Bug in binding in a very specific configuration

[jccazeaux]

I have a very very specific bug that occurs only when you have

• A binder rv-if with some condition
• A binder rv-each on an array inside the rv-if
• Inside the rv-each display array length
  Full exemple here

The bug happens when you

1. Add data to the array (in reality it's a ajax request that adds data)
2. Toggle the rv-if condition to remove the element (in reality the condition is on the length of the array)
3. Reset the array
4. Toggle the rv-if
5. Try to add data...won't work

To get it to work again i must toggle the rv-if twice.

[blikblum]

I managed to find why:

• The each binder will create a observer at scope.pages
• Adding a item, the each binder will create a child view that will reuse the scope.pages observer because of {scope.pages | length}
• Toggling if binder off will unbind the each bindings and will delete the scope.pages observer
• Resetting pages will create a new non observed scope.pages property
• When if bind toggled on the each binder will create a new observer at scope.pages
• When each binder routine is called the child view will be unbind because collection length is different from iterated length -> this will delete the scope.pages observer and reactivity is lost

[blikblum]

If instead of reseting the array, remove one of the item the same bug occurs

[jccazeaux]

Nice, that's a good explanation. Do you see a solution?

[blikblum]

For this specific case yes, but will be symptomatic. The root issue lays deeper.

See http://codepen.io/blikblum/pen/OXBarY

Add some items
Toggle if
Try add more items

[jccazeaux]

I agree, the cause is deep, maybe in the adapter's observce/unobserve functions.
We have many examples, this will make it easier to fix and test!

[jccazeaux]

The issue may be in adapter. See http://codepen.io/jccazeaux/pen/WxaPdm
When no adapter is used in expressions, there is no issue.

[blikblum]

I already fixed in my side. Just need a test

[jccazeaux]

I think i'm close
See here : https://github.com/mikeric/rivets/blob/master/src/adapter.coffee#L97
When unobserve is called on array's keypath, the mutation observers (push, slice...) are deleted regardless of the other observers.

[jccazeaux]

😄
I have a test, i send a PR with it right now

[jccazeaux]

My working fix is to replace

          unless callbacks.length
            delete map.callbacks[keypath]

         @unobserveMutations obj[keypath], obj[@id], keypath

with

          unless callbacks.length
            delete map.callbacks[keypath]
            @unobserveMutations obj[keypath], obj[@id], keypath

It will unobserve mutations only when there are no callbacks left. You have the same?

[blikblum]

The same

[jccazeaux]

Great, i add it to the PR