haskell-frontmatter

Attoparsec parsers for YAML frontmatter as used in Jekyll. Because of how Data.Yaml is implemented using Data.Aeson, the Data.Yaml.Frontmatter.frontmatterYaml instance of Parser works with YAML and JSON.

Installation

This actually won’t work right now

$ stack install frontmatter

Usage

import Data.Frontmatter
import Data.Yaml (Value)

main = ByteString.readFile "something.md" >>= parseYamlFrontmatter >>= \case
    Done ri fm -> do
        print (fm :: Value) -- aeson object in the frontmatter (the explicit
                            -- type required because the parser will return
                            -- anything with a FromJSON

        putStrLn ri         -- rest of the document
    _ -> error "Parse failure"

See the haddocks for more information. Essentially exports an Attoparsec parser and some helpers. Usage examples also available at the test directory.

Why?

I’m working on the Haskell workshop tool workhs. In my mind, using markdown file names as metadata is a very sensible decision. However, I’d like for tutorial writers to be able to override metadata. Then, Jekyll’s YAML frontmatter format is a great choice:

• It’s familiar
• It’s very, very easy to implement

License

This software is published under the MIT license. For more information refer to the LICENSE file.