Flowtype函数会引发错误 [英] Flowtype function can throw error

问题描述

是否有任何方法可以定义一个函数可以明确抛出的错误，显然任何函数都可以抛出错误.但是我想明确定义一个函数旨在引发并且可能根本不返回值.

Is there any way to define that a function explicitly can throw, obviously any function can throw an error. But I'd like to explicitly define that a function is designed to throw and possibly not return a value at all.

async function falseThrow (promise: Promise<any>, error): any {
  let value: any = await promise
  if (!value) throw error
  return value
}

推荐答案

正如Nat Mote在她的回答中强调的那样，无法对流中的检查异常进行编码.

As Nat Mote highlighted in her answer, there's no way of encoding checked exceptions in flow.

但是，如果您愿意稍微更改编码，则可以做一些等效的事情:

However, if you're open to change the encoding a bit, you could do something equivalent:

async function mayFail<A, E>(promise: Promise<?A>, error: E): E | A {
  let value = await promise
  if (!value) {
    return error
  }
  return value
}

现在流程将迫使用户处理错误:

Now flow will force the user to handle the error:

const p = Promise.resolve("foo")
const result = await mayFail(p, Error("something went wrong"))

if (result instanceof Error) {
  // handle the error here
} else {
  // use the value here
  result.trim()
}

如果您尝试做类似的事情

If you try to do something like

const p = Promise.resolve("foo")
const result = await mayFail(p, Error("something went wrong"))
result.trim() // ERROR!

流程会阻止您，因为您尚未检查result是Error还是string，因此调用trim不是安全的操作.

flow will stop you, because you haven't checked whether result is an Error or a string, so calling trim is not a safe operation.

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