Question

我正在尝试在我的系统上编译this示例代码。当我尝试用ghc Chat.hs编译聊天模块时，ghc给了我这个：

Chat.hs:76:39:
    Couldn't match expected type `Network.Wai.Request'
                with actual type `wai-0.4.3:Network.Wai.Request'
    In the second argument of `eventSourceApp', namely `req'
    In the second argument of `($)', namely `eventSourceApp chan req'
    In a stmt of a 'do' expression:
        res <- lift $ eventSourceApp chan req

我在OS X Snow Leopard上并清理（一切？）除了Haskell平台之外：

rm -r ~/.cabal
rm -r ~/.ghc
rm -r ~/Library/Haskell

并从hackage重新安装了yesod和wai-eventsource。

据我所知，错误来自依赖性问题。

    wai
    Synopsis: Web Application Interface.
    Default available version: 1.0.0
    Installed versions: 0.4.3, 1.0.0
    Homepage: https://github.com/yesodweb/wai
    License:  BSD3

如果yesod-0.9.4.1要求wai == 0.4。*，wai-eventsource-1.0.0要求wai＆gt; = 1.0。

所以，我的问题是：是否有可能让这个例子（使用yesod的正式版本）立即工作？随着所有的变化，yesod项目正在经历atm？我是否必须更加精确地安装我尝试安装的版本，如果是，请如何安装？

编辑：

我消灭了~/.ghc（或实际上遵循here更严格的方法，以防万一）并试图用一个单独安装软件包 cabal install yesod wai-eventsource导致（不完整）：

Resolving dependencies...
cabal: cannot configure yesod-0.9.4.1. It requires wai ==0.4.* and warp ==0.4.*
For the dependency on wai ==0.4.* there are these packages: wai-0.4.0,
wai-0.4.1, wai-0.4.2 and wai-0.4.3. However none of them are available.
wai-0.4.0 was excluded because wai-eventsource-1.0.0 requires wai >=1.0
...
wai-0.4.3 was excluded because wai-eventsource-1.0.0 requires wai >=1.0
For the dependency on warp ==0.4.* there are these packages: warp-0.4.0,
warp-0.4.0.1, warp-0.4.1, warp-0.4.1.1, warp-0.4.1.2, warp-0.4.2, warp-0.4.3,
warp-0.4.3.1, warp-0.4.4, warp-0.4.5, warp-0.4.6, warp-0.4.6.1, warp-0.4.6.2
and warp-0.4.6.3. However none of them are available.
warp-0.4.0 was excluded because wai-eventsource-1.0.0 requires warp >=1.0
...
warp-0.4.6.3 was excluded because wai-eventsource-1.0.0 requires warp >=1.0

在此之前（单独安装yesod和wai-eventsource）我尝试了ghc -hide-package wai-1.0.0 Chat.hs，

Chat.hs:77:39:
Couldn't match expected type `wai-1.0.0:Network.Wai.Request'
            with actual type `Network.Wai.Request'
In the second argument of `eventSourceApp', namely `req'
In the second argument of `($)', namely `eventSourceApp chan req'
In a stmt of a 'do' expression:
    res <- lift $ eventSourceApp chan req

Answer 1

我认为您需要取消注册（或隐藏）wai 1.0.0。目前的Yesod正在使用wai 0.4，这是不匹配的来源。（一旦更新的Yesod发布，这个问题就会消失。）

或者，您可以再次清除〜/ .ghc文件夹并运行cabal install yesod wai-eventsource，这应该只会自动安装兼容版本。

编辑：您还需要隐藏wai-eventsource，还可能隐藏其他一些内容。最简单的方法是运行ghc-pkg unregister wai-eventsource-1.0.0 --force。

Yesod wai-eventsource示例。包依赖问题？

1 个答案: