Allow transform to have supply layout defaults handler

[etpinard]

a requirement for #1099

cc @rreusser

[etpinard]

@rreusser I chose to only pass transitionData to transform module supplyLayoutDefaults, because that's the only place where we need them at the moment.

[rreusser]

Looks good to me. Only exception is in plot_api/register.js. Can we add hasSupplyLayoutDefaults to the check?

[etpinard]

Can we add hasSupplyLayoutDefaults to the check?

By check, you mean something like:

if(typeof newModule.supplyLayoutDefaults !== 'function') {
  throw new Error('supplyLayoutDefaults method is not a function');
}

?

Otherwise, supplyLayoutDefaults method should be very much optional.

[rreusser]

I was referring to the fact that a transform that only has supplyLayoutDefaults (as this one does) fails unless it has a dummy no-op for either calcTransform or transform. That's easy enough at least. I have no strong feelings here.

[rreusser]

[etpinard]

unless it has a dummy no-op for either calcTransform or transform.

I would prefer keeping this as such. Transform modules should transform the data using .transform or .calcTransform.

[rreusser]

Agreed, though the current use-case is an exception to that rule. I give it the 💃 though.

[rreusser]

🎉 thanks!