gilligan/dhall-to-cabal

Compile Dhall expressions to Cabal files

dhall-to-cabal -- generate Cabal files from Dhall expressions

Work in progress - there's plenty more to do here. Feel free to get stuck in and submit pull requests!

dhall-to-cabal takes a Dhall expression that evaluates to a record containing fields fo a .cabal file and produces a valid .cabal file. For a large example, this very project has a dhall-to-cabal.dhall file which generates dhall-to-cabal.cabal. Don't be put off by the verbosity, issue #3 tracks providing a much nicer standard library (in Dhall-land) to generate these Dhall expressions. Such is the beauty of having a powerful language behind us!

y tho?

I love Cabal, and .cabal files aren't bad, but they are hardly great either. A major limitation is the lack of a way to import things. This leads to code duplication and repetition, and we all know this is a bad thing. The means of abstraction in a cabal file a pretty rudimentary too - why not just give us proper variables and let us figure out how best to abstract things?

If you accept the above argument, then Dhall-to-Cabal might be of interest to you. This approach enables a few nice things:

• The ability to share your Cabal configuration files inside the configuration of other services without having to write a bunch of Haskell code. It's just Dhall, so you can just import it and manipulate it as you'd like.

• The ability for projects to provide a template that can be included by users. Large frameworks such as Yesod could provide a yesod.dhall that is imported by users. One might imagine:

  let yesodProject = http://.../yesod in
  yesodProject {
    name = "my-cool-website",
    handlers = [ "Handler.Index", "Handler.CoolThing" ],
    models = [ "Model.Cat", "Model.Dog" ]
  } 

  and have yesodProject turn this into a valid Cabal plan, bringing down Yesod, enabling type extensions, turning on specific warnings, all that goodness.

  We can also see the desire to have this import/reuse functionality in core libraries. The network opens with a stanza about how you have to add the library to your cabal file which is totally non-standard. Just give me an expression to import, and then I don't have to worry about the details!