Event listeners arguments should be (event, d) but in some projects are (d, index)

[caesarsol]

we had some notifications that in some cases the defined events listeners were called with (d, i) as parameters, and no events.

we are relying on d3-selection (added as a peerDependency) for the event listeners, and after checking I discovered that the problem was caused by which version of d3-selection is used in the project (which is sometimes not strictly linked to which version of d3 is used, unfortunately):

• in d3-selection v1.4.1 the rule was:

  When a specified event is dispatched on a selected element, the specified listener will be evaluated for the element, being passed the current datum (d), the current index (i), and the current group (nodes)

• in d3-selection v2.0.0 (and hence v3.0.0) that changed:

  When a specified event is dispatched on a selected element, the specified listener will be evaluated for the element, being passed the current event (event) and the current datum (d)

we will need to:

1. clear this out in the README
2. find a reliable solution, maybe backward compatible. possibly add d3-selection as a hard dependency?