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
   

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2. ΛRROW
   Who am I?
   @vergauwen_simon
   

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3. Arrow’s 2.0 Trajectory
   Arrow’s
   history
   Complexity
   of FP
   Evolving
   (OSS) APIs
   Embracing
   Language
   Eco-system
   ΛRROW
   

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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
   

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5. ΛRROW
   Arrow’s History
   Typeclasses &
   Higher Kinded
   Types
   < 0.12.x
   

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6. Complexity of Higher-Kinded Types
   interface GistsApi {
   
   
   fun publicGistsForUser(username: String): Kind>
   >
   
   }
   
   
   interface Logger {
   
   
   fun log(msg: String): Kind
   
   
   }
   ΛRROW
   

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7. Complexity of Higher-Kinded Types
   fun main() {
   
   
   GistsApi(MonoK.async(), MonoKLogger, HttpClient.newHttpClient())
   
   
   .publicGistsForUser("nomisRev")
   
   
   .fix()
   
   
   .mono
   
   
   .block()
   
   
   .let(
   ::
   println)
   
   
   }
   ΛRROW
   

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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
   

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9. Arrow’s History
   Typeclasses &
   Higher Kinded
   Types
   Rehaul of
   Arrow
   < 0.12.x
   0.12.x
   ΛRROW
   

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10. Complexity of FP
    Steep learning curve Non-idiomatic Foreign concepts,
    no language support
    ΛRROW
    

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11. Suspend to the rescue
    interface GistsApi {
    
    
    suspend fun publicGistsForUser(username: String): List
    
    
    }
    
    
    interface Logger {
    
    
    suspend fun log(msg: String): Unit
    
    
    }
    ΛRROW
    

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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
    

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13. Arrow’s History
    Typeclasses &
    Higher Kinded
    Types
    Rehaul of
    Arrow
    < 0.12.x
    0.12.x
    Suspend &
    Kotlin
    Idiomatic
    1.x.x
    ΛRROW
    

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14. Wrapper specific code
    fun GithubUser.process(): Either =
    
    
    if (login.isNotEmpty()) ProcessedUser(this).right()
    
    
    else ProcessingFailed.left()
    ΛRROW
    

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15. Embracing DSLs
    fun GithubUser.process(): Either =
    
    
    either.eager {
    
    
    ensure(login.isNotEmpty()) { ProcessingFailed }
    
    
    ProcessedUser(this@process)
    
    
    }
    ΛRROW
    

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16. Traverse & co
    fun List.processAll(): Either>>
    =
    
    
    traverse(GithubUser
    ::
    process)
    ΛRROW
    

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17. Traverse = map + bind
    fun List.processAll(): Either>>
    =
    
    
    either.eager {
    
    
    map { it.process().bind() }
    
    
    }
    ΛRROW
    

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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
    

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19. DSLs and smart-contracts
    val res: Either = either {
    
    
    val x: Int? = null
    
    
    ensureNotNull(x) { "X was zero" }
    
    
    x + 1
    
    
    }
    ΛRROW
    

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20. Idiomatic API names
    inline fun Either.getOrElse(default: (A)
    ->
    B): B
    

    

    fun Either.getOrNull(): B?
    
    
    inline fun Either.onRight(action: (right: B)
    -
    >
    Unit): Either
    
    
    fun Either.leftOrNull(): A?
    
    
    inline fun Either.onLeft(action: (left: A)
    ->
    Unit): Either
    ΛRROW
    

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21. Context receivers
    context(Raise)
    
    
    fun GithubUser.process(): ProcessedUser {
    
    
    ensure(login.isNotEmpty()) { ProcessingFailed }
    
    
    return ProcessedUser(this)
    
    
    }
    
    
    

    context(Raise)
    
    
    fun List.processAll(): List =
    
    
    map { it.process() }
    ΛRROW
    

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22. DSLs everywhere
    suspend fun ResourceScope.dataSource(): HikariDataSource =
    
    
    closeable { HikariDataSource(HikariConfig()) }
    
    
    suspend fun SagaScope.example(): String =
    
    
    saga({ "Update user" }) { println("Rollback user") }
    ΛRROW
    

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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
    

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24. Evolving APIs
    Community
    feedback
    Iteration makes
    perfect
    Breaking
    
    
    Changes
    ΛRROW
    

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25. IntelliJ
    @Deprecated(
    
    
    RedundantAPI + "Prefer the new recover API",
    
    
    ReplaceWith("recover { a
    ->
    f(a).bind() }", "arrow.core.recover")
    
    
    )
    
    
    inline fun Either.handleErrorWith(f: (A)
    ->
    Either): Either
    ΛRROW
    

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26. IntelliJ ΛRROW
    

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27. OpenRewrite ΛRROW
    

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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
    

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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
    

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30. ΛRROW
    Large-scale automated refactoring
    
    
    Experimental Kotlin Support
    
    
    Support JVM & commonMain
    
    
    Friendly & helpful community
    
    
    First Arrow recipe
    OpenRewrite
    

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31. Documentation ΛRROW
    

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32. Migration Guide ΛRROW
    

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33. Eco System ΛRROW
    

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34. Community ΛRROW
    

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35. Community
    https://slack-chats.kotlinlang.org/c/arrow https://github.com/arrow-kt
    ΛRROW
    

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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
    

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