API change proposal for useTransition

[yuchi]

Description

Since configuration for a transition is usually static or a static composition of functions, it makes sense to define it outside of the component body:

const config = {
  trail: 100,
  from: { opacity: 0 },
  enter: { opacity: 1 },
  leave: { opacity: 0 }
};

const keys = item => item.id;

function MyAnimation({ items }) {
  const transitions = useTransition({ items, keys, ...config });
  // ....
}

The current approach of having a single configuration argument makes this slightly less usefull since you need to spread that static configuration over the object that includes items and keys too.

Proposal

I propose to change the API to this:

useTransition(items, keys, config);

This reduce the need for the creation of a pretty useless object at render time.

Additional note

This makes the API more coherent with useTrail:

useTrail(items.length, config);
useTransitions(items, keys, config);

[drcmda]

Makes sense! The only thing i don't like is that keys is optional right now, here it would take a fixed spot with this approach. On the other hand, maybe we're better off enforcing keys, making users think about this, because default keys (props => props) can fail.

[yuchi]

Willing to accept a PR for this or you want to do it yourself?
I'll just wait for your confirmation on the second keys argument.

[ruggedy]

@yuchi I think it's a good idea. feel free to create a PR for this of course. as this is going to be a breaking change. maybe wait for @drcmda to get back from the holidays.

[yuchi]

Friendly reminder :) still interested in this API change?

[drcmda]

@yuchi you want to make the PR? i think this is a good change - makes total sense to do it that way.

[drcmda]

btw, some new ideas here: #425

[aleclarson]

This was implemented in v8.0.0