Gradle Plugin - Linking Generated Java Code to Android Source Set

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Hi,

I’m developing a Gradle plugin that runs a compiler to generate Java code and need to add the generated files to the configured source set.

For Java, I extend each source set with a custom extension for configuration, then link the task output to the Java source set. This works as expected:

fun configure(
    project: Project,
    toolsPath: Provider<String>,
    includeSearchPath: Provider<List<String>>,
    extension: SliceExtension,
    compileSlice: TaskProvider<Task>,
) {
    val javaExtension = project.extensions.findByType(JavaPluginExtension::class.java)
        ?: throw GradleException("JavaPluginExtension is missing. Ensure the Java plugin is applied before configuring Slice Tools.")

    javaExtension.sourceSets.configureEach { sourceSet ->
        val sliceSourceSet = SliceToolsUtil.createSliceSourceSet(extension, sourceSet.name)
        sourceSet.extensions.add("slice", sliceSourceSet)
        val compileTask = SliceToolsUtil.configureSliceTaskForSourceSet(
            project,
            toolsPath,
            includeSearchPath,
            extension,
            sliceSourceSet,
            compileSlice,
        )
        sourceSet.java.srcDir(compileTask.flatMap { it.output })
    }
}

When I run compileJava, the corresponding compileSliceMain task is triggered, and everything works smoothly:

:ice:compileSliceMain SKIPPED
:ice:compileJava SKIPPED

However, I cannot get the Android version to work:

fun configure(
        project: Project,
        toolsPath: Provider<String>,
        includeSearchPath: Provider<List<String>>,
        extension: SliceExtension,
        compileSlice: TaskProvider<Task>,
    ) {
        val androidExtension = project.extensions.findByType(BaseAppModuleExtension::class.java)
            ?: project.extensions.findByType(LibraryExtension::class.java)
            ?: throw GradleException(
                "Android extension is missing. Ensure either the Android application or library plugin is applied.\n" +
                    "Ensure the Android plugin is applied before configuring Slice Tools.",
            )

        // Register Slice source set as "slice" extension of each Android source set
        androidExtension.sourceSets.configureEach { sourceSet ->
            project.logger.lifecycle("Configuring Slice source set for Android source set: ${sourceSet.name}")
            val sliceSourceSet = SliceToolsUtil.createSliceSourceSet(extension, sourceSet.name)

            // Register it as an extension in the Android source set
            (sourceSet as ExtensionAware).extensions.add("slice", sliceSourceSet)

            // Create a compile task for this Slice source set
            val compileTask = SliceToolsUtil.configureSliceTaskForSourceSet(
                project,
                toolsPath,
                includeSearchPath,
                extension,
                sliceSourceSet,
                compileSlice,
            )

            // Link the generated output from Slice compilation to the Android Java sources
            sourceSet.java.srcDir(compileTask.flatMap { it.output })
        }
    }

The issue: When I run the build, my compileSlice tasks are not triggered.

The output directory in the task is declared as:

@get:OutputDirectory
abstract val output: DirectoryProperty

And set during initialization:

init {
        // Ensure the task always runs, preventing Gradle from marking it as UP-TO-DATE. This allow us to check for
        // changes in the Slice files and dependencies.
        outputs.upToDateWhen { false }

        // Set default output directory to `build/generated/source/slice/<sourceSetName>`
        output.convention(
            sourceSetName.flatMap { project.layout.buildDirectory.dir("generated/source/slice/$it") },
        )
    }

Does anyone know what might be preventing the Android source sets from picking up the generated sources?

Any help would be greatly appreciated.

Thanks,

José