Added kotlin support and docs

[Daniel1464]

Adds a "kotlin support" page within the docs that provides a kotlin replacement for the AutoLog annotation. Resolves #64 and #86.

Note: this probably should be merged after the 2025-docs-dev branch is merged.

[reecelikesramen]

I was able to get Kotlin to work with the annotations and minimal changes with KAPT and this build.gradle:

plugins {
    id "java"
    id "edu.wpi.first.GradleRIO" version "2025.1.1"
    id "com.diffplug.spotless" version "7.0.1" // formatting
    id "org.jetbrains.kotlin.jvm" version "2.1.10" // kotlin support
    id "com.peterabeles.gversion" version "1.10" // for advantagekit
    // id "com.google.devtools.ksp" version "2.1.10-1.0.31" // for annotation processing
    id "org.jetbrains.kotlin.kapt" version "2.1.10"
}

java {
    sourceCompatibility = JavaVersion.VERSION_17
    targetCompatibility = JavaVersion.VERSION_17
}

def ROBOT_MAIN_CLASS = "com.eaganrobotics.frc.Main"

// Define my targets (RoboRIO) and artifacts (deployable files)
// This is added by GradleRIO"s backing project DeployUtils.
deploy {
    targets {
        roborio(getTargetTypeClass("RoboRIO")) {
            // Team number is loaded either from the .wpilib/wpilib_preferences.json
            // or from command line. If not found an exception will be thrown.
            // You can use getTeamOrDefault(team) instead of getTeamNumber if you
            // want to store a team number in this file.
            team = project.frc.getTeamNumber()
            debug = project.frc.getDebugOrDefault(false)

            artifacts {
                // First part is artifact name, 2nd is artifact type
                // getTargetTypeClass is a shortcut to get the class type using a string

                frcJava(getArtifactTypeClass("FRCJavaArtifact")) {
                    jvmArgs.add("-XX:+UnlockExperimentalVMOptions")
                    jvmArgs.add("-XX:GCTimeRatio=5")
                    jvmArgs.add("-XX:+UseSerialGC")
                    jvmArgs.add("-XX:MaxGCPauseMillis=50")

                    final MAX_JAVA_HEAP_SIZE_MB = 100;
                    jvmArgs.add("-Xmx" + MAX_JAVA_HEAP_SIZE_MB + "M")
                    jvmArgs.add("-Xms" + MAX_JAVA_HEAP_SIZE_MB + "M")
                    jvmArgs.add("-XX:+AlwaysPreTouch")
                }

                // Static files artifact
                frcStaticFileDeploy(getArtifactTypeClass("FileTreeArtifact")) {
                    files = project.fileTree("src/main/deploy")
                    directory = "/home/lvuser/deploy"
                    deleteOldFiles = true
                }
            }
        }
    }
}

def deployArtifact = deploy.targets.roborio.artifacts.frcJava

// Set to true to use debug for JNI.
wpi.java.debugJni = false

// Set this to true to enable desktop support.
def includeDesktopSupport = true

// Defining my dependencies. In this case, WPILib (+ friends), and vendor libraries.
// Also defines JUnit 5.
dependencies {
    annotationProcessor wpi.java.deps.wpilibAnnotations()
    implementation wpi.java.deps.wpilib()
    implementation wpi.java.vendor.java()

    roborioDebug wpi.java.deps.wpilibJniDebug(wpi.platforms.roborio)
    roborioDebug wpi.java.vendor.jniDebug(wpi.platforms.roborio)

    roborioRelease wpi.java.deps.wpilibJniRelease(wpi.platforms.roborio)
    roborioRelease wpi.java.vendor.jniRelease(wpi.platforms.roborio)

    nativeDebug wpi.java.deps.wpilibJniDebug(wpi.platforms.desktop)
    nativeDebug wpi.java.vendor.jniDebug(wpi.platforms.desktop)
    simulationDebug wpi.sim.enableDebug()

    nativeRelease wpi.java.deps.wpilibJniRelease(wpi.platforms.desktop)
    nativeRelease wpi.java.vendor.jniRelease(wpi.platforms.desktop)
    simulationRelease wpi.sim.enableRelease()

    testImplementation "org.junit.jupiter:junit-jupiter:5.10.1"
    testRuntimeOnly "org.junit.platform:junit-platform-launcher"

    implementation "org.jetbrains.kotlin:kotlin-reflect"
    implementation "org.jetbrains.kotlin:kotlin-stdlib"

    // advantagekit
    def akitJson = new groovy.json.JsonSlurper().parseText(new File(projectDir.getAbsolutePath() + "/vendordeps/AdvantageKit.json").text)
    // implementation "org.littletonrobotics.akit:akit-autolog:$akitJson.version"
    kapt "org.littletonrobotics.akit:akit-autolog:$akitJson.version"
}

test {
    useJUnitPlatform()
    systemProperty "junit.jupiter.extensions.autodetection.enabled", "true"
}

// Simulation configuration (e.g. environment variables).
wpi.sim.addGui().defaultEnabled = providers.environmentVariable("AKIT_SIM_MODE").map(env -> env.equals("SIM")).orElse(true)
wpi.sim.addDriverstation()

// Setting up my Jar File. In this case, adding all libraries into the main jar ("fat jar")
// in order to make them all available at runtime. Also adding the manifest so WPILib
// knows where to look for our Robot Class.
jar {
    from { configurations.runtimeClasspath.collect { it.isDirectory() ? it : zipTree(it) } }
    from sourceSets.main.allSource
    manifest edu.wpi.first.gradlerio.GradleRIOPlugin.javaManifest(ROBOT_MAIN_CLASS)
    duplicatesStrategy = DuplicatesStrategy.INCLUDE
}

// Configure jar and deploy tasks
deployArtifact.jarTask = jar
wpi.java.configureExecutableTasks(jar)
wpi.java.configureTestTasks(test)

// Configure string concat to always inline compile
tasks.withType(JavaCompile) {
    options.compilerArgs.add "-XDstringConcat=inline"
}

// advantagekit replay watch
task(replayWatch, type: JavaExec) {
    mainClass = "org.littletonrobotics.junction.ReplayWatch"
    classpath = sourceSets.main.runtimeClasspath
}

// version control for advantagekit for event autodeploy
project.compileJava.dependsOn(createVersionFile)
gversion {
  srcDir       = "src/main/kotlin/"
  classPackage = "com.eaganrobotics.frc"
  className    = "BuildConstants"
  dateFormat   = "yyyy-MM-dd HH:mm:ss z"
  timeZone     = "America/Central" // Use preferred time zone
  indent       = "  "
  language     = "kotlin"
}

// event auto commit when working in branches prefixed with "event/"
task(eventDeploy) {
    doLast {
        if (project.gradle.startParameter.taskNames.any({ it.toLowerCase().contains("deploy") })) {
            def branchPrefix = "event/"
            def branch = "git branch --show-current".execute().text.trim()
            def commitMessage = "Update at "${new Date().toString()}""

            if (branch.startsWith(branchPrefix)) {
                exec {
                    workingDir(projectDir)
                    executable "git"
                    args "add", "-A"
                }
                exec {
                    workingDir(projectDir)
                    executable "git"
                    args "commit", "-m", commitMessage
                    ignoreExitValue = true
                }

                println "Committed to branch: "$branch""
                println "Commit message: "$commitMessage""
            } else {
                println "Not on an event branch, skipping commit"
            }
        } else {
            println "Not running deploy task, skipping commit"
        }
    }
}
createVersionFile.dependsOn(eventDeploy)

// formatting task
spotless {
  java {
    googleJavaFormat()
    formatJavadoc(true)
    reorderImports(true)
    targetExclude("**/build/**", "**/build-*/**", "src/main/java/frc/robot/BuildConstants.java")
    removeUnusedImports()
    trimTrailingWhitespace()
    endWithNewline()
    licenseHeader("// Copyright (c) 2025 FRC 2220\n// http://github.com/EaganRobotics\n//\n// Use of this source code is governed by an MIT-style\n// license that can be found in the LICENSE file at\n// the root directory of this project.\n\n")
    manageTrailingCommas(true)
  }
  kotlin {
    // version, style and all configurations here are optional
    ktfmt("0.54") {
      googleStyle()
      formatJavadoc(true)
      reorderImports(true)
      targetExclude("**/build/**", "**/build-*/**", "src/main/kotlin/com/eaganarobotics/frc/BuildConstants.kt")
      removeUnusedImports()
      trimTrailingWhitespace()
      endWithNewline()
      licenseHeader("// Copyright (c) 2025 FRC 2220\n// http://github.com/EaganRobotics\n//\n// Use of this source code is governed by an MIT-style\n// license that can be found in the LICENSE file at\n// the root directory of this project.\n\n")
      manageTrailingCommas(true)
    }
  }
  groovyGradle {
      target fileTree(".") {
          include "**/*.gradle"
          exclude "**/build/**", "**/build-*/**", "northstar/**"
      }
      greclipse()
      indentWithSpaces(4)
      trimTrailingWhitespace()
      endWithNewline()
  }
  json {
      target fileTree(".") {
          include "**/*.json"
          exclude "**/build/**", "**/build-*/**", "northstar/**"
      }
      gson().indentWithSpaces(2)
  }
  enforceCheck = false
}

and here's an IO class example:

interface LiftIO {

  companion object {
    @AutoLog
    open class LiftIOInputs {
      @JvmField var lowerLimit = false
      @JvmField var winchPosition = Radians.of(0.0)
      @JvmField var winchVelocity = RadiansPerSecond.of(0.0)
      @JvmField var winchAppliedVoltage = Volts.of(0.0)
      @JvmField var winchCurrent = Amps.of(0.0)
    }
  }

  fun updateInputs(inputs: LiftIOInputs): Unit {}

  fun setWinchOpenLoop(output: Voltage): Unit {}

  fun setWinchClosedLoop(position: Angle): Unit {}

  fun zeroWinchEncoder(): Unit {}
}

Just @ me if there are any questions! We're switching to kotlin for next season and AKit support was a hard stop for us.

[Daniel1464]

Yeah I was aware of the workaround where u use kapt and @JvmField your properties. I don't like it as much though because typing out @JvmField for everything feels annoying(and might not be intuitive for new teams) but it would be supported better.

Second thing: your inputs class shouldn't be in a companion object. Classes defined directly within other classes are static by default, so you can do this:

interface LiftIO {
   @AutoLog
   open class LiftIOInputs {
      @JvmField var lowerLimit = false
      @JvmField var winchPosition = Radians.of(0.0)
      @JvmField var winchVelocity = RadiansPerSecond.of(0.0)
      @JvmField var winchAppliedVoltage = Volts.of(0.0)
      @JvmField var winchCurrent = Amps.of(0.0)
   }

  fun updateInputs(inputs: LiftIOInputs) {}

  fun setWinchOpenLoop(output: Voltage) {}

  fun setWinchClosedLoop(position: Angle) {}

  fun zeroWinchEncoder() {}
}

(you also don't need the Unit return type since its basically 'void' in java, and it is returned by default if you dont specify a return type).
I personally prefer the style where the lift inputs and lift io are separate classes defined within the same file, so

@AutoLog
open class LiftIOInputs {
  @JvmField var lowerLimit = false
  @JvmField var winchPosition = Radians.of(0.0)
  @JvmField var winchVelocity = RadiansPerSecond.of(0.0)
  @JvmField var winchAppliedVoltage = Volts.of(0.0)
  @JvmField var winchCurrent = Amps.of(0.0)
}

interface LiftIO {
  fun updateInputs(inputs: LiftIOInputs) {}

  fun setWinchOpenLoop(output: Voltage) {}

  fun setWinchClosedLoop(position: Angle) {}

  fun zeroWinchEncoder() {}
}

[katzuv]

Thank you for the work on that; it has been helpful to us.
I was wondering if there's a way to enable @AutoLogOutput for variables created in files outside classes?