Customising Output

Overriding output

If you want to override what KotlinTsGen produces, then you can provide overrides.

By default, Double is transformed to a generated Double alias. We can customise that alias with the mapTypes DSL.

import kotlinx.serialization.builtins.serializer
import io.github.esafak.kotlintsgen.core.*

@Serializable
data class Item(
  val price: Double,
  val count: Int,
)

fun main() {
  val tsGenerator = KotlinTsGenerator()

  tsGenerator.mapTypes {
    Double.serializer() mapsTo typeAlias("Double", ref("double"))
  }

  println(tsGenerator.generate(Item.serializer()))
}

See the type-alias example.

export interface Item {
  price: Double;
  count: Int;
}

export type Double = double; // assume that 'double' will be provided by another library

export type Int = number;

Referencing external types

If a type is already provided by another TypeScript library, use external to reference it without emitting a declaration. Nullable Kotlin properties retain their nullability.

import kotlinx.serialization.builtins.serializer
import io.github.esafak.kotlintsgen.core.*

@Serializable
data class Position(
  val x: Double,
  val y: Double?,
)

fun main() {
  val tsGenerator = KotlinTsGenerator()

  tsGenerator.mapTypes {
    Double.serializer() mapsTo external("double")
  }

  println(tsGenerator.generate(Position.serializer()))
}

See the external-type example.

export interface Position {
  x: double;
  y: double | null;
}

Instead of changing the output to be a type alias, a custom 'literal' type can be set instead.

import kotlinx.serialization.builtins.serializer
import io.github.esafak.kotlintsgen.core.*

@Serializable
data class Item(
  val price: Double,
  val count: Int,
)

fun main() {
  val tsGenerator = KotlinTsGenerator()

  tsGenerator.descriptorOverrides +=
    Double.serializer().descriptor to TsLiteral.Custom("customDouble")

  println(tsGenerator.generate(Item.serializer()))
}

See the custom-literal example.

This produces no type alias, and Double is overridden to be customDouble.

export interface Item {
  price: customDouble;
  count: Int;
}

export type Int = number;

Override nullable properties

Even though UInt is nullable, it should be overridden by the UInt defined in descriptorOverrides.

import kotlinx.serialization.builtins.serializer
import io.github.esafak.kotlintsgen.core.*

@Serializable
data class ItemHolder(
  val item: Item,
)

@Serializable
data class Item(
  val count: UInt? = 0u,
  val score: Int? = 0,
)

fun main() {
  val tsGenerator = KotlinTsGenerator()

  tsGenerator.descriptorOverrides +=
    UInt.serializer().descriptor to TsDeclaration.TsTypeAlias(
      id = TsElementId("kotlin.UInt"),
      typeRef = TsTypeRef.Declaration(id = TsElementId("uint"), parent = null, nullable = false)
    )

  tsGenerator.descriptorOverrides += Int.serializer().descriptor to TsLiteral.Custom("customInt")

  println(tsGenerator.generate(ItemHolder.serializer()))
}

See the nullable-property override example.

export interface ItemHolder {
  item: Item;
}

export interface Item {
  count?: UInt | null;
  score?: customInt | null;
}

export type UInt = uint;

Override both nullable and non-nullable descriptors

Tick has a non-nullable UInt, while Item has a nullable UInt. Also, in ItemHolder, Tick is nullable. Even though a non-nullable override for UInt is supplied, the output shouldn't have conflicting overrides.

import kotlinx.serialization.builtins.serializer
import io.github.esafak.kotlintsgen.core.*


@Serializable
@JvmInline
value class Tick(val value: UInt)

@Serializable
@JvmInline
value class Phase(val value: Int)

@Serializable
data class ItemHolder(
  val item: Item,
  val tick: Tick?,
  val phase: Phase?,
)

@Serializable
data class Item(
  val count: UInt? = 0u,
  val score: Int? = 0,
)

fun main() {
  val tsGenerator = KotlinTsGenerator()

  tsGenerator.descriptorOverrides +=
    UInt.serializer().descriptor to TsDeclaration.TsTypeAlias(
      id = TsElementId("kotlin.UInt"),
      typeRef = TsTypeRef.Declaration(id = TsElementId("uint"), parent = null, nullable = false)
    )

  tsGenerator.descriptorOverrides += Int.serializer().descriptor to TsLiteral.Custom("customInt")

  println(tsGenerator.generate(ItemHolder.serializer()))
}

See the nullable and non-nullable override example.

export interface ItemHolder {
  item: Item;
  tick: Tick | null;
  phase: Phase | null;
}

export interface Item {
  count?: UInt | null;
  score?: customInt | null;
}

export type Tick = UInt;

export type Phase = customInt;

export type UInt = uint;