Function createOptimisticAction

packages/db/src/optimistic-action.ts:54–81

(
  options: CreateOptimisticActionsOptions<TVariables>,
)

 * @returns A function that accepts variables of type TVariables and returns a Transaction
 */
export function createOptimisticAction<TVariables = unknown>(
  options: CreateOptimisticActionsOptions<TVariables>,
) {
  const { mutationFn, onMutate, ...config } = options

  return (variables: TVariables): Transaction => {
    // Create transaction with the original config
    const transaction = createTransaction({
      ...config,
      // Wire the mutationFn to use the provided variables
      mutationFn: async (params) => {
        return await mutationFn(variables, params)
      },
    })

    // Execute the transaction. The mutationFn is called once mutate()
    // is finished.
    transaction.mutate(() => {
      const maybePromise = onMutate(variables) as unknown

      if (isPromiseLike(maybePromise)) {
        throw new OnMutateMustBeSynchronousError()
      }
    })

    return transaction
  }
}