Filter-transformed data not displaying markers correctly

[rreusser]

Seen on current master branch. Live example: http://codepen.io/rsreusser/pen/GjdxLL?editors=0010

Given this trace:

[{
  x: [1, 2, 3],
  y: [1, 2, 4],
  ids: ['a', 'a', 'a'],
  transforms: [{
    type: 'filter',
    filtersrc: 'ids',
    operation: '{}',
    value: ['a']
  }]
}]

I'd expect it to show markers at all three points. It only shows one marker. I'm not missing or confusing something, am I?

[rreusser]

Reason is obvious in hindsight: ids is equivalent to a d3 key property. The ids aren't unique, so it only draws one point.

[rreusser]

Closing this in favor of moving remaining discussion to #1028.