json/blueprint/codegen/schema

Generate native records and ordinary typed codecs from a closed-object schema.

This development-time module returns source; the caller writes, formats and compiles it. Generated applications need only json_blueprint. Retain the root codec when reusing it, as with a handwritten codec.

Supported children are strings, booleans, integers, exact numbers, inclusive ranges, objects, lists, pairs and nullable values. Optional nullable fields use Option(Option(a)) to distinguish missing, null and a supplied value. Enums, unions and unconstrained values return located errors. Native Int projection retains the runtime codec’s limits. BEAM-only integer bounds produce source that must be checked for the intended target; JavaScript cannot safely use those bounds. Exact Number does not use floating-point conversion.

Only the root <name>_codec() accessor is public. Root and nested records are public. Wire names are preserved; native names normalize codepoints. Uppercase ASCII letters each start an underscore-separated word. Delimiter runs collapse, digit-leading names gain field_, and keywords gain _. Empty names and collisions fail rather than silently renaming fields.

import json/blueprint/codegen/schema
import json/blueprint/contract
import json/blueprint/value

pub fn generate_order() {
  let assert Ok(contract) =
    contract.parse(
      "{\"$schema\":\"https://json-schema.org/draft/2020-12/schema\",\"type\":\"object\",\"properties\":{\"orderId\":{\"type\":\"string\"}},\"required\":[\"orderId\"],\"additionalProperties\":false}",
      value.default_limits(),
    )
  schema.compile("generated/order", "order", contract.schema(contract))
}

pub type CompileError {
  InvalidModuleName(module_path: String, reason: String)
  InvalidRootName(name: String, reason: String)
  InvalidFieldName(
    path: List(codec.PathSegment),
    wire_name: String,
  )
  NameCollision(
    name: String,
    first: NameOrigin,
    second: NameOrigin,
  )
  UnsupportedShape(
    path: List(codec.PathSegment),
    kind: UnsupportedKind,
  )
}

pub type NameOrigin {
  SchemaLocation(List(codec.PathSegment))
  ReservedName
}

pub type UnsupportedKind {
  NonObjectRoot
  StringEnum
  TaggedUnion
  AnyValue
  UnknownShape
}

pub fn compile(
  module_path: String,
  name: String,
  schema: codec.Schema,
) -> Result(codegen.GeneratedModule, CompileError)