Seskar

Seskar is a gradle plugin that provides useful additions for Kotlin/JS projects.

Setup

To add Seskar to your project, you need to the following configuration to your project's build.gradle.kts:

plugins {
    kotlin("js") version "1.7.20"
    id("io.github.turansky.seskar") version "0.17.0"
}

// browser target
dependencies {
    implementation("io.github.turansky.seskar:seskar-core:0.17.0")
}

React

Props

Seskar checks if interfaces that inherit from the Props interface are external.

Dependencies [IR]

When a project uses the Kotlin/JS IR compiler, value classes are autoboxed. If a value class is used as a dependency of a react hook (e.g., in useMemo, useState or useEffect), a new class will be created on every rendering pass, which causes infinite re-rendering.

To prevent this, Seskar provides a @JsValue marker, which disables autoboxing for value class dependencies in hooks. Also, it converts Long values to String.

Seskar supports Duration by default, so no @JsValue marker is needed.

@JsValue - example

import seskar.js.JsValue

@JsValue
value class Count(
    private val value: Int,
)

val Counter = VFC {
    val count: Count = useCount()
    
    useEffect(count) {
        println("Count changed: $count")
    }
}

Without plugin

function Counter() { 
    var count = useCount()
    
    useEffect(
        () => {
            println(`Count changed: $count`)
        },
        // AUTOBOXING
        [ new Count(count) ],
    )
}

With plugin

function Counter() { 
    var count = useCount()
    
    useEffect(
        () => {
            println(`Count changed: $count`)
        },
        // NO AUTOBOXING
        [ count ],
    )
}

Unions [IR]

AS-IS

Use enum constant as union value

// TypeScript
type Align = 'TOP' | 'LEFT' | 'BOTTOM' | 'RIGHT'

// Kotlin
import seskar.js.JsUnion

@JsUnion
external enum class Align {
    TOP,
    LEFT,
    BOTTOM,
    RIGHT,

    ;
}

println(Align.TOP)  // 'TOP'
println(Align.LEFT) // 'LEFT'

Kebab case

// TypeScript
type LayoutOrientation = 'top-to-bottom' 
    | 'left-to-right'
    | 'bottom-to-top'
    | 'right-to-left'

// Kotlin
import seskar.js.JsUnion
import seskar.js.Case

@JsUnion(case = Case.KEBAB)
external enum class LayoutOrientation {
    TOP_TO_BOTTOM, // 'top-to-bottom'
    LEFT_TO_RIGHT, // 'left-to-right'
    bottomToTop,   // 'bottom-to-top'
    rightToLeft,   // 'right-to-left'

    ;
}

Snake case

// TypeScript
type LayoutOrientation = 'top_to_bottom' 
    | 'left_to_right'
    | 'bottom_to_top'
    | 'right_to_left'

// Kotlin
import seskar.js.JsUnion
import seskar.js.Case

@JsUnion(case = Case.SNAKE)
external enum class LayoutOrientation {
    TOP_TO_BOTTOM, // 'top_to_bottom'
    LEFT_TO_RIGHT, // 'left_to_right'
    bottomToTop,   // 'bottom_to_top'
    rightToLeft,   // 'right_to_left'

    ;
}

Custom

Use String or Int constant as union value

String

// TypeScript
type Align = 't' | 'l' | 'b' | 'r'

// Kotlin
import seskar.js.JsUnion
import seskar.js.JsValue

@JsUnion
external enum class CustomAlign {
    @JsString("t")
    TOP,

    @JsString("l")
    LEFT,

    @JsString("b")
    BOTTOM,

    @JsString("r")
    RIGHT,

    ;
}

println(CustomAlign.TOP)  // 't'
println(CustomAlign.LEFT) // 'l'

Int

// TypeScript
type GRAPH_ITEM_TYPE_NODE = 1
type GRAPH_ITEM_TYPE_EDGE = 2
type GRAPH_ITEM_TYPE_PORT = 3
type GRAPH_ITEM_TYPE_LABEL = 4

type GraphItemType = GRAPH_ITEM_TYPE_NODE
    | GRAPH_ITEM_TYPE_EDGE
    | GRAPH_ITEM_TYPE_PORT
    | GRAPH_ITEM_TYPE_LABEL

// Kotlin
import seskar.js.JsInt
import seskar.js.JsValue

@JsUnion
external enum class GraphItemType {
    @JsInt(1)
    NODE,

    @JsInt(2)
    EDGE,

    @JsInt(4)
    PORT,

    @JsInt(8)
    LABEL,

    ;
}

println(GraphItemType.EDGE) // 2
println(GraphItemType.PORT) // 4

How it works?

TBD