Proguard + Shadow JAR for non Android Project (Java 11 Swing)

build.gradle.kts

import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
import com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar
import proguard.gradle.ProGuardTask

plugins {
    id("application")
    id("org.jetbrains.kotlin.jvm") version "1.6.0"
    id("com.github.johnrengelman.shadow") version "7.1.0"
}

repositories {
    mavenCentral()
    gradlePluginPortal()
    maven { setUrl("https://jitpack.io") }
}

dependencies {
    implementation(kotlin("stdlib-jdk8"))
    implementation("com.google.code.gson:gson:2.8.9")
    testImplementation("org.junit.jupiter:junit-jupiter:5.7.2")
}

buildscript {
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath("com.guardsquare:proguard-gradle:7.1.1") {
            exclude("com.android.tools.build")
        }
    }
}

application {
    mainClass.set("com.adierebel.MainKt")
    sourceSets["main"].resources {
        srcDir("src/main/res")
    }
    sourceSets["main"].java {
        srcDir("src/main/java")
    }
}

tasks.jar { enabled = false }

artifacts.archives(tasks.shadowJar)

tasks.withType<KotlinCompile> {
    kotlinOptions {
        jvmTarget = "1.8"
    }
}

tasks.withType<ShadowJar> {
    archiveFileName.set("app.jar")
    exclude("DebugProbesKt.bin")
    exclude("META-INF/**")
}

tasks.register<ProGuardTask>("proguardJar") {
    outputs.upToDateWhen { false }
    dependsOn("clean")
    dependsOn("shadowJar")
    configuration("proguard-rules.pro")
}

proguard-rules.pro

-injars  build/libs/app.jar
-outjars build/libs/app-min.jar

-libraryjars <java.home>/jmods/java.base.jmod(!**.jar;!module-info.class)
-libraryjars <java.home>/jmods/java.compiler.jmod(!**.jar;!module-info.class)
-libraryjars <java.home>/jmods/java.datatransfer.jmod(!**.jar;!module-info.class)
-libraryjars <java.home>/jmods/java.desktop.jmod(!**.jar;!module-info.class)
-libraryjars <java.home>/jmods/java.instrument.jmod(!**.jar;!module-info.class)
-libraryjars <java.home>/jmods/java.logging.jmod(!**.jar;!module-info.class)
-libraryjars <java.home>/jmods/java.management.jmod(!**.jar;!module-info.class)
-libraryjars <java.home>/jmods/java.management.rmi.jmod(!**.jar;!module-info.class)
-libraryjars <java.home>/jmods/java.naming.jmod(!**.jar;!module-info.class)
-libraryjars <java.home>/jmods/java.net.http.jmod(!**.jar;!module-info.class)
-libraryjars <java.home>/jmods/java.prefs.jmod(!**.jar;!module-info.class)
-libraryjars <java.home>/jmods/java.rmi.jmod(!**.jar;!module-info.class)
-libraryjars <java.home>/jmods/java.scripting.jmod(!**.jar;!module-info.class)
-libraryjars <java.home>/jmods/java.se.jmod(!**.jar;!module-info.class)
-libraryjars <java.home>/jmods/java.security.jgss.jmod(!**.jar;!module-info.class)
-libraryjars <java.home>/jmods/java.security.sasl.jmod(!**.jar;!module-info.class)
-libraryjars <java.home>/jmods/java.smartcardio.jmod(!**.jar;!module-info.class)
-libraryjars <java.home>/jmods/java.sql.jmod(!**.jar;!module-info.class)
-libraryjars <java.home>/jmods/java.sql.rowset.jmod(!**.jar;!module-info.class)
-libraryjars <java.home>/jmods/java.transaction.xa.jmod(!**.jar;!module-info.class)
-libraryjars <java.home>/jmods/java.xml.crypto.jmod(!**.jar;!module-info.class)
-libraryjars <java.home>/jmods/java.xml.jmod(!**.jar;!module-info.class)

-dontoptimize
-dontshrink

-keep class !com.adierebel.**, !com.adierebel.** { *; }
-keepclasseswithmembers public class com.javafx.main.Main, org.eclipse.jdt.internal.jarinjarloader.*, com.adierebel.MainKt {
    public static void main(java.lang.String[]);
}

-dontwarn okio.**
-dontwarn okhttp3.**
-dontwarn retrofit2.**
-dontwarn org.apache.**
-dontwarn com.sun.**
-dontwarn com.j256.ormlite.**
-dontwarn com.google.protobuf.**
-dontwarn com.google.common.**
-dontwarn com.mysql.**
-dontwarn java.util.**
-dontwarn javax.imageio.**
-dontwarn javax.swing.plaf.**
-dontwarn javax.xml.**
-dontwarn java.sql.**

-ignorewarnings

# GSON
-keepattributes Signature
-keepattributes Signature
-keep class * extends com.google.gson.TypeAdapter
-keep class * implements com.google.gson.TypeAdapterFactory
-keep class * implements com.google.gson.JsonSerializer
-keep class * implements com.google.gson.JsonDeserializer
-keepclassmembers,allowobfuscation class * {
  @com.google.gson.annotations.SerializedName <fields>;
}
-keep,allowobfuscation,allowshrinking class com.google.gson.reflect.TypeToken
-keep,allowobfuscation,allowshrinking class * extends com.google.gson.reflect.TypeToken