Function multiSelect

repos/effect/packages/effect/src/unstable/cli/Prompt.ts:1194–1215

(
  options: SelectOptions<A> & MultiSelectOptions
)

  self: Prompt<Output>
) => Effect.Effect<
  Output,
  Terminal.QuitError,
  Environment
> = Effect.fnUntraced(
  function*<Output>(self: Prompt<Output>) {
    const terminal = yield* Terminal.Terminal
    const input = yield* terminal.readInput
    return yield* runWithInput(self, terminal, input)
  },
  Effect.mapError(() => new Terminal.QuitError({})),
  Effect.scoped
)

const getSelectInitialIndex = <A>(choices: ReadonlyArray<SelectChoice<A>>): number => {
  let initialIndex = 0
  let seenSelected = -1
  for (let i = 0; i < choices.length; i++) {
    const choice = choices[i] as SelectChoice<A>
    if (choice.selected === true) {
      if (seenSelected !== -1) {
        throw new Error("InvalidArgumentException: only a single choice can be selected by default for Prompt.Select")
      }
      seenSelected = i
    }
  }