dom-repeat filter/sort needs to be able to observe parent scope

[mbleigh]

Right now, the dom-repeat filter and sort only refire on array mutations or item subproperty changes with the observe attribute. However this ignores a very common use case for filtering and sorting: user-driven changes to filter. Imagine for instance a simple list of items with a "text search" filter:

<template is="dom-repeat" filter="search">
  <span>[[item.name]]</span>
</template>

<script>
Polymer({
  search: function(item) {
    return item.name.toLowerCase().indexOf(this.q.toLowerCase()) >= 0;
  }
});
</script>

In this scenario, there is no way to make the template re-stamp when an external parameter changes (e.g. q in the example).

[mbleigh]

Note that because of this limitation I am currently manually calling through to the private _render() method in my app code. I didn't see any other way to achieve the desired effect.

[kevinpschaaf]

Since dom-repeat isn't bound to that data (q in your example), it won't receive notifications for changes to it (as opposed to items, which is why the convenience observe property is possible).

For now, the pattern will be for external dependencies of sort/filter, the user will need to observe those properties and call render() manually to refresh the list. This doesn't quite work right now (as you noted), but I'll push a fix this morning to make that go.

[euclid1990]

@kevinpschaaf How to call render() manually from below code:

<template id="resultList" is="dom-repeat" items="{{ schedules }}" filter="filterRoom" as="schedule" index-as="scheduleId">
...
</template>

???

[kevinpschaaf]

@euclid1990

this.$.resultList.render();

Call that after you change any external dependencies to the filterRoom function.