CheckAsmTransformationTask.kt

/*
 * Copyright (C) 2024 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import org.gradle.api.DefaultTask
import org.gradle.api.tasks.InputFiles
import org.gradle.api.file.DirectoryProperty
import org.gradle.api.file.Directory
import org.gradle.api.file.RegularFile
import org.gradle.api.provider.ListProperty
import org.gradle.api.tasks.OutputDirectory
import org.gradle.api.tasks.PathSensitive
import org.gradle.api.tasks.PathSensitivity
import org.gradle.api.tasks.TaskAction
import org.objectweb.asm.ClassReader
import org.objectweb.asm.tree.ClassNode
import org.objectweb.asm.Opcodes

/**
 * This task does a trivial verification of the ASM transformation on the classes.
 */
abstract class CheckAsmTransformationTask : DefaultTask() {

    // In order for the task to be up-to-date when the inputs have not changed,
    // the task must declare an output, even if it's not used. Tasks with no
    // output are always run regardless of whether the inputs changed
    @get:OutputDirectory
    abstract val output: DirectoryProperty

    /**
     * Project scope, not including dependencies.
     */
    @get:InputFiles
    @get:PathSensitive(PathSensitivity.RELATIVE)
    abstract val projectDirectories: ListProperty<Directory>

    /**
     * Project scope, not including dependencies.
     */
    @get:InputFiles
    @get:PathSensitive(PathSensitivity.NONE)
    abstract val projectJars: ListProperty<RegularFile>

    @TaskAction
    fun taskAction() {
        val someSourceClassFile =
            projectDirectories.get().first().file("com/example/android/recipes/sample/SomeSource.class")
        val classReader = ClassReader(someSourceClassFile.asFile.readBytes())
        val classNode = ClassNode(Opcodes.ASM9)
        classReader.accept(classNode, 0)
        if (classNode.methods.find { it.name == "transformedMethod" } == null) {
            throw RuntimeException("Transformed method not found.")
        }
    }
}