reactormonk/purescript-rave

A standard stack for PureScript

Rave

The base type of this library is Rave, which is short for Reader, Aff, Variant. Combined, Rave is a standard stack for PureScript application development. It implements ReaderT and Checked Exceptions. Rave does not support interpeters, but it would be possible to have purescript-run interpret into Rave.

newtype Rave r v e = Rave (ReaderT r (ExceptV v Aff) e)

ReaderT

The ReaderT part allows you to pass configuration along to your application without having to do so manually, which tends to clutter your codebase.

type Config =
  { port :: Int
  , host :: String
  , tokenInfoUrl :: String
  , elasticSearchUrl :: String
  }

config :: Config
config =
  { port: 8080
  , host: "localhost"
  , tokenInfoUrl: "http://localhost:8081/tokeninfo"
  , elasticSearchUrl: "http://localhost:9200"
  }

With Rave and partial records, this code can be rewritten as

config =
  { port: 8080
  , host: "localhost"
  , databaseString: "postgresql://postgres@localhost"
  }

main = runRave (RProxy :: _ ()) config do
  dbConnection <- openConnection
  startServer $ { dbConnection: DbConnection, host: config.host, port: config.port }

openConnection :: forall r. Rave { databaseString :: String | r } () DbConnection
startServer :: forall r. Rave { port :: Int, host :: String, dbConnection :: String | r } () -> Aff ()

Variant (checked exceptions)

Java has given checked exceptions a bad reputation. In PureScript, they have a comparatively low cognitive and LoC overhead.

Aff (effect)

Aff is a good default effect monad for any application. You may hit a few corner cases with JavaScript APIs having timing issues with privileges (e.g. window.open), but 99% of the cases, it should be fine.