izhangzhihao / unmeta

remove all Kotlin Metadata and DebugMetadata annotations from .class files

Unmeta Kotlin gradle plugin 🐘

A Gradle plugin to remove all Kotlin @Metadata / @DebugMetadata / @SourceDebugExtension annotations from the compile output and jars.

Kotlin @Metadata and @DebugMetadata annotations are not fully processed by ProGuard / R8 and contain un-obfuscated symbol information, both in binary and plain text forms. This information can be used to more easily reverse engineer your code.

This plugin allows removing all Kotlin @Metadata / @DebugMetadata / @SourceDebugExtension annotations from generated class files. This is safe to do as long as:

• you do not intend to use the resulting binaries as a Kotlin library (@Metadata annotations are used to determine Kotlin function definitions),
• you are not using Kotlin Reflection (certain reflection functionality depends on the presence of the @Metadata annotations).

By using the Kotlin dsl in build.gradle.kt

plugins {
    kotlin("jvm")
    id("io.github.izhangzhihao.unmeta") version "1.0.2"
}

unmeta {
    enable.set(true)
}

To enable the plugin only for release builds add this section:

gradle.taskGraph.whenReady {
    if (allTasks.any { it.name.contains("release") }) {
        unmeta {
            enable.set(true)
        }
    } else {
        unmeta {
            enable.set(false)
        }
    }
}

By using the Groovy dsl in build.gradle

plugins {
    id 'org.jetbrains.kotlin.jvm' version '1.8.21'
    id "io.github.izhangzhihao.unmeta" version "1.0.2"
}

unmeta {
    enable.set(true)
}

To enable the plugin only for release builds add this section:

gradle.taskGraph.whenReady { graph ->
    if (graph.getAllTasks().any { it.name.contains("release") }) {
        unmeta {
            enable.set(true)
        }
    } else {
        unmeta {
            enable.set(false)
        }
    }
}

Verify

./gradlew clean jar --dry-run
:clean SKIPPED
:compileKotlin SKIPPED
:unmeta SKIPPED
:compileJava SKIPPED
:processResources SKIPPED
:classes SKIPPED
:jar SKIPPED

You might need this to force the unmeta task runs before the jar task:

jar {
    mustRunAfter("unmeta")
}

Dependency substitution

Please note that the project relies on module name/group in order for dependency substitution to work properly. If you change only the plugin ID everything will work as expected. If you change module name/group, things might break and you probably have to specify a substitution rule.

Contributing 🤝

Feel free to open a issue or submit a pull request for any bugs/improvements.

./gradlew --project-dir plugin-build publishToMavenLocal

License 📄

This template is licensed under the MIT License - see the License file for details.

unmeta's Issues

Task with name 'compileKotlin' not found in project ':app'.

An exception occurred applying plugin request [id: 'io.github.izhangzhihao.unmeta', version: '1.0.0']

Failed to apply plugin 'io.github.izhangzhihao.unmeta'.
Task with name 'compileKotlin' not found in project ':app'.

How to configure it in Build.gradle Groovy

Kindly add Build.gradle Groovy documentation