Add r8Jar task to minify fatJar using R8

gradle/libs.versions.toml

@@ -32,3 +32,4 @@ junit5 = "org.junit.jupiter:junit-jupiter:5.10.1"
 assertj = "org.assertj:assertj-core:3.24.2"
 sarif4k = "io.github.detekt.sarif4k:sarif4k:0.5.0"
 jimfs = "com.google.jimfs:jimfs:1.3.0"
+r8 = "com.android.tools:r8:8.1.56"

ktlint-cli/build.gradle.kts

@@ -8,6 +8,8 @@ plugins {
     signing
 }
 
+val r8: Configuration by configurations.creating
+
 tasks.jar {
     manifest {
         attributes("Main-Class" to "com.pinterest.ktlint.Main")
@@ -37,29 +39,59 @@ dependencies {
     runtimeOnly(projects.ktlintCliReporterSarif)
 
     testImplementation(projects.ktlintTest)
+
+    r8(libs.r8)
+}
+
+val r8File =
+    layout
+        .buildDirectory
+        .file("libs/ktlint-cli-$version-r8.jar")
+        .get()
+        .asFile
+val rulesFile = file("src/main/proguard.pro")
+val fatJarFile = tasks.shadowJar.get().archiveFile
+val r8Jar by tasks.registering(JavaExec::class) {
+    description = "Creates a jar minified from the fat jar using R8"
+    group = "Distribution"
+    dependsOn(tasks.shadowJar)
+
+    // Find the "ktlint-cli-<version>-all.jar" file
+    val fatJar =
+        tasks
+            .shadowJar
+            .get()
+            .outputs
+            .files
+            .singleFile
+    inputs.file(fatJar)
+    inputs.file(rulesFile)
+    outputs.file(r8File)
+
+    classpath = r8
+    mainClass = "com.android.tools.r8.R8"
+    args =
+        listOf(
+            "--release",
+            "--classfile",
+            "--output", r8File.toString(),
+            "--pg-conf", rulesFile.path,
+            "--lib", System.getProperty("java.home").toString(),
+            fatJarFile.get().toString(),
+        )
 }
 
 // Implements https://github.com/brianm/really-executable-jars-maven-plugin maven plugin behaviour.
 // To check details how it works, see https://skife.org/java/unix/2011/06/20/really_executable_jars.html.
 val shadowJarExecutable by tasks.registering(DefaultTask::class) {
     description = "Creates self-executable file, that runs generated shadow jar"
     group = "Distribution"
-
-    dependsOn(tasks.shadowJar)
+    dependsOn(r8Jar)
 
     val isReleaseBuild = !version.toString().endsWith("SNAPSHOT")
 
-    // Find the "ktlint-cli-<version>-all.jar" file
-    val ktlintCliAllJarFile =
-        tasks
-            .shadowJar
-            .orNull
-            ?.outputs
-            ?.files
-            ?.singleFile
-            ?: throw GradleException("Can not locate the jar file for building the self-executable ktlint-cli")
-    logger.lifecycle("ktlint-cli: Base jar to build self-executable file: ${ktlintCliAllJarFile.absolutePath}")
-    inputs.files(ktlintCliAllJarFile)
+    logger.lifecycle("ktlint-cli: Base jar to build self-executable file: ${r8File.absolutePath}")
+    inputs.files(r8File)
 
     val windowsBatchFileInputPath = "$projectDir/src/main/scripts/ktlint.bat"
     inputs.files(windowsBatchFileInputPath)
@@ -100,7 +132,7 @@ val shadowJarExecutable by tasks.registering(DefaultTask::class) {
                 """.trimIndent(),
             )
             // Add the jar
-            appendBytes(ktlintCliAllJarFile.readBytes())
+            appendBytes(r8File.readBytes())
 
             setExecutable(true, false)
 

ktlint-cli/src/main/proguard.pro

@@ -0,0 +1,17 @@
+-dontobfuscate
+-keepattributes SourceFile, LineNumberTable
+
+-allowaccessmodification
+
+-keep class com.pinterest.ktlint.Main {
+  public static void main(java.lang.String[]);
+}
+
+-dontwarn com.sun.jna.Native.**
+-dontwarn javax.servlet.ServletContainerInitializer
+-dontwarn kotlin.annotations.jvm.**
+-dontwarn kotlinx.coroutines.**
+-dontwarn org.checkerframework.checker.nullness.qual.**
+-dontwarn org.codehaus.janino.ClassBodyEvaluator
+-dontwarn org.jetbrains.annotations.**
+-dontwarn org.jetbrains.kotlin.com.google.**

settings.gradle.kts

@@ -11,6 +11,7 @@ dependencyResolutionManagement {
     repositoriesMode = RepositoriesMode.FAIL_ON_PROJECT_REPOS
     repositories {
         mavenCentral()
+        google()
     }
 }