Is it possible to share informations between the mutateFn and onMutate ?

[myagoo]

Hi everyone, I'm using react-query with firebase, so far, so good.

But I encountered an issue when implementing optimistic updates

const [updateTodo] = useMutation(async (newTodo) => {
  const ref = firebase.database().ref('todos').push(newTodo)
  console.log(ref.key) // Here I have a todo ID before any network operation
  return await ref
 }, {
   // When mutate is called:
   onMutate: newTodo => {
     queryCache.cancelQueries('todos')
     const previousTodos = queryCache.getQueryData('todos')
     queryCache.setQueryData('todos', old => [...old, newTodo]) // Issue here : I would like to access ref.key
     return () => queryCache.setQueryData('todos', previousTodos)
   },
   onError: (err, newTodo, rollback) => rollback(),
   onSettled: () => {
     queryCache.invalidateQueries('todos')
   },
 })
 const handleTodoAddClick = () => updateTodo(pendingTodo)

I thought about a way to do it but I'm not sure about how it will integrate with react-query

const [updateTodo] = useMutation(async (newTodo) => {
  const ref = firebase.database().ref('todos').push(newTodo)
  queryCache.cancelQueries('todos')
  // Get previous todos in case of rollback
  const previousTodos = queryCache.getQueryData('todos')
  queryCache.setQueryData('todos', old => [...old, {id: ref.key, ...newTodo}])
  try{
    await ref
  }catch(error){
    // rollback
    queryCache.setQueryData('todos', previousTodos)   
  }finally{
    queryCache.invalidateQueries('todos')
  }
 })