"Failed to compute" error because of unexpected operation inside #if

Question

Here is the problem (Ractive.js v0.7.3): http://jsfiddle.net/Inversion/hLym2xcy/

r = new Ractive
    el: 'cont'
    template: '''
        {{#task.options}}
            {{#if pros}}
                inside if
                {{#each filter(.pros)}}<li class='{{set_class(.)}}'>+{{.v}}</li>{{/each}}
            {{/if}}
        {{/task.options}}
    '''
    data:
        task:
            options: [{pros:[{v:1}]}]
        set_class: (o)-> o.v
        filter: (arr)-> console.log(arr);arr || []

setTimeout(
    -> r.set('task.options.0.pros', undefined)
    2000
)

On r.set operation "inside if" is not printed out as expected, but #each tries to work with an undefined array which is not expected.

I cannot guarantee presence of an pros array and that's why I used {{#if pros}} to do not use it, but seems like it doesn't work.

console.log(arr) is added to see if filter is actually called, and it is. Also when I try to return [] from the filter it still calls set_class which is unexpected because there is nothing to iterate.

Is there a way to overcome these unexpected problems?

Thanks!

Answer 1

Seems like it is a known problem and will be fixed in v0.8