polytropos-aeson

High-performance aeson JSON serialization and deserialization codecs for polytropos open records and variants.

Overview

Unlike GHC.Generics which builds intermediate binary tree nodes ((:*:), (:+:)) during serialization, polytropos-aeson unrolls the flat contiguous SmallArray payload directly into JSON objects and back. Open variants serialize into tagged JSON objects with \(O(1)\) tag dispatch.

Features

• Heterogeneous Record Encoding & Decoding: Automatic ToJSON and FromJSON instances for Record r via compile-time field unrolling.
• Tagged Variant Codecs: Fast \(O(1)\) constructor dispatch encoding variants as {"tag": "Ctor", "contents": payload}.
• Homogeneous Fast Path: Specialized introspection and codec paths for homogeneous records.

Quick Example

{-# LANGUAGE DataKinds #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE OverloadedRecordDot #-}
{-# OPTIONS_GHC -fplugin=Polytropos.Plugin #-}

import Data.Aeson (encode, decode)
import Polytropos
import Polytropos.Aeson ()

type Config = Record '[ "host" := String, "port" := Int ]

main :: IO ()
main = do
  -- Direct serialization without ($) grouping:
  let cfg = REC { host = "localhost", port = 8080 } :: Config
  print (encode cfg)

  -- Functional record update without parentheses:
  let prodCfg = REC_UPD cfg { host = "prod.internal" }
  print (encode prodCfg)

License

Dual-licensed under EUPL-1.2 OR Apache-2.0.