Kapt: Add gradle warnings for Android projects

1. When the old kapt (aka kapt1) is used
2. (for Android projects) When Kotlin plugin is applied but annotationProcessor (Java-only) dependencies are found

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/internal/AnnotationProcessingManager.kt

@@ -164,6 +164,9 @@ class AnnotationProcessingManager(
 
         if (aptFiles.isEmpty()) return
 
+        project.logger.warn("${project.name}: " +
+                "Original kapt is deprecated. Please add \"apply plugin: 'kotlin-kapt'\" to your build.gradle.")
+
         if (project.plugins.findPlugin(ANDROID_APT_PLUGIN_ID) != null) {
             project.logger.warn("Please do not use `$ANDROID_APT_PLUGIN_ID` with kapt.")
         }

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/internal/Kapt3KotlinGradleSubplugin.kt

@@ -22,6 +22,7 @@ import com.android.builder.model.SourceProvider
 import org.gradle.api.Plugin
 import org.gradle.api.Project
 import org.gradle.api.artifacts.Configuration
+import org.gradle.api.artifacts.Dependency
 import org.gradle.api.tasks.SourceSet
 import org.gradle.api.tasks.compile.AbstractCompile
 import org.gradle.api.tasks.compile.JavaCompile
@@ -60,6 +61,9 @@ class Kapt3KotlinGradleSubplugin : KotlinGradleSubplugin<KotlinCompile> {
 
         val MAIN_KAPT_CONFIGURATION_NAME = "kapt"
 
+        val KAPT_GROUP_NAME = "org.jetbrains.kotlin"
+        val KAPT_ARTIFACT_NAME = "kotlin-annotation-processing"
+
         fun getKaptConfigurationName(sourceSetName: String): String {
             return if (sourceSetName != "main")
                 "$MAIN_KAPT_CONFIGURATION_NAME${sourceSetName.capitalize()}"
@@ -336,10 +340,29 @@ class Kapt3KotlinGradleSubplugin : KotlinGradleSubplugin<KotlinCompile> {
     }
 
     override fun getCompilerPluginId() = "org.jetbrains.kotlin.kapt3"
-    override fun getGroupName() = "org.jetbrains.kotlin"
-    override fun getArtifactName() = "kotlin-annotation-processing"
+    override fun getGroupName() = KAPT_GROUP_NAME
+    override fun getArtifactName() = KAPT_ARTIFACT_NAME
 }
 
 internal fun registerGeneratedJavaSource(kaptTask: KaptTask, javaTask: AbstractCompile) {
     javaTask.source(kaptTask.destinationDir)
+}
+
+internal fun Configuration.getNamedDependencies(): List<Dependency> = allDependencies.filter { it.group != null && it.name != null }
+
+internal fun checkAndroidAnnotationProcessorDependencyUsage(project: Project) {
+    val isKapt3Enabled = Kapt3GradleSubplugin.isEnabled(project)
+
+    val androidAPDependencies = project.configurations
+            .filter { it.name == "annotationProcessor"
+                    || (it.name.endsWith("AnnotationProcessor") && !it.name.startsWith("_")) }
+            .flatMap { it.getNamedDependencies() }
+
+    if (androidAPDependencies.isNotEmpty()) {
+        val artifactsRendered = androidAPDependencies.joinToString { "'${it.group}:${it.name}:${it.version}'" }
+        val andApplyKapt = if (isKapt3Enabled) "" else " and apply the kapt plugin: \"apply plugin: 'kotlin-kapt'\""
+        project.logger.warn("${project.name}: " +
+                "'androidProcessor' dependencies won't be recognized as kapt annotation processors. " +
+                "Please change the configuration name to 'kapt' for these artifacts: $artifactsRendered$andApplyKapt.")
+    }
 }

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/KotlinPlugin.kt

@@ -29,6 +29,7 @@ import org.jetbrains.kotlin.com.intellij.util.ReflectionUtil
 import org.jetbrains.kotlin.gradle.dsl.KotlinJvmOptionsImpl
 import org.jetbrains.kotlin.gradle.internal.*
 import org.jetbrains.kotlin.gradle.internal.Kapt3KotlinGradleSubplugin.Companion.getKaptClasssesDir
+import org.jetbrains.kotlin.gradle.plugin.android.AndroidGradleWrapper
 import org.jetbrains.kotlin.gradle.tasks.*
 import org.jetbrains.kotlin.gradle.utils.ParsedGradleVersion
 import org.jetbrains.kotlin.incremental.configureMultiProjectIncrementalCompilation
@@ -467,6 +468,8 @@ abstract class AbstractAndroidProjectHandler<V>(private val kotlinConfigurationT
 
                 val subpluginEnvironment = loadSubplugins(project)
 
+                checkAndroidAnnotationProcessorDependencyUsage(project)
+
                 forEachVariant(project) {
                     processVariant(it, project, ext, plugin, aptConfigurations, kotlinOptions,
                             kotlinConfigurationTools.kotlinTasksProvider, subpluginEnvironment)