英文:
haskell use file argument from command line with ".."
问题
使用 命令行解析器 提供一个包含文件名参数的字符串，而在这种情况下是 "../somedir"。如何将此字符串转换为类型安全的 相对路径目录，以便稍后与当前目录组合？
relDir1 <- parseRelDir fp
会引发错误（如描述中所指出的），因为它 "包含表示父目录的 .. 路径组件"。
尝试首先将当前目录与命令行中的字符串结合起来，如：
relDir2 <- parseRelDir (currDir </> fp)
返回相同的错误。
我找到了一个 "hack"，使用来自 FileSystem.Path 的 collapse，它需要一个 decodeString 和一个 encodeString，用于在字符串（又名 FilePath）和特殊使用的 FilePath 之间转换：
combPath = toFilePath currDir </> (locationDir $ flags) :: FilePath
collPath = collapse . decodeString $ combPath
absdir = makeAbsDir . encodeString $ collPath :: Path Abs Dir
但是我想肯定有一个更好的方法来处理这个常见任务，假设在某处会有一个更好的方法。
英文:
Using a command line parser gives a string containing a filename argument, which in this case is "../somedir". How to convert this string into a typesafe Path Rel Dir from Path to combine later with the current directory?
relDir1 <- parseRelDir fp
throws an error (as indicated in the description, because it "contains a .. path component representing the parent directory")
Trying to combine the currentDir with the String from the command line first, as in
relDir2 <- parseRelDir (currDir </> fp)
returns the same error.
I found a "hack", using collapse from FileSystem.Path, which requires an decodeString and a encodeString to convert from String (aka FilePath) to the special FilePath used:
combPath = toFilePath currDir </> (locationDir $ flags) :: FilePath
collPath = collapse . decodeString $ combPath
absdir = makeAbsDir . encodeString $ collPath :: Path Abs Dir
but assume there is somewhere a better approach to this common task?
答案1
得分: 4
或许你正在寻找canonicalizePath。在 /home/<my-user> 中启动 ghci：
System.Directory> canonicalizePath ".."
"/home"
英文:
Perhaps you are looking for canonicalizePath. Starting ghci in /home/<my-user>:
System.Directory> canonicalizePath ".."
"/home"
答案2
得分: 1
你链接到了 Path 包的文档。在该页面上搜索了一下，有 6 处提及了 ..，其中一处明确地回答了你的问题：
> 有时候你会得到包含 ../ 的用户输入。我们采用的解决方案是使用类似于 resolveDir 函数（在 path-io 包中找到）：
> resolveDir :: (MonadIO m, MonadThrow m)
> => Path Abs Dir -> FilePath -> m (Path Abs Dir)
>
> 它将调用 canonicalizePath 函数，该函数会折叠和规范化路径，然后我们使用常规的 parseAbsDir 进行解析，一切就都很顺利了。这个以及类似的函数可能会被添加到 path 包中。
英文:
You linked to the documentation of the Path package. There are 6 mentions of .. if you search that page, and one of them is clearly addressing your question:
> Sometimes you have user input that contains ../. The solution we went
> with is to have a function like resolveDir (found in path-io package):
>
> resolveDir :: (MonadIO m, MonadThrow m)
> => Path Abs Dir -> FilePath -> m (Path Abs Dir)
>
> Which will call canonicalizePath which collapses and normalizes a path and then
> we parse with regular old parseAbsDir and we’re cooking with gas. This
> and others like it might get added to the path package.
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