fix: assign controller to provided ref for useTransition

packages/core/src/hooks/useTransition.test.tsx

@@ -4,6 +4,7 @@ import { RenderResult, render } from '@testing-library/react'
 import { toArray } from '@react-spring/shared'
 import { TransitionFn, UseTransitionProps } from '../types'
 import { useTransition } from './useTransition'
+import { SpringRef } from '../SpringRef'
 
 describe('useTransition', () => {
   let transition: TransitionFn
@@ -35,6 +36,18 @@ describe('useTransition', () => {
     expect(rendered).toEqual([false])
   })
 
+  it('assign controllers to provided "ref"', async () => {
+    const ref = new SpringRef()
+    const props = {
+      ref,
+    }
+    const children = [<div />, <div />, <div />]
+
+    update(children, props)
+
+    expect(ref.current).toHaveLength(3)
+  })
+
   describe('when "leave" is an array', () => {
     it('unmounts after leave', async () => {
       const props = {

packages/core/src/hooks/useTransition.tsx

@@ -199,6 +199,7 @@ export function useTransition(
     // The payload is used to update the spring props once the current render is committed.
     const payload: ControllerUpdate<UnknownProps> = {
       ...defaultProps,
+      ref: props.ref,
       delay: (delay += trail),
       // This prevents implied resets.
       reset: false,