[Bug] Building Android App Bundle fails with error Unknown Kotlin JVM target: 21

[sunderee]

Bug description

This bug occurs when I attempt to build an Android App Bundle.

FAILURE: Build failed with an exception.

* What went wrong:
Could not determine the dependencies of task ':klippa_identity_verification_sdk:compileReleaseKotlin'.
> Unknown Kotlin JVM target: 21

* Try:
> Run with --stacktrace option to get the stack trace.
> Run with --info or --debug option to get more log output.
> Run with --scan to get full insights.
> Get more help at https://help.gradle.org.

BUILD FAILED in 1s

flutter doctor output below:

Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 3.24.3, on macOS 15.0.1 24A348 darwin-arm64, locale
    en-US)
[✓] Android toolchain - develop for Android devices (Android SDK version 35.0.0)
[✓] Xcode - develop for iOS and macOS (Xcode 16.0)
[✓] Chrome - develop for the web
[✓] Android Studio (version 2024.2)
[✓] VS Code (version 1.94.2)
[✓] Connected device (3 available)
[✓] Network resources

• No issues found!

Possible solutions

One of the possible solutions I've found on Stack Overflow would be to declare source compatibility like so:

compileOptions {
    sourceCompatibility = JavaVersion.VERSION_1_8
    targetCompatibility = JavaVersion.VERSION_1_8
}

kotlinOptions {
    jvmTarget = JavaVersion.VERSION_1_8
}

It might also be useful to look into similar issues faced by official Flutter packages (example: video_player).

[sunderee]

Update: was able to resolve build issues after modifying package's build.gradle file:

group 'com.klippa.identity_verification.klippa_identity_verification_sdk'
version '1.0-SNAPSHOT'

buildscript {
    ext.kotlin_version = '1.7.21'
    repositories {
        google()
        mavenCentral()
    }

    dependencies {
        classpath 'com.android.tools.build:gradle:7.3.1'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
    }
}

def keystoreProperties = new Properties()
def keystorePropertiesFile = rootProject.file('key.properties')
if (keystorePropertiesFile.exists()) {
    keystoreProperties.load(new FileInputStream(keystorePropertiesFile))
}

rootProject.allprojects {
    repositories {
        google()
        mavenCentral()
        maven { url "https://jitpack.io" }
        maven {
            credentials {
                username System.getenv()['KLIPPA_IDENTITY_VERIFICATION_SDK_USERNAME'] ? System.getenv()['KLIPPA_IDENTITY_VERIFICATION_SDK_USERNAME'] : (keystoreProperties["klippa.identity_verification.sdk.username"] ? keystoreProperties["klippa.identity_verification.sdk.username"] : '')
                password System.getenv()['KLIPPA_IDENTITY_VERIFICATION_SDK_PASSWORD'] ? System.getenv()['KLIPPA_IDENTITY_VERIFICATION_SDK_PASSWORD'] : (keystoreProperties["klippa.identity_verification.sdk.password"] ? keystoreProperties["klippa.identity_verification.sdk.password"] : '')
            }
            url System.getenv()['KLIPPA_IDENTITY_VERIFICATION_SDK_URL'] ? System.getenv()['KLIPPA_IDENTITY_VERIFICATION_SDK_URL'] : (keystoreProperties["klippa.identity_verification.sdk.url"] ? keystoreProperties["klippa.identity_verification.sdk.url"] : 'https://custom-ocr.klippa.com/sdk/android/maven')
        }
    }
}

apply plugin: 'com.android.library'
apply plugin: 'kotlin-android'

android {
    compileSdkVersion 35
    
    sourceSets {
        main.java.srcDirs += 'src/main/kotlin'
    }

    defaultConfig {
        minSdkVersion 24
    }

    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }

    kotlinOptions {
        jvmTarget = '1.8'
    }

    lintOptions {
        disable 'InvalidPackage'
    }
}

dependencies {
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
    def klippaIdentityVerificationVersion = project.hasProperty('klippaIdentityVerificationVersion') ? project.klippaIdentityVerificationVersion : "0.7.5"
    implementation "com.klippa:identity_verification:$klippaIdentityVerificationVersion"
}

I don't think that upgrading compileSdkVersion from 33 to 35 is necessary.

---

I do not think that this is related to your package, but I additionally had to make this particular change in my android/build.gradle, and also modify the ndkVersion in android/app/build.gradle to 25.1.8937393.