Gradle Kmp

Gradle for Kotlin Multiplatform

Deep Knowledge: Use mcp__documentation__fetch_docs with technology: gradle-kmp or gradle.

settings.gradle.kts

pluginManagement {
    repositories {
        google { content { includeGroupByRegex("com\\.android.*"); includeGroupByRegex("androidx.*") } }
        mavenCentral()
        gradlePluginPortal()
    }
}

dependencyResolutionManagement {
    repositoriesMode.set(RepositoriesMode.FAIL_ON_PROJECT_REPOS)
    repositories {
        google()
        mavenCentral()
        maven("https://maven.pkg.jetbrains.space/public/p/compose/dev")
        // For UniFFI KMP fork
        maven("https://maven.ubique.ch/snapshots")
    }
}

plugins {
    id("org.gradle.toolchains.foojay-resolver-convention") version "0.8.0"
    id("com.gradle.develocity") version "3.18.1"          // optional: build scan + cache
}

develocity {
    buildScan {
        termsOfUseUrl = "https://gradle.com/terms-of-service"
        termsOfUseAgree = "yes"
        publishing.onlyIf { System.getenv("CI") != null }
    }
}

rootProject.name = "BHODL"
include(":shared")
include(":apps:android")
include(":apps:desktop")

Version Catalog (gradle/libs.versions.toml)

Single source of truth for dependency versions. Replaces ad-hoc ext blocks.

[versions]
kotlin = "2.2.0"
agp = "8.7.0"
compose-multiplatform = "1.8.0"
ktor = "3.0.0"
coroutines = "1.10.0"
serialization = "1.7.3"
sqldelight = "2.0.2"
koin = "4.0.0"

[libraries]
kotlin-bom = { module = "org.jetbrains.kotlin:kotlin-bom", version.ref = "kotlin" }
kotlin-stdlib = { module = "org.jetbrains.kotlin:kotlin-stdlib", version.ref = "kotlin" }
coroutines-core = { module = "org.jetbrains.kotlinx:kotlinx-coroutines-core", version.ref = "coroutines" }
coroutines-test = { module = "org.jetbrains.kotlinx:kotlinx-coroutines-test", version.ref = "coroutines" }
serialization-json = { module = "org.jetbrains.kotlinx:kotlinx-serialization-json", version.ref = "serialization" }
ktor-core = { module = "io.ktor:ktor-client-core", version.ref = "ktor" }
ktor-content-negotiation = { module = "io.ktor:ktor-client-content-negotiation", version.ref = "ktor" }
ktor-serialization = { module = "io.ktor:ktor-serialization-kotlinx-json", version.ref = "ktor" }
ktor-okhttp = { module = "io.ktor:ktor-client-okhttp", version.ref = "ktor" }
ktor-darwin = { module = "io.ktor:ktor-client-darwin", version.ref = "ktor" }
sqldelight-runtime = { module = "app.cash.sqldelight:runtime", version.ref = "sqldelight" }
sqldelight-android = { module = "app.cash.sqldelight:android-driver", version.ref = "sqldelight" }
sqldelight-native = { module = "app.cash.sqldelight:native-driver", version.ref = "sqldelight" }
koin-core = { module = "io.insert-koin:koin-core", version.ref = "koin" }

[bundles]
ktor-common = ["ktor-core", "ktor-content-negotiation", "ktor-serialization"]

[plugins]
kotlin-multiplatform = { id = "org.jetbrains.kotlin.multiplatform", version.ref = "kotlin" }
kotlin-android = { id = "org.jetbrains.kotlin.android", version.ref = "kotlin" }
kotlin-compose = { id = "org.jetbrains.kotlin.plugin.compose", version.ref = "kotlin" }
kotlin-serialization = { id = "org.jetbrains.kotlin.plugin.serialization", version.ref = "kotlin" }
android-application = { id = "com.android.application", version.ref = "agp" }
android-library = { id = "com.android.library", version.ref = "agp" }
compose = { id = "org.jetbrains.compose", version.ref = "compose-multiplatform" }
sqldelight = { id = "app.cash.sqldelight", version.ref = "sqldelight" }

Use:

plugins {
    alias(libs.plugins.kotlin.multiplatform)
}

dependencies {
    implementation(libs.coroutines.core)
    implementation(libs.bundles.ktor.common)
}

gradle.properties

# JVM
org.gradle.jvmargs=-Xmx4g -XX:+UseG1GC -XX:MaxMetaspaceSize=1g

# Performance
org.gradle.parallel=true
org.gradle.caching=true
org.gradle.configureondemand=true
org.gradle.configuration-cache=true                # Gradle 8+ stable
org.gradle.unsafe.configuration-cache-problems=warn

# Kotlin
kotlin.code.style=official
kotlin.mpp.androidSourceSetLayoutVersion=2
kotlin.mpp.enableCInteropCommonization=true
kotlin.native.cacheKind=static                      # Faster Native build
kotlin.native.ignoreDisabledTargets=true            # Skip iOS targets on Linux

# Android
android.useAndroidX=true
android.nonTransitiveRClass=true
android.nonFinalResIds=true

# Compose
org.jetbrains.compose.experimental.uikit.enabled=true

Source Set Hierarchy

KMP 1.9+ has a default template — most projects don't need custom intermediate sets.

kotlin {
    androidTarget()
    jvm("desktop")
    listOf(iosX64(), iosArm64(), iosSimulatorArm64()).forEach { /* ... */ }

    sourceSets {
        commonMain.dependencies {
            implementation(libs.coroutines.core)
        }
        androidMain.dependencies {
            implementation(libs.ktor.okhttp)
        }
        iosMain.dependencies {
            implementation(libs.ktor.darwin)
        }
        commonTest.dependencies {
            implementation(kotlin("test"))
            implementation(libs.coroutines.test)
        }
    }
}

For custom intermediate set (e.g., shared between Android + Desktop):

sourceSets {
    val jvmCommonMain by creating {
        dependsOn(commonMain.get())
    }
    androidMain.get().dependsOn(jvmCommonMain)
    getByName("desktopMain").dependsOn(jvmCommonMain)
}

XCFramework Output

import org.jetbrains.kotlin.gradle.plugin.mpp.apple.XCFramework

kotlin {
    val xcf = XCFramework("Shared")
    listOf(iosX64(), iosArm64(), iosSimulatorArm64()).forEach { target ->
        target.binaries.framework {
            baseName = "Shared"
            isStatic = true
            xcf.add(this)
            export(libs.coroutines.core.get())          // expose to Swift consumers
        }
    }
}

Build:

./gradlew :shared:assembleSharedXCFramework
# Output: shared/build/XCFrameworks/release/Shared.xcframework

CocoaPods Plugin

plugins {
    kotlin("native.cocoapods") version "2.2.0"
}

kotlin {
    cocoapods {
        version = "1.0.0"
        summary = "Shared KMP module"
        homepage = "https://github.com/example/bhodl"
        ios.deploymentTarget = "16.0"
        framework {
            baseName = "Shared"
            isStatic = true
        }
        // Optionally consume CocoaPods deps from Kotlin
        pod("FirebaseAuth") { version = "11.0.0" }
    }
}

./gradlew :shared:podPublishXCFramework
cd apps/ios && pod install

Embed-and-Sign for Xcode

Auto-build framework when Xcode builds:

# In Xcode build phase:
cd "$SRCROOT/.."
./gradlew :shared:embedAndSignAppleFrameworkForXcode

The embedAndSignAppleFrameworkForXcode task is auto-registered by KMP plugin.

Kotlin Compiler Options

kotlin {
    targets.all {
        compilations.all {
            compilerOptions.configure {
                freeCompilerArgs.addAll(
                    "-Xexpect-actual-classes",
                    "-Xcontext-parameters",
                    "-opt-in=kotlin.RequiresOptIn",
                    "-opt-in=kotlinx.coroutines.ExperimentalCoroutinesApi",
                    "-Xjsr305=strict",
                )
            }
        }
    }
    androidTarget {
        compilerOptions {
            jvmTarget.set(JvmTarget.JVM_17)
        }
    }
    jvm("desktop") {
        compilerOptions {
            jvmTarget.set(JvmTarget.JVM_17)
        }
    }
}

Maven Publishing

plugins {
    `maven-publish`
    signing
}

group = "com.bhodl"
version = "1.0.0"

publishing {
    repositories {
        maven {
            name = "GitHubPackages"
            url = uri("https://maven.pkg.github.com/bhodl/shared")
            credentials {
                username = providers.gradleProperty("gpr.user").orNull
                    ?: System.getenv("GITHUB_ACTOR")
                password = providers.gradleProperty("gpr.token").orNull
                    ?: System.getenv("GITHUB_TOKEN")
            }
        }
        maven {
            name = "MavenCentral"
            url = uri("https://s01.oss.sonatype.org/service/local/staging/deploy/maven2/")
            credentials {
                username = providers.gradleProperty("ossrhUsername").orNull
                password = providers.gradleProperty("ossrhPassword").orNull
            }
        }
    }
    publications.withType<MavenPublication> {
        pom {
            name.set("Shared")
            description.set("Shared KMP module")
            url.set("https://github.com/bhodl/shared")
            licenses {
                license {
                    name.set("MIT")
                    url.set("https://opensource.org/licenses/MIT")
                }
            }
            developers {
                developer { id.set("bhodl"); name.set("BHODL Team") }
            }
            scm {
                url.set("https://github.com/bhodl/shared")
            }
        }
    }
}

signing {
    val signingKey = providers.environmentVariable("SIGNING_KEY").orNull
    val signingPassword = providers.environmentVariable("SIGNING_PASSWORD").orNull
    if (signingKey != null) {
        useInMemoryPgpKeys(signingKey, signingPassword)
        sign(publishing.publications)
    }
}

For modern Maven Central → use vanniktech/gradle-maven-publish-plugin:

plugins {
    id("com.vanniktech.maven.publish") version "0.30.0"
}

mavenPublishing {
    publishToMavenCentral(SonatypeHost.CENTRAL_PORTAL)
    signAllPublications()
    coordinates("com.bhodl", "shared", "1.0.0")
    pom { /* ... */ }
}

Build Cache

Local cache

# gradle.properties
org.gradle.caching=true

Stored in ~/.gradle/caches/build-cache-1.

Remote cache (CI / team)

// settings.gradle.kts
buildCache {
    local { enabled = true }
    remote<HttpBuildCache> {
        url = uri("https://cache.bhodl.dev/cache/")
        push = System.getenv("CI") != null               // only CI pushes
        credentials {
            username = providers.gradleProperty("buildCacheUser").orNull
            password = providers.gradleProperty("buildCachePass").orNull
        }
    }
}

Or use Gradle Develocity (formerly Gradle Enterprise) — best-in-class with build scans.

Configuration Cache (Gradle 8+)

# gradle.properties
org.gradle.configuration-cache=true
org.gradle.unsafe.configuration-cache-problems=warn

Caches build configuration → faster subsequent builds (skip configuration phase).

If a plugin doesn't support it, set =warn and gradually fix incompatible code (no Project.afterEvaluate, no Task.project, etc.).

Composite Builds

For monorepos splitting independent modules:

// settings.gradle.kts
includeBuild("../bhodl-core") {
    dependencySubstitution {
        substitute(module("com.bhodl:core")).using(project(":"))
    }
}

Build of root project automatically builds and uses local bhodl-core. No publish needed.

Common Gradle Tasks

# Build everything
./gradlew build

# Just one target
./gradlew :shared:assembleDebug                  # Android library debug
./gradlew :shared:linkReleaseFrameworkIosArm64   # iOS device framework
./gradlew :shared:assembleSharedXCFramework      # All iOS arch into XCFramework
./gradlew :shared:desktopJar
./gradlew :apps:android:assembleRelease
./gradlew :apps:android:bundleRelease            # AAB for Play Store
./gradlew :apps:android:installDebug             # Install on connected device

# Tests
./gradlew test                                   # JVM tests
./gradlew :shared:jvmTest
./gradlew :shared:iosSimulatorArm64Test
./gradlew :shared:desktopTest

# Quality
./gradlew :shared:detekt
./gradlew :shared:ktlintCheck
./gradlew :shared:lintDebug                      # Android lint

# Publishing
./gradlew :shared:publishToMavenLocal
./gradlew :shared:publishAllPublicationsToMavenCentralRepository

# Cleanup
./gradlew clean
./gradlew --refresh-dependencies                 # force re-resolve

# Diagnostics
./gradlew :shared:dependencies
./gradlew :shared:dependencyInsight --dependency kotlinx-coroutines-core
./gradlew :shared:tasks --all
./gradlew help --task assembleDebug              # docs for a task

# Performance
./gradlew --scan                                 # build scan to scans.gradle.com
./gradlew --profile                              # local HTML profile in build/reports/profile/
./gradlew --build-cache                          # force cache use

CI: GitHub Actions

# .github/workflows/build.yml
name: Build

on:
  push:
    branches: [main]
  pull_request:

concurrency:
  group: ${{ github.workflow }}-${{ github.ref }}
  cancel-in-progress: true

jobs:
  build:
    strategy:
      fail-fast: false
      matrix:
        os: [ubuntu-latest, macos-14]
    runs-on: ${{ matrix.os }}
    steps:
      - uses: actions/checkout@v4

      - uses: actions/setup-java@v4
        with: { java-version: '17', distribution: 'temurin' }

      - name: Setup Gradle
        uses: gradle/actions/setup-gradle@v4
        with:
          cache-read-only: ${{ github.ref != 'refs/heads/main' }}

      - name: Build (Linux: skip iOS targets)
        if: runner.os == 'Linux'
        run: ./gradlew assembleDebug -Pkotlin.native.ignoreDisabledTargets=true

      - name: Build full (macOS: includes iOS)
        if: runner.os == 'macOS'
        run: ./gradlew assemble

      - name: Test
        run: ./gradlew test

      - name: Upload reports
        if: failure()
        uses: actions/upload-artifact@v4
        with:
          name: reports-${{ matrix.os }}
          path: |
            **/build/reports/
            **/build/test-results/

Caching tips for CI

• Use gradle/actions/setup-gradle@v4 — handles Gradle home + dependency cache automatically
• cache-read-only on PRs to avoid polluting cache from forks
• For Konan (Native), cache ~/.konan separately

CI: GitLab CI Snippet

build:
  image: eclipse-temurin:17-jdk
  cache:
    paths:
      - .gradle/
      - ~/.gradle/caches/
  script:
    - ./gradlew assembleDebug --build-cache --parallel
    - ./gradlew test
  artifacts:
    when: on_failure
    paths:
      - "**/build/reports/"

Anti-Patterns

Convention Plugins (build-logic/)

For monorepos with many modules sharing config:

build-logic/
├── settings.gradle.kts
├── convention/
│   ├── build.gradle.kts
│   └── src/main/kotlin/
│       ├── bhodl.kotlin-multiplatform.gradle.kts
│       ├── bhodl.android-application.gradle.kts
│       └── bhodl.android-library.gradle.kts

// bhodl.kotlin-multiplatform.gradle.kts
plugins {
    kotlin("multiplatform")
}

kotlin {
    targets.all {
        compilations.all {
            compilerOptions.configure {
                freeCompilerArgs.addAll("-Xexpect-actual-classes", "-Xcontext-parameters")
            }
        }
    }
}

// In a module
plugins {
    id("bhodl.kotlin-multiplatform")
}

Troubleshooting

When NOT to Use This Skill