haskell – 如何在帖子上生成最近帖子列表时避免依赖循环？

这样可行：

create ["archive.html"] $do
    route idRoute
    compile $do
        posts <- (myRecentFirst gitTimes) =<< loadAll "posts/**"
        let archiveCtx =
                listField "posts" (postCtx allTags allCategories gitTimes) (return posts) `mappend`
                constField "title" "Archives"            `mappend`
                (postCtx allTags allCategories gitTimes)

        makeItem ""
            >>= loadAndApplyTemplate "templates/archive.html" archiveCtx
            >>= loadAndApplyTemplate "templates/default.html" archiveCtx
            >>= relativizeUrls

在archive.html中创建最近的帖子列表;这是沼泽标准,它来自我认为的其中一个教程.除了postsCtx,这有点复杂,但在这里不应该相关.

但是,我想在正常帖子的侧边栏中列出一些最近的帖子.问题在于最近的帖子最终取决于他们自己.我试着从自己生成的列表中排除帖子本身,但我找不到一个好的地方去做.这是我到目前为止所得到的：

match "posts/**" $do
    route $(gsubRoute "posts/" (const "")) `composeRoutes` setExtension "html"
    compile $do
        recents <- (myRecentFirst gitTimes) =<< loadAll "posts/**"
        let postsContext = postCtx allTags allCategories gitTimes `mappend`
                           -- Show recent posts
                           recentsNotSelfField "recents" (postCtx allTags allCategories gitTimes) (return $take 3 recents)

        pandocCompilerWithTransform hblogPandocReaderOptions hblogPandocWriterOptions (titleFixer titles)
            >>= loadAndApplyTemplate "templates/post.html"    postsContext
            >>= loadAndApplyTemplate "templates/default.html" postsContext
            >>= relativizeUrls

recentsNotSelfField :: String -> Context a -> Compiler [Item a] -> Context b
recentsNotSelfField key context items = Context $k _ i ->·
    if k == key then do
        let myId = itemIdentifier i
        strippedItems <- items
        let remains = filter (x -> (itemIdentifier x) /= myId) strippedItems
        return $ListField context remains
    else
        CA.empty

recentsNotSelfField应该生成一个除了本身以外的所有最近的字段,但它似乎没有工作或者它是错误的地方,因为：

Initialising...
  Creating store...
  Creating provider...
  Running rules...
Checking for out-of-date items
Compiling
  [ERROR] Hakyll.Core.Runtime.chase: Dependency cycle detected: posts/computing/contact.md depends on posts/computing/contact.md

到目前为止,我被困住了.

编辑：

我看到Hakyll says “Dependency cycle detected: …”,这是loadPosts做的,所以我尝试了这个：

match "posts/**" $do
    route $(gsubRoute "posts/" (const "")) `composeRoutes` setExtension "html"
    compile $do
        myId <- getUnderlying
        recents <- (myRecentFirst gitTimes) =<< loadAll ("posts/**" .&&. complement (fromList [myId]))
        let postsContext = postCtx allTags allCategories gitTimes `mappend`
                           -- Show recent posts
                           listField "recents" (postCtx allTags allCategories gitTimes) (return $take 3 recents)

        pandocCompilerWithTransform hblogPandocReaderOptions hblogPandocWriterOptions (titleFixer titles)
            >>= loadAndApplyTemplate "templates/post.html"    postsContext
            >>= loadAndApplyTemplate "templates/default.html" postsContext
            >>= relativizeUrls

但这只是让我：

[ERROR] Hakyll.Core.Runtime.chase: Dependency cycle detected: posts/computing/contact.md depends on posts/computing/general/ched.md depends on posts/computing/contact.md

换句话说,最终我最近两次骑自行车.

match "posts/**" $version "recents" $do
    route $(gsubRoute "posts/" (const "")) `composeRoutes` setExtension "html"
    compile $do
        pandocCompilerWithTransform hblogPandocReaderOptions hblogPandocWriterOptions (titleFixer titles)
            >>= loadAndApplyTemplate "templates/post.html"    (postCtx allTags allCategories gitTimes)
            >>= relativizeUrls

match "posts/**" $do
    route $(gsubRoute "posts/" (const "")) `composeRoutes` setExtension "html"
    compile $do
        myId <- getUnderlying
        recents <- (myRecentFirst gitTimes) =<< loadAll ("posts/**" .&&. hasVersion "recents")
        let postsContext = postCtx allTags allCategories gitTimes `mappend`
                           -- Show recent posts
                           listField "recents" (postCtx allTags allCategories gitTimes) (return $take 3 recents)

        pandocCompilerWithTransform hblogPandocReaderOptions hblogPandocWriterOptions (titleFixer titles)
            >>= loadAndApplyTemplate "templates/post.html"    postsContext
            >>= loadAndApplyTemplate "templates/default.html" postsContext
            >>= relativizeUrls

我不得不将listField和recents添加到使用templates / default.html的其他几个地方,但这很简单.

我还必须修改一个使用Identifier来查找从git中提取的时间列表的函数：

-- Pull a file's time out of the list
getGitTimeUTC :: Identifier -> [GitTimes] -> (GitTimes -> UTCTime) -> UTCTime
getGitTimeUTC ident times typeF =
  -- The identifier for the things compiled with the "recents"
  -- version has the identifierVersion "recents",but we don't care
  -- about that since the only reason that exists is to avoid loops,-- so we strip it here for our lookup.
  let fixedIdent = ident { identifierVersion = Nothing }
      timeList = filter (x -> fixedIdent == (gtid x)) times in
    if length timeList /= 1 then
      -- It's not obvious to me how this could occur even in theory; I'd expect it to error out during getGitTimes
      error $"getGitTimeUTC: Couldn't find the time for " ++ (show fixedIdent) ++ " in GitTimes list " ++ (show times)
    else
      typeF $head timeList

结果我没有重复的文件,并且没有问题链接到最近的文件;一切正常.

（编辑：安卓应用网）

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