Kapt: Using 'kapt' configuration without the 'kotlin-kapt' plugin applied should throw an error (KT-26145)

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/Kapt3IT.kt

@@ -394,6 +394,16 @@ open class Kapt3IT : Kapt3BaseIT() {
         }
     }
 
+    @Test
+    fun testNoKaptPluginApplied() {
+        val project = Project("nokapt", directoryPrefix = "kapt2")
+
+        project.build("build") {
+            assertFailed()
+            assertContains("Could not find method kapt() for arguments")
+        }
+    }
+
     @Test
     fun testChangesInLocalAnnotationProcessor() {
         val project = Project("localAnnotationProcessor", directoryPrefix = "kapt2")

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/kapt2/nokapt/build.gradle

@@ -0,0 +1,26 @@
+buildscript {
+    repositories {
+        mavenLocal()
+        mavenCentral()
+    }
+    dependencies {
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
+    }
+}
+
+apply plugin: "java"
+apply plugin: "kotlin"
+
+repositories {
+    mavenLocal()
+    mavenCentral()
+}
+
+dependencies {
+    compile "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
+    compile "org.jetbrains.kotlin:annotation-processor-example:$kotlin_version"
+    kapt "org.jetbrains.kotlin:annotation-processor-example:$kotlin_version"
+    testCompile 'junit:junit:4.12'
+}
+
+compileKotlin.kotlinOptions.allWarningsAsErrors = true

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/kapt2/nokapt/src/main/java/foo.kt

@@ -0,0 +1 @@
+fun main(args: Array<String>) {}

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

@@ -100,7 +100,7 @@ class Kapt3KotlinGradleSubplugin : KotlinGradleSubplugin<KotlinCompile> {
         val KAPT_SUBPLUGIN_ID = "org.jetbrains.kotlin.kapt3"
 
         fun getKaptConfigurationName(sourceSetName: String): String {
-            return if (sourceSetName != "main")
+            return if (sourceSetName != SourceSet.MAIN_SOURCE_SET_NAME)
                 "$MAIN_KAPT_CONFIGURATION_NAME${sourceSetName.capitalize()}"
             else
                 MAIN_KAPT_CONFIGURATION_NAME
@@ -122,7 +122,7 @@ class Kapt3KotlinGradleSubplugin : KotlinGradleSubplugin<KotlinCompile> {
             return hasProperty(INFO_AS_WARNINGS) && property(INFO_AS_WARNINGS) == "true"
         }
 
-        fun findMainKaptConfiguration(project: Project) = project.findKaptConfiguration(MAIN_KAPT_CONFIGURATION_NAME)
+        fun findMainKaptConfiguration(project: Project) = project.findKaptConfiguration(SourceSet.MAIN_SOURCE_SET_NAME)
 
         fun createAptConfigurationIfNeeded(project: Project, sourceSetName: String): Configuration {
             val configurationName = Kapt3KotlinGradleSubplugin.getKaptConfigurationName(sourceSetName)

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

@@ -161,7 +161,10 @@ internal class Kotlin2JvmSourceSetProcessor(
         tasksProvider.createKotlinJVMTask(project, taskName, kotlinCompilation)
 
     override fun doTargetSpecificProcessing() {
-        Kapt3KotlinGradleSubplugin.createAptConfigurationIfNeeded(project, kotlinCompilation.compilationName)
+        ifKaptEnabled(project) {
+            Kapt3KotlinGradleSubplugin.createAptConfigurationIfNeeded(project, kotlinCompilation.compilationName)
+        }
+
         ScriptingGradleSubplugin.createDiscoveryConfigurationIfNeeded(project, kotlinCompilation.compilationName)
 
         project.afterEvaluate { project ->
@@ -662,7 +665,10 @@ abstract class AbstractAndroidProjectHandler<V>(private val kotlinConfigurationT
                 kotlin.srcDirs(sourceSet.java.srcDirs)
             }
             sourceSet.addConvention(KOTLIN_DSL_NAME, kotlinSourceSet)
-            Kapt3KotlinGradleSubplugin.createAptConfigurationIfNeeded(project, sourceSet.name)
+
+            ifKaptEnabled(project) {
+                Kapt3KotlinGradleSubplugin.createAptConfigurationIfNeeded(project, sourceSet.name)
+            }
         }
 
         val kotlinOptions = KotlinJvmOptionsImpl()
@@ -840,6 +846,19 @@ internal fun createSyncOutputTask(
     return syncTask
 }
 
+private fun ifKaptEnabled(project: Project, block: () -> Unit) {
+    var triggered = false
+
+    fun trigger() {
+        if (triggered) return
+        triggered = true
+        block()
+    }
+
+    project.pluginManager.withPlugin("kotlin-kapt") { trigger() }
+    project.pluginManager.withPlugin("org.jetbrains.kotlin.kapt") { trigger() }
+}
+
 private fun SourceSet.clearJavaSrcDirs() {
     java.setSrcDirs(emptyList<File>())
 }