How to Publish Your First Kotlin Multiplatform Library

Publishing a Kotlin multiplatform library can be very challenging. This presentation will walk through the whole process from drafting a concept to the publication of your first multiplatform library.

We will be using KStore - a minimal multiplatform library to store objects to disk - as a case study for this presentation. We will explore how it was originally inspired, the original goals and how its API evolved over time to support multiple platforms.

A key goal of this side-project was to make it self-managed as much as possible with minimal overhead so that the open-source community can extend or maintain the library even in my absence. To achieve this I've incorporated a number of tools to upkeep standards from code contributions - tools such as Klover code coverage and binary-compatibility-validator. I've also used a number of automation tools to streamline the process of publishing a multiplatform library - tools such as GitHub actions build matrices to build and test on multiple platforms.

Transcript

1. @IsuruKusumal KotlinConf’23 Amsterdam How to Publish Your First Multiplatform Library
 Isuru Rajapakse Android Developer, Motorola Solutions
2. Introduction https: // github.com/xxfast/KStore
3. Introduction > Lifecycle of a library
4. Lifecycle Incubate Develop Publish Maintain Introduction > Lifecycle of a library
5. @v1 @v2 @v3 Introduction > Lifecycle of a library
6. Top 10 Essential Tools YOU NEED! to Publish Your Own Multiplatform Library! Introduction
7. Develop Lifecycle of a library Incubate
8. 1. In ation cub spir Incubate > Inspire
9. Incubate > Inspire
10. interface ValueStore<T> { fun get(): Maybe<T> fun observePut(value: T): Single<T> fun observe(): Observable<ValueUpdate<T>?> fun observeClear(): Completable class ValueUpdate<T>(val value: T?) } RxStore Incubate > Inspire
11. class KStore<T : @Serializable Any> { suspend fun get(): T? suspend fun put(value: T) val updates: Flow<T?> suspend fun clear() } KStore Incubate > Inspire
12. ate ncub sol 2. I Incubate > Isolate
13. Incubate > Isolate YourProject YourLibrary
14. YourProject YourLibrary commonMain kotlin au.com.myproject screens feature-1 feature-2 utils MyLibrary Incubate > Isolate
15. @RequiresOptIn(message = "This API is experimental”) @Retention(BINARY) @Target(CLASS, FUNCTION,PROPERTY) annotation class ExperimentalMyLibraryApi feature-1 feature-2 utils MyLibrary YourProject YourLibrary Incubate > Isolate https: // github.com/Kotlin/api-guidelines ExperimentalMyLibraryApi
16. @ExperimentalMyLibraryApi fun interface NewApi { fun doSomethingNew() = TODO() } feature-1 feature-2 utils MyLibrary YourProject YourLibrary Incubate > Isolate https: // github.com/Kotlin/api-guidelines ExperimentalMyLibraryApi @OptIn(ExperimentalMyLibraryApi :: class) val myApi = NewApi { . . }
17. Develop Lifecycle of a library Incubate
18. Lifecycle of a library Develop
19. 3. Setup CI Early! Develop > Continuous Integration
20. Github Actions Develop > Continuous Integration
21. name: Build on: .. jobs: check: .. build: .. release: if: ${{ github.event_name != 'pull_request' }} needs: build publish: if: ${{ github.event_name != 'pull_request' }} needs: build check release publish build Develop > Continuous Integration
22. build name: Build on: .. jobs: check: .. build: strategy: matrix: config: [ { target: android, os: ubuntu-latest, .. }, { target: apple, os: macos-latest, .. }, { target: windows, os: windows-latest, .. } { target: linux, os: ubuntu-latest, .. }, { target: js, os: ubuntu-latest, .. }, { target: desktop, os: ubuntu-latest, .. }, ] runs-on: ${{ matrix.config.os }} check release publish ▾ Matrix: build Build android Build apple Build desktop Build js Build linux Develop > Continuous Integration
23. build name: Build on: .. jobs: check: .. build: strategy: matrix: config: [ { os: ubuntu-latest, tasks: testReleaseUnitTest .. }, { os: macos-latest, tasks: appleTest, .. }, { os: windows-latest, tasks: windowsTest, .. } { os: ubuntu-latest, tasks: linuxTest, .. }, { os: ubuntu-latest, tasks: jsTest .. }, { os: ubuntu-latest, tasks: desktopTest, .. }, ] runs-on: ${{ matrix.config.os }} check release publish ▾ Matrix: build Build android Build apple Build desktop Build js Build linux Develop > Test
24. 4. Declare Public API! Develop > Public API
25. YourLibrary Public API 🤏 Develop > Public API
26. YourLibrary explicitApi() @SinceKotlin("1.4.0") explicitApi() Public API Develop > Public API
27. YourLibrary interface NewApi { fun doSomethingNew() = TODO() } Public API Develop > Public API
28. YourLibrary Public API public interface NewApi { public fun doSomethingNew(): Nothing = TODO() } Develop > Public API
29. 5. Don’t break Compatibility! Develop > Compatibility
30. Develop > Compatibility 1.0.1 2.1.2 1.1.0 2.0.0 YourProject YourLibrary +minor/patch +major 2.1.3 +minor/patch https: // semver.org/
31. kotlinlang.org/docs/jvm-api-guidelines-backward-compatibility.html Develop > Compat . . “Backward-compatible code allows clients of newer API versions to use the same API code that they used with an older API version.”
32. Develop > Compatibility https: / / github.com/Kotlin/binary-compatibility-validator
33. Develop > Compatibility
34. Develop > Compatibility
35. Develop > Compatibility build check ▾ Matrix: build Build android Build apple Build desktop Build js Build linux name: Build on: .. jobs: check: steps: - name: Check api run: ./gradlew apiCheck release publish
36. Develop > Compatibility
37. Publish Lifecycle of a library Develop
38. Lifecycle of a library Publish
39. 6. Document everything! Publish / Documentation
40. plugins { kotlin("multiplatform") id("org.jetbrains.dokka") version "1.8.10" } Publish > Documentation https: // github.com/Kotlin/dokka
41. Publish > Documentation
42. name: Build jobs: publish: if: ${{ github.event_name != 'pull_request' }} steps: - name: Generate docs with dokka run: ./gradlew dokkaHtml - name: Upload artifact uses: actions/upload-pages-artifact@v1 with: path: ${{ github.workspace }}/kstore/build/dokka/html - name: Deploy to GitHub Pages id: deployment uses: actions/deploy-pages@v1 check release publish build Publish > Documentation ▾ Matrix: build
43. 7. Release the Kraken! Publish / Release
44. Publish / Release repositories { mavenCentral() } /** Warning ⚠ Incoming lots of configuration! * 1. Setup and link your OSSRH repository * 2. Include sources + documentation * 3. Sign your artefacts * */ https: // kotlinlang.org/docs/multiplatform-publish-lib.html
45. publishing { repositories { maven { val isSnapshot = version.toString().endsWith("SNAPSHOT") val destination = if (!isSnapshot) "https: // s01.oss.sonatype.org/service/local/stagi else "https: // s01.oss.sonatype.org/content/repositories/snapshots" url = uri(destination) credentials { username = gradleLocalProperties(rootDir).getProperty("sonatypeUse password = gradleLocalProperties(rootDir).getProperty("sonatypePas } plugins { id("maven-publish") id("signing") } Publish / Release https: // central.sonatype.org/publish/publish-guide/ // 1. Link OSSRH repository
46. credentials { username = gradleLocalProperties(rootDir).getProperty("sonatypeUse password = gradleLocalProperties(rootDir).getProperty("sonatypePas } } } publishing { val javadocJar = tasks.register<Jar>("javadocJar") { dependsOn(tasks.dokkaHtml) archiveClassifier.set("javadoc") from("$buildDir/dokka") } publications { withType<MavenPublication> { artifact(javadocJar) pom { name.set("KStore") description.set("A tiny Kotlin multiplatform library that assists licenses { Publish / Release https: // central.sonatype.org/publish/publish-guide/ // 2. Include sources + documentation
47. signing { useInMemoryPgpKeys( gradleLocalProperties(rootDir).getProperty("gpgKeySecret"), gradleLocalProperties(rootDir).getProperty("gpgKeyPassword"), ) sign(publishing.publications) } Publish / Release https: // central.sonatype.org/publish/publish-guide/ // 3. Sign your artefacts
48. Publish / Release https: // central.sonatype.org/publish/publish-guide/
49. release: if: ${{ github.event_name != 'pull_request' }} runs-on: macos-latest needs: - build steps: - name: Write secrets to local.properties if: ${{ github.event_name != 'pull_request' }} run: | echo sonatypeUsername="${SONATYPE_USERNAME}" >> "local. echo sonatypePassword="${SONATYPE_PASSWORD}" >> "local. echo gpgKeyPassword="${GPG_KEY_PASSWORD}" >> "local.pro echo gpgKeySecret="${GPG_KEY_SECRET}" >> "local.propert env: SONATYPE_USERNAME: ${{ secrets.SONATYPE_USERNAME }} SONATYPE_PASSWORD: ${{ secrets.SONATYPE_PASSWORD }} GPG_KEY_PASSWORD: ${{ secrets.GPG_KEY_PASSWORD }} GPG_KEY_SECRET: ${{ secrets.GPG_KEY_SECRET }} - name: Release to sonatype run: ./gradlew publishAllPublicationsToMavenRepository check release publish build Publish / Release ▾ Matrix: build
50. Publish / Release
51. Maintain Lifecycle of a library Publish
52. Lifecycle of a library Maintain
53. 8. Coverage w/ Kover Maintain / Code Coverage
55. Maintain > Code Coverage https: // github.com/Kotlin/kotlinx-kover
56. Maintain > Code Coverage plugins { kotlin("multiplatform") id("org.jetbrains.kotlinx.kover") version "0.6.1" }
57. name: Build jobs: check: steps: - name: Generate kover coverage report run: ./gradlew koverXmlReport - name: Add coverage report to PR if: ${{ github.event_name == 'pull_request' }} id: kover uses: mi-kas/kover-report@v1 with: path: ${{ github.workspace }}/kstore/build/reports/kover/x token: ${{ secrets.GITHUB_TOKEN }} title: Code Coverage update-comment: true min-coverage-overall: 80 min-coverage-changed-files: 80 check release publish build Maintain > Code Coverage ▾ Matrix: build https: // github.com/mi-kas/kover-report
58. Maintain > Code Coverage
59. 9. Let the bots do the bumps! Maintain / Dependency Management
60. Maintain > Dependency Mgmt .. https: // docs.gradle.org/current/userguide/platforms.html
61. Maintain > Dependency Management
62. https: // github.com/joreilly/Confetti Maintain > Dependency Management
63. Maintain > ? 10. Have fun with(kotlin)!
64. Thank you,
 and don’t forget
 to vote @IsuruKusumal KotlinConf’23 Amsterdam