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Riccardo Odone
Riccardo Odone

Posted on • Edited on • Originally published at odone.me

Production Drafts for Hakyll Posts

#functional #haskell #hakyll

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Last week I was asked to review a draft of a blog post:

That made me realize I don't have a way to do a similar trick. However, last week I worked on "Adding published to Hakyll Posts". Thus, I already did the hard work on understanding the internals, so I could just sit back and code it.

Up until now the blog worked as follows:

  • Published posts were compiled by Hakyll to posts/*.
  • Drafts were not compiled except when HAKYLL_ENV was set to development.

With the new changes:

  • All posts are compiled by Hakyll.
  • Published posts are compiled to posts/* and appear in the archive.
  • Drafts are compiled to drafts/posts/* but do not appear in the archive.

In particular, only published posts are compiled to posts/*:

- matchMetadata "posts/*" (isDevelopmentOrPublished env) $ do + matchMetadata "posts/*" isPublished $ do  route $ setExtension "html"
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Drafts are compiled to drafts/posts/*. Also, when compiling the URL to the draft is printed:

matchMetadata "posts/*" (not . isPublished) $ do let draftPath = ("drafts/" <>) . (`replaceExtension` "html") . toFilePath route . customRoute $ draftPath let putDraftUrl path = traverse_ (unsafeCompiler . putStrLn) [ "----DRAFT----", (previewUrl <>) . draftPath . itemIdentifier $ path, "-------------" ] compile $ pandocCompiler >>= loadAndApplyTemplate "templates/post.html" postCtx >>= loadAndApplyTemplate "templates/default.html" postCtx >>= relativizeUrls >>= (\x -> putDraftUrl x >> pure x)
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In the archive only published posts are included except when in development:

 create ["archive.html"] $ do route idRoute compile $ do - posts <- recentFirst =<< loadAll "posts/*" + posts <- recentFirst =<< loadAllPublished env "posts/*"
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loadAllPublished :: (Binary a, Typeable a) => [(String, String)] -> Pattern -> Compiler [Item a] loadAllPublished env pattern_ = if isDevelopmentEnv env then all else published where all = loadAll pattern_ published = publishedIds pattern_ >>= traverse load isDevelopmentEnv env = lookup "HAKYLL_ENV" env == Just "development"
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A similar change appears in the Atom feed code:

- =<< loadAllSnapshots "posts/*" "content" + =<< loadAllSnapshotsPublished "posts/*" "content"
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loadAllSnapshotsPublished :: (Binary a, Typeable a) => Pattern -> Snapshot -> Compiler [Item a] loadAllSnapshotsPublished pattern_ snapshot = publishedIds pattern_ >>= traverse (`loadSnapshot` snapshot) publishedIds :: MonadMetadata m => Pattern -> m [Identifier] publishedIds = fmap (fmap fst . filter (isPublished . snd)) . getAllMetadata
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As always, feel free to go ahead and grab the code.

The draft I ended up reviewing was "Functional Fika — Nix and Haskell". Thanks Maxfield for the inspiration and for teaching me what fika is! ☕️

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