Refactor version checking

libraries/tools/kotlin-gradle-plugin-core/src/main/kotlin/org/jetbrains/kotlin/gradle/tasks/Tasks.kt

@@ -66,6 +66,14 @@ abstract class AbstractKotlinCompile<T : CommonCompilerArguments>() : AbstractCo
     // indicates that task should compile kotlin incrementally if possible
     // it's not possible when IncrementalTaskInputs#isIncremental returns false (i.e first build)
     var incremental: Boolean = false
+        get() = field
+        set(value) {
+            field = value
+            logger.kotlinDebug { "Set $this.incremental=$value" }
+            System.setProperty("kotlin.incremental.compilation", value.toString())
+            System.setProperty("kotlin.incremental.compilation.experimental", value.toString())
+        }
+
     var kotlinOptions: T = createBlankArgs()
     var compilerCalled: Boolean = false
     // TODO: consider more reliable approach (see usage)
@@ -152,6 +160,9 @@ open class KotlinCompile() : AbstractKotlinCompile<K2JVMCompilerArguments>() {
                dataContainerCacheVersion(taskBuildDirectory),
                gradleCacheVersion(taskBuildDirectory))
     }
+    val isCacheFormatUpToDate: Boolean by lazy {
+        cacheVersions.all { it.checkVersion() == CacheVersion.Action.DO_NOTHING }
+    }
 
     private var kaptAnnotationsFileUpdater: AnnotationFileUpdater? = null
     private val additionalClasspath = arrayListOf<File>()
@@ -291,7 +302,6 @@ open class KotlinCompile() : AbstractKotlinCompile<K2JVMCompilerArguments>() {
                 // so far considering it not incremental TODO: store java files in the cache and extract removed symbols from it here
                 || removed.any { it.isJavaFile() || it.hasClassFileExtension() }
                 || modified.any { it.hasClassFileExtension() }
-                || cacheVersions.any { it.checkVersion() != CacheVersion.Action.DO_NOTHING }
             ) {
                 logger.kotlinInfo(if (!isIncrementalRequested) "clean caches on rebuild" else "classpath changed, rebuilding all kotlin files")
                 targets.forEach { getIncrementalCache(it).clean() }
@@ -333,7 +343,10 @@ open class KotlinCompile() : AbstractKotlinCompile<K2JVMCompilerArguments>() {
                 ExitCode.COMPILATION_ERROR -> throw GradleException("Compilation error. See log for more details")
                 ExitCode.INTERNAL_ERROR -> throw GradleException("Internal compiler error. See log for more details")
                 ExitCode.SCRIPT_EXECUTION_ERROR -> throw GradleException("Script execution error. See log for more details")
-                ExitCode.OK -> logger.kotlinInfo("Compilation succeeded")
+                ExitCode.OK -> {
+                    cacheVersions.forEach { it.saveIfNeeded() }
+                    logger.kotlinInfo("Compilation succeeded")
+                }
             }
         }
 
@@ -395,7 +408,6 @@ open class KotlinCompile() : AbstractKotlinCompile<K2JVMCompilerArguments>() {
                                                             getIncrementalCache = { caches[it]!! })
 
             lookupStorage.update(lookupTracker, sourcesToCompile, currentRemoved)
-            cacheVersions.forEach { it.saveIfNeeded() }
 
             if (!isIncrementalDecided) break
 

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

@@ -1,10 +1,11 @@
 package org.jetbrains.kotlin.gradle.plugin
 
 import org.gradle.api.Project
-import org.gradle.api.tasks.compile.AbstractCompile
+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
 import java.util.*
+import kotlin.reflect.KMutableProperty1
 
-fun mapKotlinTaskProperties(project: Project, task: AbstractCompile) {
+fun mapKotlinTaskProperties(project: Project, task: KotlinCompile) {
     propertyMappings.forEach { it.apply(project, task) }
 
     val localPropertiesFile = project.rootProject.file("local.properties")
@@ -16,28 +17,28 @@ fun mapKotlinTaskProperties(project: Project, task: AbstractCompile) {
 }
 
 private val propertyMappings = listOf(
-        KotlinPropertyMapping("kotlin.incremental", "incremental", String::toBoolean)
+        KotlinPropertyMapping("kotlin.incremental", KotlinCompile::incremental, String::toBoolean)
 )
 
 private class KotlinPropertyMapping<T>(
         private val projectPropName: String,
-        private val taskPropName: String,
+        private val taskProperty: KMutableProperty1<KotlinCompile, T>,
         private val transform: (String) -> T
 ) {
-    fun apply(project: Project, task: AbstractCompile) {
+    fun apply(project: Project, task: KotlinCompile) {
         if (!project.hasProperty(projectPropName)) return
 
         setPropertyValue(task, project.property(projectPropName))
     }
 
-    fun apply(properties: Properties, task: AbstractCompile) {
+    fun apply(properties: Properties, task: KotlinCompile) {
         setPropertyValue(task, properties.getProperty(projectPropName))
     }
 
-    private fun setPropertyValue(task: AbstractCompile, value: Any?) {
+    private fun setPropertyValue(task: KotlinCompile, value: Any?) {
         if (value !is String) return
 
         val transformedValue = transform(value) ?: return
-        task.setProperty(taskPropName, transformedValue)
+        taskProperty.set(task, transformedValue)
     }
 }

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

@@ -10,6 +10,7 @@ open class KotlinTasksProvider {
         return project.tasks.create(name, KotlinCompile::class.java).apply {
             friendTaskName = taskToFriendTaskMapper[this]
             mapKotlinTaskProperties(project, this)
+            outputs.upToDateWhen { isCacheFormatUpToDate }
         }
     }
 

libraries/tools/kotlin-gradle-plugin/src/test/kotlin/org/jetbrains/kotlin/gradle/CacheVersionChangedIT.kt

@@ -1,7 +1,5 @@
 package org.jetbrains.kotlin.gradle
 
-import org.jetbrains.kotlin.gradle.util.getFileByName
-import org.jetbrains.kotlin.gradle.util.modify
 import org.junit.Test
 import java.io.File
 import kotlin.test.assertNotEquals
@@ -43,25 +41,19 @@ class CacheVersionChangedIT : BaseGradleIT() {
         val modifiedVersion = "777"
         versionFile.writeText(modifiedVersion)
 
-        // gradle won't call kotlin task if no file is changed
-        val dummyKtFile = project.projectDir.getFileByName("Dummy.kt")
-        dummyKtFile.modify { it + " " }
-
         project.build("build", options = options) {
             assertSuccessful()
             assertNotEquals(modifiedVersion, versionFile.readText(), "${versionFile.projectPath()} was not rewritten by build")
 
             val mainDir = File(project.projectDir, "src/main")
             val mainKotlinFiles = mainDir.walk().filter { it.isFile && it.extension.equals("kt", ignoreCase = true) }
-            val mainKotlinRelativePaths = mainKotlinFiles.map { it.projectPath() }.toList()
+            val mainKotlinRelativePaths = mainKotlinFiles.map(File::projectPath).toList()
             assertCompiledKotlinSources(mainKotlinRelativePaths)
         }
 
-        dummyKtFile.modify { it + " " }
-
         project.build("build", options = options) {
             assertSuccessful()
-            assertCompiledKotlinSources(listOf(dummyKtFile.projectPath()))
+            assertCompiledKotlinSources(listOf(), weakTesting = false)
         }
     }
 }