Load kotlin.incremental from local.properties file too

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

@@ -53,6 +53,7 @@ const val ANNOTATIONS_PLUGIN_NAME = "org.jetbrains.kotlin.kapt"
 const val KOTLIN_BUILD_DIR_NAME = "kotlin"
 const val CACHES_DIR_NAME = "caches"
 const val DIRTY_SOURCES_FILE_NAME = "dirty-sources.txt"
+const val USING_EXPERIMENTAL_INCREMENTAL_MESSAGE = "Using experimental kotlin incremental compilation"
 
 abstract class AbstractKotlinCompile<T : CommonCompilerArguments>() : AbstractCompile() {
     abstract protected val compiler: CLICompiler<T>
@@ -360,7 +361,7 @@ open class KotlinCompile() : AbstractKotlinCompile<K2JVMCompilerArguments>() {
             return
         }
 
-        logger.warn("Using experimental kotlin incremental compilation")
+        logger.warn(USING_EXPERIMENTAL_INCREMENTAL_MESSAGE)
         anyClassesCompiled = false
         // TODO: decide what to do if no files are considered dirty - rebuild or skip the module
         var (sourcesToCompile, isIncrementalDecided) = calculateSourcesToCompile()

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

@@ -2,10 +2,16 @@ package org.jetbrains.kotlin.gradle.plugin
 
 import org.gradle.api.Project
 import org.gradle.api.tasks.compile.AbstractCompile
+import java.util.*
 
 fun mapKotlinTaskProperties(project: Project, task: AbstractCompile) {
-    for (mapping in propertyMappings) {
-        mapping.apply(project, task)
+    propertyMappings.forEach { it.apply(project, task) }
+
+    val localPropertiesFile = project.rootProject.file("local.properties")
+    if (localPropertiesFile.isFile) {
+        val properties = Properties()
+        properties.load(localPropertiesFile.inputStream())
+        propertyMappings.forEach { it.apply(properties, task) }
     }
 }
 
@@ -21,7 +27,16 @@ private class KotlinPropertyMapping<T>(
     fun apply(project: Project, task: AbstractCompile) {
         if (!project.hasProperty(projectPropName)) return
 
-        val value = project.property(projectPropName) as? String ?: return
+        setPropertyValue(task, project.property(projectPropName))
+    }
+
+    fun apply(properties: Properties, task: AbstractCompile) {
+        setPropertyValue(task, properties.getProperty(projectPropName))
+    }
+
+    private fun setPropertyValue(task: AbstractCompile, value: Any?) {
+        if (value !is String) return
+
         val transformedValue = transform(value) ?: return
         task.setProperty(taskPropName, transformedValue)
     }

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

@@ -2,6 +2,7 @@ package org.jetbrains.kotlin.gradle
 
 import org.gradle.api.logging.LogLevel
 import org.jetbrains.kotlin.gradle.plugin.CleanUpBuildListener
+import org.jetbrains.kotlin.gradle.tasks.USING_EXPERIMENTAL_INCREMENTAL_MESSAGE
 import org.junit.Test
 import java.io.File
 import kotlin.test.assertTrue
@@ -269,4 +270,17 @@ class KotlinGradleIT: BaseGradleIT() {
             assertFileExists("build/classes/main/example/TestClassCustomized.class")
         }
     }
+
+    @Test
+    fun testIncrementalPropertyFromLocalPropertiesFile() {
+        val project = Project("kotlinProject", "2.10")
+        project.setupWorkingDir()
+
+        val localPropertyFile = File(project.projectDir, "local.properties")
+        localPropertyFile.writeText("kotlin.incremental=true")
+
+        project.build("build") {
+            assertContains(USING_EXPERIMENTAL_INCREMENTAL_MESSAGE)
+        }
+    }
 }