Automatically read config.json from the current directory.

Automatically discover and parse a config.json file in the current working directory or any of its parent directories. No need to manually pass file paths. Built on top of aeson, it provides a simple `getConfig :: FromJSON a => IO a` function that also supports default values when fields are missing in the JSON file.

e9571-config-reader-haskell

A tiny, zero-configuration Haskell library that instantly reads a config.json file from the current working directory.

Out-of-the-box, no setup required.
Just drop a config.json file next to your executable and start using the library — it just works.

Usage (two steps)

1. Create a config.json file in the same directory as your program:

   {
     "host": "127.0.0.1",
     "port": 8080
   }
   

2.    {-# LANGUAGE OverloadedStrings #-}
   
      import E9571.ConfigReader
      import Data.Aeson
   
      data Config = Config { host :: String, port :: Int } deriving Show
   
      instance FromJSON Config where
          parseJSON = withObject "Config" $ \o -> Config
              <$> o .: "host"
              <*> o .: "port"
   
      main :: IO ()
      main = do
          cfg <- loadConfigOrDie :: IO Config   -- automatically reads ./config.json
          putStrLn $ "Server starting at " ++ host cfg ++ ":" ++ show (port cfg)
   

Features

• Automatically looks for ./config.json at runtime
• No file paths, no command-line flags, no environment variables
• Works with any FromJSON instance
• Helpful error messages when the file is missing or malformed
• Only depends on aeson

Installation

cabal install e9571-config-reader-haskell

Source: https://github.com/e9571/e9571-config-reader-haskell Hackage: https://hackage.haskell.org/package/e9571-config-reader-haskell

Enjoy the simplicity!