Add packagingResourcesRootDir to expose jpackage --resource-dir

jpackage's --resource-dir is the documented override mechanism for
packaging resources (DMG volume icon via <name>-volume.icns, DMG
background, Linux preinst/postinst scripts, WiX templates, ...), but
Compose fully owns that directory: AbstractJPackageTask clears it and
repopulates it with the generated Info.plist on every run, so users
have no supported way to contribute their own files to it.

Add a packagingResourcesRootDir DSL property, mirroring appResourcesRootDir
(with common/<os>/<os>-<arch> subdirectories). Its files are copied into
the jpackage resource dir after it is cleared but before the generated
Info.plist/product-def.plist are written, so the Compose-managed plists
always take precedence over user-supplied files.

This revives the approach a maintainer suggested on JetBrains#1843 and supersedes
the abandoned JetBrains#3647. Unlike JetBrains#1843 -- which repointed jpackageResources at
a Sync output and so had its files removed by clearDirs -- the files are
copied in after the clear, so nothing is wiped. Addresses CMP-2042,
CMP-6411, CMP-1972, CMP-9837.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: CloudyDino

gradle-plugins/compose/src/main/kotlin/org/jetbrains/compose/desktop/application/dsl/AbstractDistributions.kt

@@ -30,6 +30,20 @@ abstract class AbstractDistributions {
     var description: String? = null
     var vendor: String? = null
     val appResourcesRootDir: DirectoryProperty = objects.directoryProperty()
+
+    /**
+     * Root directory for files passed to the underlying packaging tool (jpackage)
+     * via `--resource-dir`, used to override the tool's own packaging resources (e.g.
+     * a `<package-name>-volume.icns` DMG volume icon, a DMG background, Linux
+     * `preinst`/`postinst` scripts, or WiX templates). See
+     * https://docs.oracle.com/en/java/javase/21/jpackage/override-jpackage-resources.html
+     *
+     * Files are resolved from `common`, `<os>` and `<os>-<arch>` subdirectories, the
+     * same layout as [appResourcesRootDir]. The generated `Info.plist` and
+     * `product-def.plist` are managed by Compose and always take precedence.
+     */
+    val packagingResourcesRootDir: DirectoryProperty = objects.directoryProperty()
+
     val licenseFile: RegularFileProperty = objects.fileProperty()
 
     var targetFormats: Set<TargetFormat> = EnumSet.noneOf(TargetFormat::class.java)

gradle-plugins/compose/src/main/kotlin/org/jetbrains/compose/desktop/application/internal/configureJvmApplication.kt

@@ -318,6 +318,7 @@ private fun JvmApplicationContext.configurePackageTask(
         packageTask.packageVendor.set(packageTask.provider { executables.vendor })
         packageTask.packageVersion.set(packageVersionFor(packageTask.targetFormat))
         packageTask.licenseFile.set(executables.licenseFile)
+        packageTask.packagingResourcesRootDir.set(executables.packagingResourcesRootDir)
     }
 
     packageTask.destinationDir.set(app.nativeDistributions.outputBaseDir.map {

gradle-plugins/compose/src/main/kotlin/org/jetbrains/compose/desktop/application/tasks/AbstractJPackageTask.kt

@@ -377,6 +377,11 @@ abstract class AbstractJPackageTask @Inject constructor(
     @get:Internal
     val appResourcesDir: DirectoryProperty = objects.directoryProperty()
 
+    @get:InputDirectory
+    @get:Optional
+    @get:PathSensitive(PathSensitivity.RELATIVE)
+    val packagingResourcesRootDir: DirectoryProperty = objects.directoryProperty()
+
     @get:Internal
     private val libsMappingFile: Provider<RegularFile> = workingDir.map {
         it.file("libs-mapping.txt")
@@ -607,6 +612,7 @@ abstract class AbstractJPackageTask @Inject constructor(
         }
 
         fileOperations.clearDirs(jpackageResources)
+        copyUserPackagingResources()
         if (currentOS == OS.MacOS) {
             InfoPlistBuilder(macExtraPlistKeysRawXml.orNull)
                 .also { setInfoPlistValues(it) }
@@ -626,6 +632,33 @@ abstract class AbstractJPackageTask @Inject constructor(
         }
     }
 
+    /**
+     * Copies user-supplied packaging override resources into [jpackageResources]
+     * (the `--resource-dir` passed to jpackage). Files are taken from the `common`,
+     * `<os>` and `<os>-<arch>` subdirectories of [packagingResourcesRootDir], mirroring
+     * the layout of `appResourcesRootDir`. Called after [jpackageResources] is cleared
+     * but before the generated `Info.plist`/`product-def.plist` are written, so those
+     * Compose-managed files always win over anything the user drops in.
+     */
+    private fun copyUserPackagingResources() {
+        val rootDir = packagingResourcesRootDir.ioFileOrNull ?: return
+        val destDir = jpackageResources.ioFile
+        for (subDirName in listOf("common", currentOS.id, currentTarget.id)) {
+            val sourceDir = rootDir.resolve(subDirName)
+            if (!sourceDir.isDirectory) continue
+            for (file in sourceDir.walk()) {
+                val relPath = file.relativeTo(sourceDir).path
+                if (relPath.isEmpty()) continue
+                val destFile = destDir.resolve(relPath)
+                if (file.isDirectory) {
+                    fileOperations.mkdirs(destFile)
+                } else {
+                    file.copyTo(destFile, overwrite = true)
+                }
+            }
+        }
+    }
+
     override fun jvmToolEnvironment(): MutableMap<String, String> =
         super.jvmToolEnvironment().apply {
             if (currentOS == OS.Windows) {

gradle-plugins/compose/src/test/kotlin/org/jetbrains/compose/test/tests/integration/DesktopApplicationTest.kt

@@ -593,6 +593,19 @@ class DesktopApplicationTest : GradlePluginTestBase() {
         }
     }
 
+    @Test
+    fun packagingResources() = with(testProject("application/packagingResources")) {
+        gradle(":createDistributable").checks {
+            check.taskSuccessful(":createDistributable")
+
+            // Files from packagingResourcesRootDir must be copied into the
+            // directory passed to jpackage via --resource-dir, for both the
+            // `common` and the current-OS subdirectories.
+            file("build/compose/tmp/resources/common-packaging-resource.txt").checkExists()
+            file("build/compose/tmp/resources/os-specific-packaging-resource.txt").checkExists()
+        }
+    }
+
     @Test
     fun testWixUnzip() {
         Assumptions.assumeTrue(currentOS == OS.Windows) { "The test is only relevant for Windows" }

gradle-plugins/compose/src/test/test-projects/application/packagingResources/build.gradle

@@ -0,0 +1,24 @@
+import org.jetbrains.compose.desktop.application.dsl.TargetFormat
+
+plugins {
+    id "org.jetbrains.kotlin.jvm"
+    id "org.jetbrains.kotlin.plugin.compose"
+    id "org.jetbrains.compose"
+}
+
+dependencies {
+    implementation "org.jetbrains.kotlin:kotlin-stdlib"
+    implementation compose.desktop.currentOs
+}
+
+compose.desktop {
+    application {
+        mainClass = "MainKt"
+        nativeDistributions {
+            targetFormats(TargetFormat.Dmg, TargetFormat.Msi, TargetFormat.Deb)
+            packageVersion = "1.0.0"
+
+            packagingResourcesRootDir.set(project.layout.projectDirectory.dir("packaging-resources"))
+        }
+    }
+}

gradle-plugins/compose/src/test/test-projects/application/packagingResources/packaging-resources/common/common-packaging-resource.txt

@@ -0,0 +1 @@
+common packaging resource

gradle-plugins/compose/src/test/test-projects/application/packagingResources/packaging-resources/linux/os-specific-packaging-resource.txt

@@ -0,0 +1 @@
+linux only packaging resource

gradle-plugins/compose/src/test/test-projects/application/packagingResources/packaging-resources/macos/os-specific-packaging-resource.txt

@@ -0,0 +1 @@
+macos only packaging resource

gradle-plugins/compose/src/test/test-projects/application/packagingResources/packaging-resources/windows/os-specific-packaging-resource.txt

@@ -0,0 +1 @@
+windows only packaging resource

gradle-plugins/compose/src/test/test-projects/application/packagingResources/settings.gradle

@@ -0,0 +1,27 @@
+pluginManagement {
+    plugins {
+        id 'org.jetbrains.kotlin.jvm' version 'KOTLIN_VERSION_PLACEHOLDER'
+        id 'org.jetbrains.kotlin.plugin.compose' version 'KOTLIN_VERSION_PLACEHOLDER'
+        id 'org.jetbrains.compose' version 'COMPOSE_GRADLE_PLUGIN_VERSION_PLACEHOLDER'
+    }
+    repositories {
+        mavenLocal()
+        gradlePluginPortal()
+        mavenCentral()
+        google()
+        maven {
+            url 'https://packages.jetbrains.team/maven/p/cmp/dev'
+        }
+    }
+}
+dependencyResolutionManagement {
+    repositories {
+        mavenCentral()
+        google()
+        maven {
+            url 'https://packages.jetbrains.team/maven/p/cmp/dev'
+        }
+        mavenLocal()
+    }
+}
+rootProject.name = "packagingResources"