Perform an no-op transformation

Author: Chao Zhang

build.gradle

@@ -1,13 +1,14 @@
 plugins {
     id 'org.jetbrains.kotlin.jvm' version '1.4.31'
+    id 'org.jetbrains.dokka' version '1.4.30'
     id 'java-gradle-plugin'
+    id 'com.vanniktech.maven.publish' version '0.13.0'
 }
 
-group 'io.github.chao2zhang.logginglivedata'
-version '1.0-SNAPSHOT'
-
 repositories {
     mavenCentral()
+    google()
+    jcenter()
 }
 
 gradlePlugin {
@@ -19,6 +20,13 @@ gradlePlugin {
     }
 }
 
+compileJava {
+    sourceCompatibility = '1.8'
+    targetCompatibility = '1.8'
+}
+
 dependencies {
-    implementation "org.jetbrains.kotlin:kotlin-stdlib"
+    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7"
+    implementation 'com.android.tools.build:gradle-api:4.1.3'
+    compileOnly 'com.android.tools.build:gradle:4.1.3'
 }

gradle.properties

@@ -1 +1,5 @@
-kotlin.code.style=official
+kotlin.code.style=official
+
+GROUP=io.github.chao2zhang.logginglivedata
+POM_ARTIFACT_ID=logginglivedata
+VERSION_NAME=0.0.1

gradle/wrapper/gradle-wrapper.properties

@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-6.7-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.8.3-all.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists

src/main/kotlin/io/github/chao2zhang/LoggingLiveDataPlugin.kt

@@ -1,11 +1,17 @@
 package io.github.chao2zhang
 
+import com.android.build.gradle.AppExtension
+import com.android.build.gradle.AppPlugin
 import org.gradle.api.Plugin
 import org.gradle.api.Project
 
 class LoggingLiveDataPlugin : Plugin<Project> {
 
-    override fun apply(p0: Project) {
-        TODO("Not yet implemented")
+    override fun apply(project: Project) {
+        project.plugins.withType(AppPlugin::class.java) { plugin ->
+            project.extensions.configure(AppExtension::class.java) { appExtension ->
+                appExtension.registerTransform(LoggingLiveDataTransform(project.logger))
+            }
+        }
     }
 }

src/main/kotlin/io/github/chao2zhang/LoggingLiveDataTransform.kt

@@ -0,0 +1,90 @@
+package io.github.chao2zhang
+
+import com.android.build.api.transform.Format
+import com.android.build.api.transform.JarInput
+import com.android.build.api.transform.QualifiedContent
+import com.android.build.api.transform.Status
+import com.android.build.api.transform.Transform
+import com.android.build.api.transform.TransformInput
+import com.android.build.api.transform.TransformInvocation
+import com.android.build.api.variant.VariantInfo
+import org.gradle.api.logging.Logger
+import java.io.BufferedOutputStream
+import java.io.File
+import java.io.FileOutputStream
+import java.util.zip.ZipEntry
+import java.util.zip.ZipFile
+import java.util.zip.ZipOutputStream
+
+@Suppress("UnstableApiUsage")
+class LoggingLiveDataTransform(private val logger: Logger) : Transform() {
+
+    override fun getName(): String = javaClass.simpleName
+
+    override fun applyToVariant(variant: VariantInfo) = variant.isDebuggable
+
+    override fun getInputTypes(): Set<QualifiedContent.ContentType> =
+        setOf(QualifiedContent.DefaultContentType.CLASSES)
+
+    override fun getScopes(): MutableSet<in QualifiedContent.Scope> =
+        mutableSetOf(QualifiedContent.Scope.EXTERNAL_LIBRARIES)
+
+    override fun isIncremental(): Boolean = true
+
+    override fun transform(transformInvocation: TransformInvocation) {
+        super.transform(transformInvocation)
+        transformInvocation.inputs.forEach {
+            transform(transformInvocation, it)
+        }
+    }
+
+    private fun transform(transformInvocation: TransformInvocation, transformInput: TransformInput) {
+        transformInput.jarInputs.forEach { jarInput ->
+            val inputJar = jarInput.file
+            val outputJar = transformInvocation.outputProvider.getContentLocation(
+                jarInput.name,
+                jarInput.contentTypes,
+                jarInput.scopes,
+                Format.JAR
+            )
+            logger.lifecycle("Transforming ${jarInput.file}")
+            if (transformInvocation.isIncremental) {
+                when (jarInput.status) {
+                    Status.ADDED, Status.CHANGED -> transformJarInput(jarInput, inputJar, outputJar)
+                    Status.REMOVED -> outputJar.delete()
+                    else -> { }
+                }
+            } else {
+                transformJarInput(jarInput, inputJar, outputJar)
+            }
+        }
+    }
+
+    private fun transformJarInput(jarInput: JarInput, inputJar: File, outputJar: File) {
+        if (jarInput.isLiveDataJarInput()) {
+            transformLiveDataJar(inputJar, outputJar)
+        } else {
+            inputJar.copyTo(outputJar, overwrite = true)
+        }
+    }
+
+    private fun transformLiveDataJar(inputJar: File, outputJar: File) {
+        val inputZip = ZipFile(inputJar)
+        val outputZip = ZipOutputStream(BufferedOutputStream(FileOutputStream(outputJar)))
+        val inputEntries = inputZip.entries()
+        while (inputEntries.hasMoreElements()) {
+            val inputEntry = inputEntries.nextElement()
+            val outputEntry = ZipEntry(inputEntry.name)
+            with(outputZip) {
+                putNextEntry(outputEntry)
+                write(inputZip.getInputStream(inputEntry).readAllBytes())
+                closeEntry()
+            }
+        }
+        outputZip.flush()
+        outputZip.close()
+    }
+
+    private fun JarInput.isLiveDataJarInput(): Boolean =
+        name.startsWith("androidx.lifecycle:lifecycle-livedata:")
+}