OnDemandGrid sometimes removes updated rows

[dmartin-gh]

I encountered this issue while using an OnDemandGrid backed by a dojo.store.Observable/dojo.store.Memory combo. When an entry is updated and it needs to jump from one result set to another, it will sometimes get removed from the grid entirely.

I've uploaded a tar.gz archive containing a minimal example which reproduces the error. Load the page and inspect the main.js file. It contains more information about the bug and the exact steps to reproduce it.

http://tinyurl.com/8nyubby (observable_bug.tar.gz 32MB)

[justindoherty]

I believe I've encountered this same issue 6 months ago where items were disappearing from my grid. I had opened two bugs with dojo regarding the issue.

http://trac.dojotoolkit.org/ticket/15227
http://trac.dojotoolkit.org/ticket/15228

[amuraco]

Were you by any chance using the Pagination extension, I saw similar behavior with Observable(JsonRest) and pagination, and managed to fix it in the Paginator.

[dmartin-gh]

I don't have the Paginator mixin enabled in my web app nor the reduced reproduction case that I linked above. With the way our web application is intended to be designed, pagination would not fit our feature requests. I am using a JsonRest store instead of a Memory store in our web app, but the issue is reproducible with both.

Neither of the two tickets above directly address the issue here. What's happening is an item is updated in the second result set and needs to be resorted such that it ends up in the first result set. The resulting observer calls look something like:

// result set 1
observer(obj, -1, 0)
// result set 2
observer(obj, 4, -1)

In this case it should have been moved from the 4th position in the second result set to the front of the first result set. During the first observer callback this happens just fine; if you pause the page at this point the row has been moved in the DOM and everything looks good. Next the second observer is called and at this point dgrid/List fails to recognize that it was moved to another result set. It simply deletes the row's node from the DOM. This can be temporarily fixed (as we have done) by patching dojo.store.Observable() to always do removal callbacks before addition callbacks, but I don't think this is a good long-term fix.

I'm not entirely convinced that the issue here is with dojo.store.Observable(). Is it intended in the design for the result sets to change size over time? Does it matter that it tells the grid that an object was added to one result set and then removed from another (in that order)? The issue may simply be that dgrid/List is removing the item when it should have checked to see that it was moved to another result set already.

[myklt]

frostedcheerios, were You able to find a better workaround than patching dojo/store/Observable? As I see, Observable hasn't been changed with Dojo v1.9.

I can also reproduce the same problem with TODO sample ( http://dojofoundation.org/packages/dgrid/demos/todo/ ) by adding some todos, refreshing the page and updating them. If I click on last added todo - it is removed from grid.

[dmartin-gh]

I have not had a chance to see if kriszyp's changes in b234c63 have fixed this issue in the master. Internally we're still using the older version of dgrid with the patch to dojo/store/Observable.

[kfranqueiro]

This should be resolved in dgrid 0.3.13 and later due to fixes relevant to #701 and #714.