F＃中最常见的错误表示方式是什么 [英] What is the most idiomatic way of representing errors in F#

问题描述

我正在研究F＃项目，我想知道使用F＃中的 Result 类型返回域错误的最佳实践是什么？我认为有几种解决方法：

I'm working on F# project and I wonder what is the best practice to return domain error using Result type in F#. There are several ways of doing it which I consider:

继承的异常

type DomainException(message) =
    inherit Exception(message)

type ItemNotFoundException(item) =
    inherit DomainException(sprintf "Item %s is not found" item)

let findItem item =
    match item with
    | Some x -> Ok x
    | None -> Error(new ItemNotFoundException("someitem"))

自定义记录类型

type DomainError =
    { Name : string
      Message : string }

let findItem item =
    match item with
    | Some x -> Ok x
    | None ->
        Error({ Name = "ItemNotFound"
                Message = "Item someitem is not found" })

记录类型的区分联合

type DomainErrorTypes =
    | ItemNotFoundError of DomainError
    | ItemInvalidFormat of DomainError

let findItem item =
    match item with
    | Some x -> Ok x
    | None ->
        { Name = "ItemNotFound"
          Message = "Item someitem is not found" }
        |> ItemNotFoundError
        |> Error

那么哪种方法更惯用且方便使用？我也很高兴看到更好的选择。

So which way is more idiomatic and convenient to use? I also will be happy to see better options.

推荐答案

通常，这将是一个有区别的联合。每个错误都需要不同的详细信息来伴随消息。例如：

Typically it would be a discriminated union. Every error requires different details to accompany the message. For instance:

type DomainErrorTypes =
| ItemNotFound of ItemId
| FileNotFound of string
| InvalidFormat of format
| IncompatibleItems of Item * Item
| SQLError of code:int * message:string
| ...

您还可以捕获一些例外情况（不一定是全部）：

You can also capture some exceptions (not necessarily all):

| ...
| Exception of exn

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