KotlinConf - Arrow's 2.0 Trajectory

Since the first commit 10 years ago Arrow has travelled a long path to reach 2.0, this talk will take us through the journey, decisions, and challenges that shaped Arrow.

Arrow aims to bring functional programming patterns to Kotlin in an idiomatic way, by leveraging Kotlin's DSL features to represent complex programs in elegant ways.

Transcript

1. @vergauwen_simon KotlinConf’23 Amsterdam Arrow’s 2.0 Trajectory Simon Vergauwen Xebia Functional
2. ΛRROW Who am I? @vergauwen_simon
3. Arrow’s 2.0 Trajectory Arrow’s history Complexity of FP Evolving (OSS) APIs Embracing Language Eco-system ΛRROW
4. Arrow’s History Oct 2017 March 2017 FineCinnamon/Katz Dec 2017 arrow-kt June 2017 Kategory March 2013 MarioAriasC/funKTionale Sept 2017 nomisRev/optikal ΛRROW
5. ΛRROW Arrow’s History Typeclasses & Higher Kinded Types < 0.12.x
6. Complexity of Higher-Kinded Types interface GistsApi<F> { fun publicGistsForUser(username: String): Kind<F, ListK<Gist > > } interface Logger<F> { fun log(msg: String): Kind<F, Unit> } ΛRROW
7. Complexity of Higher-Kinded Types fun main() { GistsApi(MonoK.async(), MonoKLogger, HttpClient.newHttpClient()) .publicGistsForUser("nomisRev") .fix() .mono .block() .let( :: println) } ΛRROW
8. Complexity of Higher-Kinded Types fun main() { GistsApi(IO.async(), ... ) // Arrow Fx IO GistsApi(DeferredK.async(), ... ) // KotlinX Coroutines Deferred GistsApi(SingleK.async(), ... ) // RxJava Single } ΛRROW
9. Arrow’s History Typeclasses & Higher Kinded Types Rehaul of Arrow < 0.12.x 0.12.x ΛRROW
10. Complexity of FP Steep learning curve Non-idiomatic Foreign concepts, no language support ΛRROW
11. Suspend to the rescue interface GistsApi { suspend fun publicGistsForUser(username: String): List<Gist> } interface Logger { suspend fun log(msg: String): Unit } ΛRROW
12. Suspend to the rescue fun main() { val api = GistApi(Logger.Default, HttpClient.newHttpClient()) runBlocking { api.publicGistsForUser("nomisRev") } mono { api.publicGistsForUser("raulraja") } scope.future { api.publicGistsForUser("serras") } 
 // ... } ΛRROW
13. Arrow’s History Typeclasses & Higher Kinded Types Rehaul of Arrow < 0.12.x 0.12.x Suspend & Kotlin Idiomatic 1.x.x ΛRROW
14. Wrapper specific code fun GithubUser.process(): Either<ProcessingFailed, ProcessedUser> = if (login.isNotEmpty()) ProcessedUser(this).right() else ProcessingFailed.left() ΛRROW
15. Embracing DSLs fun GithubUser.process(): Either<ProcessingFailed, ProcessedUser> = either.eager { ensure(login.isNotEmpty()) { ProcessingFailed } ProcessedUser(this@process) } ΛRROW
16. Traverse & co fun List<GithubUser>.processAll(): Either<ProcessingFailed, List<ProcessedUser >> = traverse(GithubUser :: process) ΛRROW
17. Traverse = map + bind fun List<GithubUser>.processAll(): Either<ProcessingFailed, List<ProcessedUser >> = either.eager { map { it.process().bind() } } ΛRROW
18. Arrow’s History Typeclasses & Higher Kinded Types Rehaul of Arrow < 0.12.x 0.12.x Suspend & Kotlin Idiomatic Small Uniform APIs & learning curve 1.x.x 2.x.x ΛRROW
19. DSLs and smart-contracts val res: Either<String, Int> = either { val x: Int? = null ensureNotNull(x) { "X was zero" } x + 1 } ΛRROW
20. Idiomatic API names inline fun Either<A, B>.getOrElse(default: (A) -> B): B 
 
 fun Either<A, B>.getOrNull(): B? inline fun Either<A, B>.onRight(action: (right: B) - > Unit): Either<A, B> fun Either<A, B>.leftOrNull(): A? inline fun Either<A, B>.onLeft(action: (left: A) -> Unit): Either<A, B> ΛRROW
21. Context receivers context(Raise<ProcessingFailed>) fun GithubUser.process(): ProcessedUser { ensure(login.isNotEmpty()) { ProcessingFailed } return ProcessedUser(this) } 
 context(Raise<ProcessingFailed>) fun List<GithubUser>.processAll(): List<ProcessedUser> = map { it.process() } ΛRROW
22. DSLs everywhere suspend fun ResourceScope.dataSource(): HikariDataSource = closeable { HikariDataSource(HikariConfig()) } suspend fun SagaScope.example(): String = saga({ "Update user" }) { println("Rollback user") } ΛRROW
23. Binary Size Arrow 0.11.0 Arrow 1.0.0 Arrow 2.0.0 5000 4000 3000 2000 1000 0 ΛRROW 4,1 MB 3,1 MB 429 KB
24. Evolving APIs Community feedback Iteration makes perfect Breaking Changes ΛRROW
25. IntelliJ @Deprecated( RedundantAPI + "Prefer the new recover API", ReplaceWith("recover { a -> f(a).bind() }", "arrow.core.recover") ) inline fun <A, B, C> Either<A, B>.handleErrorWith(f: (A) -> Either<C, B>): Either<C, B> ΛRROW
26. IntelliJ ΛRROW
27. OpenRewrite ΛRROW
28. OpenRewrite plugins { kotlin("jvm") id("org.openrewrite.rewrite") version "5.39.3" } dependencies { rewrite(“io.arrow-kt:rewrite-arrow:1.0.0-RC3“) } rewrite { activeRecipe("arrow.RaiseRefactor") } ΛRROW
29. OpenRewrite ./gradlew :sample:rewriteRun > Task :sample:rewriteRun Validating active recipes Parsing sources from project sample All sources parsed, running active recipes: arrow.RaiseRefactor Changes have been made to sample/src/main/kotlin/org/example/example.kt by: arrow.RaiseRefactor org.openrewrite.java.ChangeMethodName: .. . org.openrewrite.java.ChangeType: . .. Please review and commit the results. ΛRROW
30. ΛRROW Large-scale automated refactoring Experimental Kotlin Support Support JVM & commonMain Friendly & helpful community First Arrow recipe OpenRewrite
31. Documentation ΛRROW
32. Migration Guide ΛRROW
33. Eco System ΛRROW
34. Community ΛRROW
35. Community https://slack-chats.kotlinlang.org/c/arrow https://github.com/arrow-kt ΛRROW
36. Visit us at the booth to talk to Arrow contributors & Xebia Functional and get discount on courses.
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37. Thank you,
 and don’t forget
 to vote @vergauwen_simon KotlinConf’23 Amsterdam