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fix($rootScope): fix potential memory leak when removing scope listeners
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Previously the array entry for listeners was set to null but the array size was not
trimmed until the event was broadcasted again (see angular@e6966e0).

By keeping track of the listener iteration index globally it can be adjusted if a listener
removal effects the index.

Fixes angular#16135

BREAKING CHANGE:

`$emit`/`$broadcast` listeners of a specific event name on a scope can no
longer be recursivly invoked.
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@jbedard
jbedard committed Oct 21, 2017
1 parent e04b833 commit 09e46b2
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Showing 2 changed files with 82 additions and 55 deletions.
85 changes: 32 additions & 53 deletions src/ng/rootScope.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1167,7 +1167,7 @@ function $RootScopeProvider() {
$on: function(name, listener) {
var namedListeners = this.$$listeners[name];
if (!namedListeners) {
this.$$listeners[name] = namedListeners = [];
this.$$listeners[name] = namedListeners = extend([], {$$index: -1});
}
namedListeners.push(listener);

Expand All @@ -1181,10 +1181,12 @@ function $RootScopeProvider() {

var self = this;
return function() {
var indexOfListener = namedListeners.indexOf(listener);
if (indexOfListener !== -1) {
namedListeners[indexOfListener] = null;
var index = arrayRemove(namedListeners, listener);
if (index >= 0) {
decrementListenerCount(self, 1, name);
if (index <= namedListeners.$$index) {
namedListeners.$$index--;
}
}
};
},
Expand Down Expand Up @@ -1213,9 +1215,7 @@ function $RootScopeProvider() {
* @return {Object} Event object (see {@link ng.$rootScope.Scope#$on}).
*/
$emit: function(name, args) {
var empty = [],
namedListeners,
scope = this,
var scope = this,
stopPropagation = false,
event = {
name: name,
Expand All @@ -1226,36 +1226,14 @@ function $RootScopeProvider() {
},
defaultPrevented: false
},
listenerArgs = concat([event], arguments, 1),
i, length;
listenerArgs = concat([event], arguments, 1);

do {
namedListeners = scope.$$listeners[name] || empty;
event.currentScope = scope;
for (i = 0, length = namedListeners.length; i < length; i++) {

// if listeners were deregistered, defragment the array
if (!namedListeners[i]) {
namedListeners.splice(i, 1);
i--;
length--;
continue;
}
try {
//allow all listeners attached to the current scope to run
namedListeners[i].apply(null, listenerArgs);
} catch (e) {
$exceptionHandler(e);
}
}
//if any listener on the current scope stops propagation, prevent bubbling
if (stopPropagation) {
event.currentScope = null;
return event;
}
invokeListeners(scope, event, listenerArgs, name);

//traverse upwards
scope = scope.$parent;
} while (scope);
//if any listener on the current scope stops propagation, prevent bubbling
} while (!stopPropagation && (scope = scope.$parent));

event.currentScope = null;

Expand Down Expand Up @@ -1299,28 +1277,11 @@ function $RootScopeProvider() {

if (!target.$$listenerCount[name]) return event;

var listenerArgs = concat([event], arguments, 1),
listeners, i, length;
var listenerArgs = concat([event], arguments, 1);

//down while you can, then up and next sibling or up and next sibling until back at root
while ((current = next)) {
event.currentScope = current;
listeners = current.$$listeners[name] || [];
for (i = 0, length = listeners.length; i < length; i++) {
// if listeners were deregistered, defragment the array
if (!listeners[i]) {
listeners.splice(i, 1);
i--;
length--;
continue;
}

try {
listeners[i].apply(null, listenerArgs);
} catch (e) {
$exceptionHandler(e);
}
}
invokeListeners(current, event, listenerArgs, name);

// Insanity Warning: scope depth-first traversal
// yes, this code is a bit crazy, but it works and we have tests to prove it!
Expand Down Expand Up @@ -1350,6 +1311,24 @@ function $RootScopeProvider() {

return $rootScope;

function invokeListeners(scope, event, listenerArgs, name) {
var listeners = scope.$$listeners[name];
if (listeners) {
if (listeners.$$index !== -1) {
throw $rootScopeMinErr('inevt', '{0} already $emit/$broadcast-ing', name);
}
event.currentScope = scope;
for (listeners.$$index = 0; listeners.$$index < listeners.length; listeners.$$index++) {
try {
//allow all listeners attached to the current scope to run
listeners[listeners.$$index].apply(null, listenerArgs);
} catch (e) {
$exceptionHandler(e);
}
}
listeners.$$index = -1;
}
}

function beginPhase(phase) {
if ($rootScope.$$phase) {
Expand Down
52 changes: 50 additions & 2 deletions test/ng/rootScopeSpec.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2316,6 +2316,19 @@ describe('Scope', function() {
}));


// See issue https://github.com/angular/angular.js/issues/16135
it('should deallocate the listener array entry', inject(function($rootScope) {
var remove1 = $rootScope.$on('abc', noop);
$rootScope.$on('abc', noop);

expect($rootScope.$$listeners['abc'].length).toBe(2);

remove1();

expect($rootScope.$$listeners['abc'].length).toBe(1);
}));


it('should call next listener when removing current', inject(function($rootScope) {
var listener1 = jasmine.createSpy().and.callFake(function() { remove1(); });
var remove1 = $rootScope.$on('abc', listener1);
Expand Down Expand Up @@ -2442,6 +2455,41 @@ describe('Scope', function() {
expect($rootScope.$$listenerCount).toEqual({abc: 1});
expect(child.$$listenerCount).toEqual({abc: 1});
}));


it('should throw on recursive $broadcast', inject(function($rootScope) {
$rootScope.$on('e', function() { $rootScope.$broadcast('e'); });

expect(function() { $rootScope.$emit('e', 5); }).toThrowMinErr('$rootScope', 'inevt', 'e already $emit/$broadcast-ing');
expect(function() { $rootScope.$broadcast('e', 5); }).toThrowMinErr('$rootScope', 'inevt', 'e already $emit/$broadcast-ing');
}));


it('should throw on recursive $emit', inject(function($rootScope) {
$rootScope.$on('e', function() { $rootScope.$emit('e'); });

expect(function() { $rootScope.$emit('e', 5); }).toThrowMinErr('$rootScope', 'inevt', 'e already $emit/$broadcast-ing');
expect(function() { $rootScope.$broadcast('e', 5); }).toThrowMinErr('$rootScope', 'inevt', 'e already $emit/$broadcast-ing');
}));


it('should throw on recursive $broadcast on child listener', inject(function($rootScope) {
var child = $rootScope.$new();
child.$on('e', function() { $rootScope.$broadcast('e'); });

expect(function() { child.$emit('e', 5); }).toThrowMinErr('$rootScope', 'inevt', 'e already $emit/$broadcast-ing');
expect(function() { child.$broadcast('e', 5); }).toThrowMinErr('$rootScope', 'inevt', 'e already $emit/$broadcast-ing');
}));


it('should throw on recursive $emit parent listener', inject(function($rootScope) {
var child = $rootScope.$new();
$rootScope.$on('e', function() { child.$emit('e'); });

expect(function() { child.$emit('e', 5); }).toThrowMinErr('$rootScope', 'inevt', 'e already $emit/$broadcast-ing');
expect(function() { $rootScope.$emit('e', 5); }).toThrowMinErr('$rootScope', 'inevt', 'e already $emit/$broadcast-ing');
expect(function() { $rootScope.$broadcast('e', 5); }).toThrowMinErr('$rootScope', 'inevt', 'e already $emit/$broadcast-ing');
}));
});
});

Expand Down Expand Up @@ -2531,7 +2579,7 @@ describe('Scope', function() {
expect(spy1).toHaveBeenCalledOnce();
expect(spy2).toHaveBeenCalledOnce();
expect(spy3).toHaveBeenCalledOnce();
expect(child.$$listeners['evt'].length).toBe(3); // cleanup will happen on next $emit
expect(child.$$listeners['evt'].length).toBe(2);

spy1.calls.reset();
spy2.calls.reset();
Expand Down Expand Up @@ -2565,7 +2613,7 @@ describe('Scope', function() {
expect(spy1).toHaveBeenCalledOnce();
expect(spy2).toHaveBeenCalledOnce();
expect(spy3).toHaveBeenCalledOnce();
expect(child.$$listeners['evt'].length).toBe(3); //cleanup will happen on next $broadcast
expect(child.$$listeners['evt'].length).toBe(2);

spy1.calls.reset();
spy2.calls.reset();
Expand Down

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