Document optimisticData and rollbackData

[garrettg123]

I just found out that you can do this for optimistic updates. This is amazing and should be documented:

const completeTaskMutationResult = api.task.complete.useMutation({
  onMutate(variables) {
    const updatedTask = {
      ...task,
      completedDate: variables.isCompleted ? new Date() : null,
    } satisfies Task

    return {
      optimisticData: updatedTask,
      rollbackData: task,
    }
  }
})

[klis87]

Did you see this - https://github.com/klis87/normy/tree/master/packages/normy-react-query#optimistic-updates-arrow_up ?

By the way, you could even do something like this:

const completeTaskMutationResult = api.task.complete.useMutation({
  onMutate(variables) {
    const updatedTask = {
      id: task.id,
      completedDate: variables.isCompleted ? new Date() : null,
    } 

    return {
      optimisticData: updatedTask,
      rollbackData: task,
    }
  }
})

, because you need to pass only attributes which are changed (plus identifier you use for objects). Your way works as well, just curiosity.

You might be also interested in #11 - rollbackData could be calculated automatically based on optimisticData, as all it really should be is a denormalized object based on the same structure as optimisticData object.