KT-31127: register only generated Java sources to AGP

When adding generated Java sources to AGP using Variant API,
add only Java sources. This was already done in
a6ae4494167c9d4cca23995457c59fb2daedad39 for Java projects, and this
commit fixes the same issue for Android projects.

Test: Kapt3Android33IT.testKotlinProcessorUsingFiler

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/Kapt3AndroidIT.kt

@@ -1,11 +1,10 @@
 package org.jetbrains.kotlin.gradle
 
-import org.jetbrains.kotlin.gradle.util.AGPVersion
-import org.jetbrains.kotlin.gradle.util.checkedReplace
-import org.jetbrains.kotlin.gradle.util.getFileByName
-import org.jetbrains.kotlin.gradle.util.modify
+import org.jetbrains.kotlin.gradle.util.*
 import org.jetbrains.kotlin.test.KotlinTestUtils
+import org.junit.Assert
 import org.junit.Test
+import java.io.File
 
 class Kapt3WorkersAndroid32IT : Kapt3Android32IT() {
     override fun kaptOptions(): KaptOptions =
@@ -36,6 +35,44 @@ open class Kapt3Android33IT : Kapt3AndroidIT() {
             assertFileExists("build/tmp/kotlin-classes/debug/test/androidx/navigation/StartFragmentKt.class")
         }
     }
+
+    /** Regression test for Android projects and KT-31127. */
+    @Test
+    fun testKotlinProcessorUsingFiler() {
+        val project = Project("AndroidLibraryKotlinProject").apply {
+            setupWorkingDir()
+            gradleBuildScript().appendText(
+                """
+                apply plugin: 'kotlin-kapt'
+                android {
+                    defaultConfig.javaCompileOptions.annotationProcessorOptions.includeCompileClasspath = false
+
+                    libraryVariants.all {
+                        it.generateBuildConfig.enabled = false
+                    }
+                }
+
+                dependencies {
+                    kapt "org.jetbrains.kotlin:annotation-processor-example:${"$"}kotlin_version"
+                    implementation "org.jetbrains.kotlin:annotation-processor-example:${"$"}kotlin_version"
+                }
+            """.trimIndent()
+            )
+
+            // The test must not contain any java sources in order to detect the issue.
+            Assert.assertEquals(emptyList<File>(), projectDir.allJavaFiles().toList())
+            projectDir.getFileByName("Dummy.kt").modify {
+                it.replace("class Dummy", "@example.KotlinFilerGenerated class Dummy")
+            }
+        }
+
+        project.build("assembleDebug") {
+            assertSuccessful()
+            assertFileExists("build/generated/source/kapt/debug/demo/DummyGenerated.kt")
+            assertTasksExecuted(":compileDebugKotlin")
+            assertTasksSkipped(":compileDebugJavaWithJavac")
+        }
+    }
 }
 
 class Kapt3Android31IT : Kapt3AndroidIT() {

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/AndroidLibraryKotlinProject/build.gradle

@@ -0,0 +1,29 @@
+buildscript {
+    repositories {
+        mavenLocal()
+        maven { url 'https://maven.google.com' }
+        jcenter()
+    }
+    dependencies {
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
+        classpath('com.android.tools.build:gradle:' + android_tools_version)
+    }
+}
+
+repositories {
+    mavenLocal()
+    maven { url 'https://maven.google.com' }
+    jcenter()
+}
+
+apply plugin: 'com.android.library'
+apply plugin: 'kotlin-android'
+
+android {
+    compileSdkVersion 23
+    buildToolsVersion "25.0.2"
+}
+
+dependencies {
+    compile "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/AndroidLibraryKotlinProject/gradle.properties

@@ -0,0 +1 @@
+org.gradle.jvmargs=-XX:MaxPermSize=512m

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/AndroidLibraryKotlinProject/src/main/AndroidManifest.xml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+          package="org.jetbrains.kotlin.gradle.test.android.libalfa"
+          android:versionCode="1"
+          android:versionName="1.0" >
+
+  <application/>
+
+</manifest>

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/AndroidLibraryKotlinProject/src/main/kotlin/Dummy.kt

@@ -0,0 +1,3 @@
+package demo
+
+class Dummy

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/AndroidLibraryKotlinProject/src/main/kotlin/Greeter.kt

@@ -0,0 +1,3 @@
+package demo
+
+open class Greeter(val greeting: String)

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/AndroidLibraryKotlinProject/src/main/kotlin/dummyUtil.kt

@@ -0,0 +1,3 @@
+package demo
+
+fun dummyFun() {}

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/targets/android/Android25ProjectHandler.kt

@@ -191,6 +191,7 @@ class Android25ProjectHandler(
             javaTask: AbstractCompile
         ) {
             val kaptSourceOutput = project.fileTree(kaptTask.destinationDir).builtBy(kaptTask)
+            kaptSourceOutput.include("**/*.java")
             variantData.registerExternalAptJavaOutput(kaptSourceOutput)
             variantData.dataBindingDependencyArtifactsIfSupported?.let { kaptTask.dependsOn(it) }
         }