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Calling EventTarget.removeEventListener twice causes errors #283
Description
Consider the following code snippet:
var elem = document.body;
var listener = function (event) {};
elem.addEventListener('click', listener, false);
elem.removeEventListener('click', listener, false);
elem.removeEventListener('click', listener, false);According to the DOM spec, the second removeEventListener should do nothing. However, with zone.js loaded it produces the following error message:
Error: Task does not support cancellation, or is already canceled.
at ZoneDelegate.cancelTask (/usr/local/google/home/sjelin/zone.js/test/browser_entry_point.ts:382:24)
at Zone.cancelTask (/usr/local/google/home/sjelin/zone.js/test/browser_entry_point.ts:292:45)
at zoneAwareRemoveEventListener (/usr/local/google/home/sjelin/zone.js/test/browser_entry_point.ts:970:25)
at HTMLBodyElement.removeEventListener (eval at createNamedFn (/usr/local/google/home/sjelin/zone.js/test/browser_entry_point.ts:1051:18), <anonymous>:3:46)
at Object.<anonymous> (/usr/local/google/home/sjelin/zone.js/test/browser_entry_point.ts:2354:19)
Basically, the problem is that the patched removeEventListener will cancel the task, but never removes it from the list of registered tasks. So when the second removeEventListener happens it tries to cancel the task again, leading to the problem. I suggest we start removing it from the list of registered tasks, unless there is a reason it has to stay there.
Activity
mhevery commentedon Mar 18, 2016
Sounds good to me.
arsenys commentedon Mar 18, 2016
I have the exactly the same problem. I have an
Angular2app with Semantic-UI. After upgradingzone.jsfrom 0.5.x to 0.6.x almost every Semantic-UI component, such as modal window or dropdown throws theSafeSubscribererrors, whether itsTask does not support cancellation, or is already canceled.orundefined is not an object (evaluating 'task.zone')errors fromSafeSubscriber.fix(browser/utils): calling removeEventListener twice with the same a…