atproto_lexicon/decoding

Decode lexicon JSON into the atproto_lexicon/ast types.

Unrecognized keys inside a known def or property are ignored: this module decodes the keys the spec defines and drops anything else, rather than collecting them into a passthrough bag or erroring. Every corpus file used to build this package has zero unrecognized keys, so the choice costs nothing there; it is a real fidelity gap for documents carrying vendor extensions or not-yet-spec’d fields, which would silently lose those keys on a decode/encode round trip. An unrecognized type discriminator (on a def, property, array item or params property) is different: that is a shape we cannot represent at all, so it is a decode error rather than a silent drop.

pub type DecodeError {
  MalformedJson(reason: String)
  InvalidLexicon(
    path: List(String),
    expected: String,
    found: String,
  )
}

pub fn decode_dynamic(
  data: dynamic.Dynamic,
) -> Result(ast.LexiconDoc, List(DecodeError))

pub fn decode_json(
  source: String,
) -> Result(ast.LexiconDoc, List(DecodeError))

pub fn document_decoder() -> decode.Decoder(ast.LexiconDoc)