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CDDL to Kotlin

Generate Kotlin type definitions from CDDL as data classes, typealiases and enums.

cddl2kotlin converts a parsed CDDL schema into Kotlin source code. Groups become data classes, named assignments become typealiases, and choices become enum classes or sealed interfaces.

Install

Use the CLI:

npm install cddl2kotlin

Use the programmatic API:

npm install cddl cddl2kotlin

What It Generates

cddl2kotlin maps common CDDL constructs into idiomatic Kotlin, including:

  • named CDDL assignments to typealias declarations
  • groups to data class declarations (empty groups become a plain class)
  • optional group fields to nullable types with a = null default
  • arrays to List<T>
  • record groups (*text => T) to Map<String, T>
  • string-literal choices to enum class declarations
  • choices of named types to sealed interfaces with wrapper data classes

It also normalizes names for Kotlin code by turning type names into PascalCase, field names into camelCase (escaping Kotlin keywords with backticks) and enum constants into UPPER_SNAKE_CASE.

Because Kotlin has no structural union or intersection types, inline unions of more than one concrete type fall back to Any?, and group mixins (unnamed group references) are flattened by inlining the referenced group's fields.

CLI

The CLI reads a CDDL file and writes generated Kotlin code to stdout, so the normal workflow is to redirect the output into a .kt file.

npx cddl2kotlin ./path/to/schema.cddl > ./Types.kt

Show help:

npx cddl2kotlin --help

Programmatic API

The package exports a single transform() function. It accepts the parsed CDDL AST and returns the generated Kotlin source as a string.

import { parse } from 'cddl'
import { transform } from 'cddl2kotlin'

const ast = parse('./schema.cddl')
const kotlin = transform(ast)

console.log(kotlin)

Example

Input CDDL:

person = {
  name: tstr,
  age: uint,
  ?nickname: tstr,
}

Generated Kotlin:

data class Person(
    val name: String,
    val age: Long,
    val nickname: String? = null
)

Notes

  • Generated files include a header comment with the cddl2kotlin version used.
  • The CLI validates that the input file exists before attempting to parse it.

If you want to contribute fixes or improvements, see the repository contributing guide.