使用镜头捕捉多个异常

问题描述

我正在将Lens与Amazonka一起使用来处理错误，但是我很难处理错误：

doSignup e p = (AWS.send $ AWS.signUp "secret" e p)
    $> Right ()
    & catching_ AWS._UsernameExistsException (return $ Left AlreadyExistingEmail)
    & catching_ AWS._InvalidPasswordException (return $ Left WeakPassword)
    & catching  AWS._SertviceError (return . UnkNownSignUpError)

data SignUpError where
  AlreadyExistingEmail ::                          SignUpError
  NotAnEmail           ::                          SignUpError
  WeakPassword         ::                          SignUpError
  UnkNownSignUpError   :: forall a. Show a => a -> SignUpError

我很难保持一致的捕捉行为，当抛出_UsernameExistsException时，我得到了Left WeakPassword。

它变得很奇怪，因为当我放下WeakPassword行时它就起作用了。

虽然我得到正确的错误（仅保留最后一行）：

       expected: Right ()
        but got: Left UnkNownSignUpError ServiceError' {_serviceAbbrev = Abbrev "CognitoIdentityProvider",_serviceStatus = Status {statusCode = 400,statusMessage = "Bad Request"},_serviceHeaders = [("Date","Tue,06 Oct 2020 05:38:56 GMT"),("Content-Type","application/x-amz-json-1.1"),("Content-Length","96"),("Connection","keep-alive"),("x-amzn-RequestId","b09210a3-41ed-46ee-af4f-46db58b98695"),("x-amzn-ErrorType","UsernameExistsException:"),("x-amzn-ErrorMessage","An account with the given email already exists.")],_serviceCode = ErrorCode "UsernameExists",_serviceMessage = Just (ErrorMessage "An account with the given email already exists."),_serviceRequestId = Just (RequestId "b09210a3-41ed-46ee-af4f-46db58b98695")}

我尝试使用catches，但handler需要Typeable镜头，不是这种情况。

我该如何使用“类似模式匹配”的方式来处理异常？预先感谢。

解决方法

实际上使用的是Control.Lens.catching而不是Network.AWS.Prelude.catching，它搞砸了异常处理。