-fn.$$watchDelegate=parsedExpression.$$watchDelegate;
+
+// Propagate $$watchDelegates other then inputsWatchDelegate
+if(parsedExpression.$$watchDelegate&&
+parsedExpression.$$watchDelegate!==inputsWatchDelegate){
+fn.$$watchDelegate=parsedExpression.$$watchDelegate;
+}elseif(!interceptorFn.$stateful){
+// If there is an interceptor, but no watchDelegate then treat the interceptor like
+// we treat filters - it is assumed to be a pure function unless flagged with $stateful
+fn.$$watchDelegate=inputsWatchDelegate;
+fn.inputs=[parsedExpression];
+}
+
 returnfn;
 }
 }];

src/ng/rootScope.js

@@ -515,6 +515,8 @@ function $RootScopeProvider(){
  * de-registration function is executed, the internal watch operation is terminated.
  */
 $watchCollection: function(obj,listener){
+$watchCollectionInterceptor.$stateful=true;
+
 varself=this;
 // the current value, updated on each dirty-check run
 varnewValue;

test/ng/directive/ngRepeatSpec.js

@@ -867,12 +867,15 @@ describe('ngRepeat', function() {
 // This creates one item, but it has no parent so we can't get to it
 $rootScope.items=[1,2];
 $rootScope.$apply();
+expect(logs).toContain(1);
+expect(logs).toContain(2);
+logs.length=0;
 
 // This cleans up to prevent memory leak
 $rootScope.items=[];
 $rootScope.$apply();
 expect(angular.mock.dump(element)).toBe('<!-- ngRepeat: i in items -->');
-expect(logs).toEqual([1,2,1,2]);
+expect(logs.length).toBe(0);
 }));
 
 
@@ -894,12 +897,15 @@ describe('ngRepeat', function() {
 // This creates one item, but it has no parent so we can't get to it
 $rootScope.items=[1,2];
 $rootScope.$apply();
+expect(logs).toContain(1);
+expect(logs).toContain(2);
+logs.length=0;
 
 // This cleans up to prevent memory leak
 $rootScope.items=[];
 $rootScope.$apply();
 expect(sortedHtml(element)).toBe('<span>-</span><!-- ngRepeat: i in items --><span>-</span>');
-expect(logs).toEqual([1,2,1,2]);
+expect(logs.length).toBe(0);
 }));
 
 

benchmarks/parsed-expressions-bp/main.html

@@ -31,6 +31,11 @@
 <labelfor="operators">Binary/Unary operators</label>
 </li>
 
+<li>
+<inputtype="radio" ng-model="expressionType" value="shortCircuitingOperators" id="shortCircuitingOperators">
+<labelfor="shortCircuitingOperators">AND/OR short-circuiting operators</label>
+</li>
+
 <li>
 <inputtype="radio" ng-model="expressionType" value="filters" id="filters">
 <labelfor="filters">Filters</label>
@@ -134,6 +139,17 @@
 <spanbm-pe-watch="-rowIdx * 2 * rowIdx + rowIdx / rowIdx + 1"></span>
 </li>
 
+<ling-switch-when="shortCircuitingOperators" ng-repeat="(rowIdx, row) in ::data">
+<spanbm-pe-watch="rowIdx && row.odd"></span>
+<spanbm-pe-watch="row.odd && row.even"></span>
+<spanbm-pe-watch="row.odd && !row.even"></span>
+<spanbm-pe-watch="row.odd || row.even"></span>
+<spanbm-pe-watch="row.odd || row.even || row.index"></span>
+<spanbm-pe-watch="row.index === 1 || row.index === 2"></span>
+<spanbm-pe-watch="row.num0 < row.num1 && row.num1 < row.num2"></span>
+<spanbm-pe-watch="row.num0 < row.num1 || row.num1 < row.num2"></span>
+</li>
+
 <ling-switch-when="filters" ng-repeat="(rowIdx, row) in ::data">
 <spanbm-pe-watch="rowIdx | noop"></span>
 <spanbm-pe-watch="rowIdx | noop"></span>

src/ng/compile.js

@@ -1725,7 +1725,7 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
 attrs[attrName],newIsolateScopeDirective.name);
 };
 lastValue=isolateBindingContext[scopeName]=parentGet(scope);
-varunwatch=scope.$watch($parse(attrs[attrName],functionparentValueWatch(parentValue){
+varparentValueWatch=functionparentValueWatch(parentValue){
 if(!compare(parentValue,isolateBindingContext[scopeName])){
 // we are out of sync and need to copy
 if(!compare(parentValue,lastValue)){
@@ -1737,7 +1737,9 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
 }
 }
 returnlastValue=parentValue;
-}),null,parentGet.literal);
+};
+parentValueWatch.$stateful=true;
+varunwatch=scope.$watch($parse(attrs[attrName],parentValueWatch),null,parentGet.literal);
 isolateScope.$on('$destroy',unwatch);
 break;
 

src/ng/parse.js

@@ -376,6 +376,10 @@ Lexer.prototype = {
 };
 
 
+functionisConstant(exp){
+returnexp.constant;
+}
+
 /**
  * @constructor
  */
@@ -493,7 +497,8 @@ Parser.prototype = {
 returnextend(function(self,locals){
 returnfn(self,locals,right);
 },{
-constant:right.constant
+constant:right.constant,
+inputs: [right]
 });
 },
 
@@ -505,11 +510,12 @@ Parser.prototype = {
 });
 },
 
-binaryFn: function(left,fn,right){
+binaryFn: function(left,fn,right,isBranching){
 returnextend(function(self,locals){
 returnfn(self,locals,left,right);
 },{
-constant:left.constant&&right.constant
+constant: left.constant&&right.constant,
+inputs: !isBranching&&[left,right]
 });
 },
 
@@ -557,7 +563,9 @@ Parser.prototype = {
 }
 }
 
-returnfunction$parseFilter(self,locals){
+varinputs=[inputFn].concat(argsFn||[]);
+
+returnextend(function$parseFilter(self,locals){
 varinput=inputFn(self,locals);
 if(args){
 args[0]=input;
@@ -571,7 +579,10 @@ Parser.prototype = {
 }
 
 returnfn(input);
-};
+},{
+constant: !fn.$stateful&&inputs.every(isConstant),
+inputs: !fn.$stateful&&inputs
+});
 },
 
 expression: function(){
@@ -588,9 +599,11 @@ Parser.prototype = {
 this.text.substring(0,token.index)+'] can not be assigned to',token);
 }
 right=this.ternary();
-returnfunction$parseAssignment(scope,locals){
+returnextend(function$parseAssignment(scope,locals){
 returnleft.assign(scope,right(scope,locals),locals);
-};
+},{
+inputs: [left,right]
+});
 }
 returnleft;
 },
@@ -615,7 +628,7 @@ Parser.prototype = {
 varleft=this.logicalAND();
 vartoken;
 while((token=this.expect('||'))){
-left=this.binaryFn(left,token.fn,this.logicalAND());
+left=this.binaryFn(left,token.fn,this.logicalAND(),true);
 }
 returnleft;
 },
@@ -624,7 +637,7 @@ Parser.prototype = {
 varleft=this.equality();
 vartoken;
 if((token=this.expect('&&'))){
-left=this.binaryFn(left,token.fn,this.logicalAND());
+left=this.binaryFn(left,token.fn,this.logicalAND(),true);
 }
 returnleft;
 },
@@ -759,7 +772,6 @@ Parser.prototype = {
 // This is used with json array declaration
 arrayDeclaration: function(){
 varelementFns=[];
-varallConstant=true;
 if(this.peekToken().text!==']'){
 do{
 if(this.peek(']')){
@@ -768,9 +780,6 @@ Parser.prototype = {
 }
 varelementFn=this.expression();
 elementFns.push(elementFn);
-if(!elementFn.constant){
-allConstant=false;
-}
 }while(this.expect(','));
 }
 this.consume(']');
@@ -783,13 +792,13 @@ Parser.prototype = {
 returnarray;
 },{
 literal: true,
-constant: allConstant
+constant: elementFns.every(isConstant),
+inputs: elementFns
 });
 },
 
 object: function(){
 varkeys=[],valueFns=[];
-varallConstant=true;
 if(this.peekToken().text!=='}'){
 do{
 if(this.peek('}')){
@@ -801,9 +810,6 @@ Parser.prototype = {
 this.consume(':');
 varvalue=this.expression();
 valueFns.push(value);
-if(!value.constant){
-allConstant=false;
-}
 }while(this.expect(','));
 }
 this.consume('}');
@@ -816,7 +822,8 @@ Parser.prototype = {
 returnobject;
 },{
 literal: true,
-constant: allConstant
+constant: valueFns.every(isConstant),
+inputs: valueFns
 });
 }
 };
@@ -1043,6 +1050,8 @@ function $ParseProvider() {
 parsedExpression=wrapSharedExpression(parsedExpression);
 parsedExpression.$$watchDelegate=parsedExpression.literal ?
 oneTimeLiteralWatchDelegate : oneTimeWatchDelegate;
+}elseif(parsedExpression.inputs){
+parsedExpression.$$watchDelegate=inputsWatchDelegate;
 }
 
 cache[cacheKey]=parsedExpression;
@@ -1057,6 +1066,88 @@ function $ParseProvider() {
 }
 };
 
+functioncollectExpressionInputs(inputs,list){
+for(vari=0,ii=inputs.length;i<ii;i++){
+varinput=inputs[i];
+if(!input.constant){
+if(input.inputs){
+collectExpressionInputs(input.inputs,list);
+}elseif(list.indexOf(input)===-1){// TODO(perf) can we do better?
+list.push(input);
+}
+}
+}
+
+returnlist;
+}
+
+functionexpressionInputDirtyCheck(newValue,oldValueOfValue){
+
+if(newValue==null||oldValueOfValue==null){// null/undefined
+returnnewValue===oldValueOfValue;
+}
+
+if(typeofnewValue==='object'){
+
+// attempt to convert the value to a primitive type
+// TODO(docs): add a note to docs that by implementing valueOf even objects and arrays can
+// be cheaply dirty-checked
+newValue=newValue.valueOf();
+
+if(typeofnewValue==='object'){
+// objects/arrays are not supported - deep-watching them would be too expensive
+returnfalse;
+}
+
+// fall-through to the primitive equality check
+}
+
+//Primitive or NaN
+returnnewValue===oldValueOfValue||(newValue!==newValue&&oldValueOfValue!==oldValueOfValue);
+}
+
+functioninputsWatchDelegate(scope,listener,objectEquality,parsedExpression){
+varinputExpressions=parsedExpression.$$inputs||
+(parsedExpression.$$inputs=collectExpressionInputs(parsedExpression.inputs,[]));
+
+varlastResult;
+
+if(inputExpressions.length===1){
+varoldInputValue=expressionInputDirtyCheck;// init to something unique so that equals check fails
+inputExpressions=inputExpressions[0];
+returnscope.$watch(functionexpressionInputWatch(scope){
+varnewInputValue=inputExpressions(scope);
+if(!expressionInputDirtyCheck(newInputValue,oldInputValue)){
+lastResult=parsedExpression(scope);
+oldInputValue=newInputValue&&newInputValue.valueOf();
+}
+returnlastResult;
+},listener,objectEquality);
+}
+
+varoldInputValueOfValues=[];
+for(vari=0,ii=inputExpressions.length;i<ii;i++){
+oldInputValueOfValues[i]=expressionInputDirtyCheck;// init to something unique so that equals check fails
+}
+
+returnscope.$watch(functionexpressionInputsWatch(scope){
+varchanged=false;
+
+for(vari=0,ii=inputExpressions.length;i<ii;i++){
+varnewInputValue=inputExpressions[i](scope);
+if(changed||(changed=!expressionInputDirtyCheck(newInputValue,oldInputValueOfValues[i]))){
+oldInputValueOfValues[i]=newInputValue&&newInputValue.valueOf();
+}
+}
+
+if(changed){
+lastResult=parsedExpression(scope);
+}
+
+returnlastResult;
+},listener,objectEquality);
+}
+
 functiononeTimeWatchDelegate(scope,listener,objectEquality,parsedExpression){
 varunwatch,lastValue;
 returnunwatch=scope.$watch(functiononeTimeWatch(scope){
@@ -1122,7 +1213,18 @@ function $ParseProvider() {
 // initial value is defined (for bind-once)
 returnisDefined(value) ? result : value;
 };
-fn.$$watchDelegate=parsedExpression.$$watchDelegate;
+
+// Propagate $$watchDelegates other then inputsWatchDelegate
+if(parsedExpression.$$watchDelegate&&
+parsedExpression.$$watchDelegate!==inputsWatchDelegate){
+fn.$$watchDelegate=parsedExpression.$$watchDelegate;
+}elseif(!interceptorFn.$stateful){
+// If there is an interceptor, but no watchDelegate then treat the interceptor like
+// we treat filters - it is assumed to be a pure function unless flagged with $stateful
+fn.$$watchDelegate=inputsWatchDelegate;
+fn.inputs=[parsedExpression];
+}
+
 returnfn;
 }
 }];

src/ng/rootScope.js

@@ -515,6 +515,8 @@ function $RootScopeProvider(){
  * de-registration function is executed, the internal watch operation is terminated.
  */
 $watchCollection: function(obj,listener){
+$watchCollectionInterceptor.$stateful=true;
+
 varself=this;
 // the current value, updated on each dirty-check run
 varnewValue;

test/ng/directive/ngRepeatSpec.js

@@ -867,12 +867,15 @@ describe('ngRepeat', function() {
 // This creates one item, but it has no parent so we can't get to it
 $rootScope.items=[1,2];
 $rootScope.$apply();
+expect(logs).toContain(1);
+expect(logs).toContain(2);
+logs.length=0;
 
 // This cleans up to prevent memory leak
 $rootScope.items=[];
 $rootScope.$apply();
 expect(angular.mock.dump(element)).toBe('<!-- ngRepeat: i in items -->');
-expect(logs).toEqual([1,2,1,2]);
+expect(logs.length).toBe(0);
 }));
 
 
@@ -894,12 +897,15 @@ describe('ngRepeat', function() {
 // This creates one item, but it has no parent so we can't get to it
 $rootScope.items=[1,2];
 $rootScope.$apply();
+expect(logs).toContain(1);
+expect(logs).toContain(2);
+logs.length=0;
 
 // This cleans up to prevent memory leak
 $rootScope.items=[];
 $rootScope.$apply();
 expect(sortedHtml(element)).toBe('<span>-</span><!-- ngRepeat: i in items --><span>-</span>');
-expect(logs).toEqual([1,2,1,2]);
+expect(logs.length).toBe(0);
 }));