java - Kotlin fails to compile a library

There's this library I created to report exceptions via email. It works well with the Android Java project but fails with Android Kotlin. When I add the compile script for the libary (compile 'com.theah64.bugmailer:bugmailer:1.1.9') and tries to build the APK, am getting below error.

Error:Execution failed for task ':app:transformDexArchiveWithExternalLibsDexMergerForDebug'.
> com.android.builder.dexing.DexArchiveMergerException: Unable to merge dex

This is my app's build.gradle file

apply plugin: 'com.android.application'

apply plugin: 'kotlin-android'


apply plugin: 'kotlin-android-extensions'

android {
    compileSdkVersion 27
    defaultConfig {
        applicationId "com.theapache64.calculator"
        minSdkVersion 15
        targetSdkVersion 27
        versionCode 1

        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        multiDexEnabled true
    }
    buildTypes {
        release {
            minifyEnabled false
            multiDexEnabled true
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }

    }
    dexOptions {
        preDexLibraries = false
        javaMaxHeapSize "4g"
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation"org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"

    implementation 'com.android.support:appcompat-v7:27.0.2'
    implementation 'com.android.support.constraint:constraint-layout:1.0.2'
    implementation 'com.android.support:design:27.0.2'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.1'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.1'
    compile 'com.theah64.bugmailer:bugmailer:1.2.0'
}

I've googled a lot and tried the multiDexEnabled solution. but it doesn't work.

Answer

The problem you are having is caused by conflicting dependencies, 2 of your dependencies are defining the same classes. If you try to compile with

./gradlew --stacktrace app:assembleDebug

You would see this error

Caused by: com.android.dex.DexException: Multiple dex files define Lorg/intellij/lang/annotations/MagicConstant;

Now, you can analyze all the dependency trees with

./gradlew app:dependencies

And see these (simplified here):

+--- com.theah64.bugmailer:bugmailer:1.2.0
|    +--- org.jetbrains:annotations-java5:15.0

and

 +--- org.jetbrains.kotlin:kotlin-stdlib:1.2.30
 |    \--- org.jetbrains:annotations:13.0

So, both Kotlin std lib and bugmailer are using org.jetbrains annotation, but from 2 different modules. This causes a problem because the same class (MagicConstant in that case) is being defined twice, I think that the duplicate entries would be even more.

The solution would be to exclude one of the 2 transitive dependencies, for instance

compile('com.theah64.bugmailer:bugmailer:1.2.0') {
    exclude group: 'org.jetbrains', module: 'annotations-java5'
}

You will be able to compile the app, but, keep in mind that this solution is based on the assumption that bugmailer will work just fine with org.jetbrains:annotations:13.0 instead of org.jetbrains:annotations-java5:15.0