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Problem Cancelling Route

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Sean
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Sean asked on 23 Jan 2014, 03:51 PM
I am working on creating a new application using the Kendo SPA framework.  One must-have feature is the ability to cancel navigation to a route, for example - don't allow the user to navigate away if the current has unsaved changes.

According to the documentation, this should be as simple as calling e.preventDefault() in the router's change event.  And this does work in the simplest scenario - if you wire up the change event and call preventDefault, the route will be cancelled, you stay on the current view, and the url is reverted back to it's original value.

However, I feel that is overly simplistic.  In reality, you would never simply just cancel the route.  You need to make a call to see if there are unsaved changes so that you can determine whether or not the navigation is allowed.  And this is where my problem lies.

In my scenario, I have a callback that is executed in the router change event that checks to see if the navigation is allowed.  If I hit a route that I cannot leave, then I call e.preventDefault and the view does not change (which is good), but the route does not revert back to the original value (which is bad).  So now the wrong url is showing in the browser.  What's worse is that if I now attempt to navigate to a different route, this will cause an infinite loop where the change event keeps firing and being cancelled, which locks up the browser.

I have created an example in JS Bin that demonstrates this behavior - http://jsbin.com/EXARiTiJ/10.  Here are the steps to recreate the issue:
  1.  When the page loads, it will first navigate to the Home view
  2.  Click on "Orders" to navigate to the Orders view.  This will navigate correctly and update the url appropriately.
  3.  Click "Products" to navigate to the Products view.  Again, this will navigate correctly and update the url.
  4.  Click "Orders" to navigate back to the Orders view.  The code in the change event will call preventDefault and this will trigger the error condition. The Products view will remain visible, but the url now shows "/orders" - however, it should still show "/products".
  5.  Now click "Home" to try to navigate to the Home view.  Be warned though, this will now create an infinite loop and lock up the browser.

It seems like this is a bug with the router, but maybe I am missing something.  Is there a different way that I should be handling canceling the route navigation?  If this is a bug, I would like to know if there is a workaround/fix that can be implemented, since this feature is a must-have for my application. 

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Kiril Nikolov
Telerik team
answered on 24 Jan 2014, 11:26 AM
Hi Sean,

Thank you very much for bringing this to our attention.

This is indeed a bug and I have logged it in our internal bug tracker, so expect a fix to be published soon.

As a small gesture of gratitude I have updated your Telerik Points balance.

Regards,
Kiril Nikolov
Telerik
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Sean
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answered on 24 Jan 2014, 05:21 PM
Kiril,
Thanks for the response.  Do you know how long it will be before a fix is available?  Will it be included in the Q3 Update 1 package, or would it be a separate patch?  Also, is there a manual workaround until the bug is addressed?

The reason I ask is that this is a critical feature for my application.  If I cannot get a fix quickly then I will have to use a different router.  I have used Sammy in the past (and paired it with the Kendo controls), but now that Kendo has it's own router my preference would be to utilize the full suite of Kendo functionality.

Please let me know if there is a way around this issue and the ETA on the fix.

Thanks,
Sean
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Kiril Nikolov
Telerik team
answered on 27 Jan 2014, 10:05 AM
Hello Sean,

The issue has been fixed and the patch will be available with the next internal build of Kendo UI, as we were not able to add it on time for the current release. A manual workaround is not available, as there were a lot of changes, and the fix itself is fairly complex and required a lot of changes. 

Regards,
Kiril Nikolov
Telerik
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Kiril Nikolov
Telerik team
answered on 27 Jan 2014, 12:03 PM
Hello Sean,

The issue has been fixed and the patch will be available with the next internal build of Kendo UI, as it was fixed after the current version was released. A manual workaround is not available, as there were a lot of changes, and the fix itself is fairly complex and required a lot of changes. 

Regards,
Kiril Nikolov
Telerik
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Sean
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answered on 20 Mar 2014, 01:22 PM
I had validated that the fix in the internal build addressed my issue, but I was waiting for the official Q1 2014 release since the internal build contains a disclaimer that the code is not for production.  I have upgraded to the Q1 2014 release and the bug is fixed as expected.  Thanks.
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