Generate Res class if there is no common composeResource dir (#4176)

gradle-plugins/compose/src/main/kotlin/org/jetbrains/compose/resources/GenerateResClassTask.kt

@@ -16,21 +16,17 @@ abstract class GenerateResClassTask : DefaultTask() {
     @get:Input
     abstract val packageName: Property<String>
 
-    @get:InputDirectory
+    @get:InputFiles
     @get:PathSensitive(PathSensitivity.RELATIVE)
-    abstract val resDir: DirectoryProperty
+    abstract val resDir: Property<File>
 
     @get:OutputDirectory
     abstract val codeDir: DirectoryProperty
 
-    init {
-        this.onlyIf { resDir.asFile.get().exists() }
-    }
-
     @TaskAction
     fun generate() {
         try {
-            val rootResDir = resDir.get().asFile
+            val rootResDir = resDir.get()
             logger.info("Generate resources for $rootResDir")
 
             //get first level dirs

gradle-plugins/compose/src/main/kotlin/org/jetbrains/compose/resources/ResourcesGenerator.kt

@@ -44,8 +44,6 @@ private fun Project.configureResourceGenerator(commonComposeResourcesDir: File,
 
     fun buildDir(path: String) = layout.dir(layout.buildDirectory.map { File(it.asFile, path) })
 
-    val resDir = layout.dir(commonComposeResources)
-
     //lazy check a dependency on the Resources library
     val shouldGenerateResourceAccessors: Provider<Boolean> = provider {
         if (ComposeProperties.alwaysGenerateResourceAccessors(providers).get()) {
@@ -65,7 +63,7 @@ private fun Project.configureResourceGenerator(commonComposeResourcesDir: File,
         GenerateResClassTask::class.java
     ) {
         it.packageName.set(packageName)
-        it.resDir.set(resDir)
+        it.resDir.set(commonComposeResources)
         it.codeDir.set(buildDir("$RES_GEN_DIR/kotlin"))
         it.onlyIf { shouldGenerateResourceAccessors.get() }
     }

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

@@ -116,4 +116,14 @@ class ResourcesTest : GradlePluginTestBase() {
             check.taskSuccessful(":copyFontsToAndroidAssets")
         }
     }
+
+    @Test
+    fun testEmptyResClass(): Unit = with(testProject("misc/emptyResources")) {
+        gradle("generateComposeResClass").checks {
+            assertEqualTextFiles(
+                file("build/generated/compose/resourceGenerator/kotlin/app/group/empty_res/generated/resources/Res.kt"),
+                file("expected/Res.kt")
+            )
+        }
+    }
 }

gradle-plugins/compose/src/test/test-projects/misc/emptyResources/build.gradle.kts

@@ -0,0 +1,20 @@
+plugins {
+    kotlin("multiplatform")
+    id("org.jetbrains.compose")
+}
+
+group = "app.group"
+
+kotlin {
+    jvm("desktop")
+
+    sourceSets {
+        commonMain {
+            dependencies {
+                implementation(compose.runtime)
+                implementation(compose.material)
+                implementation(compose.components.resources)
+            }
+        }
+    }
+}

gradle-plugins/compose/src/test/test-projects/misc/emptyResources/expected/Res.kt

@@ -0,0 +1,21 @@
+package app.group.empty_res.generated.resources
+
+import kotlin.ByteArray
+import kotlin.OptIn
+import kotlin.String
+import org.jetbrains.compose.resources.ExperimentalResourceApi
+import org.jetbrains.compose.resources.readResourceBytes
+
+@OptIn(org.jetbrains.compose.resources.InternalResourceApi::class)
+@ExperimentalResourceApi
+internal object Res {
+    /**
+     * Reads the content of the resource file at the specified path and returns it as a byte array.
+     *
+     * Example: `val bytes = Res.readBytes("files/key.bin")`
+     *
+     * @param path The path of the file to read in the compose resource's directory.
+     * @return The content of the file as a byte array.
+     */
+    public suspend fun readBytes(path: String): ByteArray = readResourceBytes(path)
+}

gradle-plugins/compose/src/test/test-projects/misc/emptyResources/gradle.properties

@@ -0,0 +1 @@
+org.gradle.jvmargs=-Xmx8096M

gradle-plugins/compose/src/test/test-projects/misc/emptyResources/settings.gradle.kts

@@ -0,0 +1,22 @@
+rootProject.name = "empty_res"
+pluginManagement {
+    repositories {
+        mavenLocal()
+        gradlePluginPortal()
+        google()
+        maven("https://maven.pkg.jetbrains.space/public/p/compose/dev")
+    }
+    plugins {
+        id("org.jetbrains.kotlin.multiplatform").version("KOTLIN_VERSION_PLACEHOLDER")
+        id("org.jetbrains.compose").version("COMPOSE_GRADLE_PLUGIN_VERSION_PLACEHOLDER")
+    }
+}
+dependencyResolutionManagement {
+    repositories {
+        mavenLocal()
+        maven("https://maven.pkg.jetbrains.space/public/p/compose/dev")
+        mavenCentral()
+        gradlePluginPortal()
+        google()
+    }
+}

gradle-plugins/compose/src/test/test-projects/misc/emptyResources/src/commonMain/kotlin/App.kt

@@ -0,0 +1,9 @@
+import androidx.compose.material.Text
+import androidx.compose.runtime.Composable
+import app.group.empty_res.generated.resources.Res
+
+@Composable
+fun App() {
+    val res = Res
+    Text("text")
+}