haskell - 从 haskeline 中调用网络 IO

Question

我有一个现有程序，它接受命令行参数(用户名、密码、日期)，然后使用 Network.HTTP.Conduit 库将 xml 消息发布到服务器。然后我解析结果，做一些工作并使用 blaze-html 写入文件。

这一切都像一个魅力；但是，我想我应该使用 haskeline 以便密码不可见。我可以创建一个命令行程序来获取用户提供的值并将其打印出来，但如果我调用使用管道的函数，它永远不会返回。

这是有问题的代码:

main = runInputT defaultSettings loop
where 
    loop :: InputT IO ()
    loop = do
        Just username <- getInputLine "WM username: "
        Just password <- getPassword (Just '*') "WM password: "
        Just date     <- getInputLine "Date (YYYYMMDD): "

        outputStrLn "querying WM..."
        clients <- lift $ getWMClients username password
        outputStrLn "successfully retrieved client list from WM..."

        let outHeader = renderHeader date username

        reportString <- mapM  (\x -> createString x clients)  cList

        lift $ writeFile (date ++ "_report.html") (outHeader ++ concat reportString)
        outputStrLn "Done"

函数getWMClients函数为:

getWMClients :: Username -> String -> IO [Client]
getWMClients username password = do
    let f = [Size "-1", Skip "0"]
    let fs = [Select "id",
              Select "status",
              Select "last-name",
              Select "first-name",
             ]
    let query = WMQuery {transaction=SHARE,service=Query,businessObject=CONT,field=f,fields=fs}

    results <- doQuery username (Just password) Nothing (Just query)
    rows <- xmlResultsToMaps results

    let clients = map makeClient rows
    return clients

当我运行该程序时，它卡在“正在查询 WM...”处，我认为 http-conduit 从未真正运行过。关于如何实现这项工作有任何提示吗？

提前致谢，尼尔

Answer 1

您声称它可以在 haskeline 之前使用硬编码的用户名、密码和日期。为了帮助调试，您可能无法将导管提升到 InputT 中。下面的操作还失败吗？ (我没有编译这个，所以请随意修复语法错误...)

-- Isolate the haskeline monad to just the input part:
main = loop
where 
    loop :: IO ()
    loop = do
      (username,password,date) <- runInputT defaultSettings $ do
        Just username <- getInputLine "WM username: "
        Just password <- getPassword (Just '*') "WM password: "
        Just date     <- getInputLine "Date (YYYYMMDD): "
        return (username,password,date)

      putStrLn "querying WM..."
      clients <- getWMClients username password
      putStrLn "successfully retrieved client list from WM..."

      let outHeader = renderHeader date username

      putString <- mapM  (\x -> createString x clients)  cList

      writeFile (date ++ "_report.html") (outHeader ++ concat reportString)
      putStrLn "Done"