Build non-incrementally when input class-file is changed

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

@@ -307,7 +307,8 @@ open class KotlinCompile() : AbstractKotlinCompile<K2JVMCompilerArguments>() {
                 // TODO: more precise will be not to rebuild unconditionally on classpath changes, but retrieve lookup info and try to find out which sources are affected by cp changes
                 || isClassPathChanged()
                 // so far considering it not incremental TODO: store java files in the cache and extract removed symbols from it here
-                || removed.any { it.isJavaFile() }
+                || 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")
@@ -376,7 +377,10 @@ open class KotlinCompile() : AbstractKotlinCompile<K2JVMCompilerArguments>() {
                 it.removeClassfilesBySources(removedAndModified)
             }}
 
-            logger.kotlinInfo("compile iteration: ${sourcesToCompile.joinToString{ projectRelativePath(it) }}")
+            // can be empty if only removed sources are present
+            if (sourcesToCompile.isNotEmpty()) {
+                logger.kotlinInfo("compile iteration: ${sourcesToCompile.joinToString { projectRelativePath(it) }}")
+            }
 
             val (existingSource, nonExistingSource) = sourcesToCompile.partition { it.isFile }
             assert(nonExistingSource.isEmpty()) { "Trying to compile removed files: ${nonExistingSource.map(::projectRelativePath)}" }
@@ -710,4 +714,7 @@ internal fun Logger.kotlinDebug(message: ()->String) {
 }
 
 internal fun listClassFiles(path: String): Sequence<File> =
-        File(path).walk().filter { it.isFile && it.extension.toLowerCase() == "class" }
+        File(path).walk().filter { it.isFile && it.hasClassFileExtension() }
+
+private fun File.hasClassFileExtension(): Boolean =
+        extension.toLowerCase() == "class"

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

@@ -86,6 +86,9 @@ abstract class BaseGradleIT {
             copyRecursively(this.resourcesRoot, workingDir)
             copyDirRecursively(File(resourcesRootFile, "GradleWrapper-$wrapperVersion"), projectDir)
         }
+
+        fun relativePaths(files: Iterable<File>): List<String> =
+                files.map { it.relativeTo(projectDir).path }
     }
 
     class CompiledProject(val project: Project, val output: String, val resultCode: Int) {

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

@@ -0,0 +1,88 @@
+package org.jetbrains.kotlin.gradle
+
+import org.jetbrains.kotlin.gradle.util.allKotlinFiles
+import org.jetbrains.kotlin.gradle.util.getFileByName
+import org.jetbrains.kotlin.gradle.util.modify
+import org.junit.Test
+import java.io.File
+
+class TestRootAffectedIT : BaseGradleIT() {
+    @Test
+    fun testSourceRootClassIsModifiedIC() {
+        val project = Project("kotlinProject", "2.10")
+        val buildOptions = defaultBuildOptions().copy(incremental = true)
+
+        project.build("build", options = buildOptions) {
+            assertSuccessful()
+        }
+
+        val kotlinGreetingJoinerFile = project.projectDir.getFileByName("KotlinGreetingJoiner.kt")
+        kotlinGreetingJoinerFile.modify {
+            val replacing   = "fun addName(name: String?): Unit"
+            val replacement = "fun addName(name: String): Unit"
+            assert(it.contains(replacing)) { "API has changed!" }
+            it.replace(replacing, replacement)
+        }
+
+        project.build("build", options = buildOptions) {
+            assertSuccessful()
+            val expectedToCompile = project.relativePaths(listOf(kotlinGreetingJoinerFile) + project.allTestKotlinFiles())
+            assertCompiledKotlinSources(expectedToCompile)
+        }
+
+        project.build("build", options = buildOptions) {
+            assertSuccessful()
+            assertCompiledKotlinSources(emptyList())
+        }
+    }
+
+    @Test
+    fun testSourceRootClassIsRemovedIC() {
+        val project = Project("kotlinProject", "2.10")
+        val buildOptions = defaultBuildOptions().copy(incremental = true)
+
+        project.build("build", options = buildOptions) {
+            assertSuccessful()
+        }
+
+        val dummyFile = project.projectDir.getFileByName("Dummy.kt")
+        dummyFile.delete()
+
+        project.build("build", options = buildOptions) {
+            assertSuccessful()
+            val expectedToCompile = project.relativePaths(project.allTestKotlinFiles())
+            assertCompiledKotlinSources(expectedToCompile)
+        }
+
+        project.build("build", options = buildOptions) {
+            assertSuccessful()
+            assertCompiledKotlinSources(emptyList())
+        }
+    }
+
+    @Test
+    fun testTestRootClassIsRemovedIC() {
+        val project = Project("kotlinProject", "2.10")
+        val buildOptions = defaultBuildOptions().copy(incremental = true)
+
+        project.build("build", options = buildOptions) {
+            assertSuccessful()
+        }
+
+        val greeterTestFile = project.projectDir.getFileByName("TestGreeter.kt")
+        greeterTestFile.delete()
+
+        project.build("build", options = buildOptions) {
+            assertSuccessful()
+            assertCompiledKotlinSources(emptyList())
+        }
+
+        project.build("build", options = buildOptions) {
+            assertSuccessful()
+            assertCompiledKotlinSources(emptyList())
+        }
+    }
+
+    private fun Project.allTestKotlinFiles(): Iterable<File> =
+            File(projectDir, "src/test").allKotlinFiles()
+}

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

@@ -8,6 +8,9 @@ fun File.getFileByName(name: String): File =
 fun File.findFileByName(name: String): File? =
         walk().filter { it.isFile && it.name.equals(name, ignoreCase = true) }.firstOrNull()
 
+fun File.allKotlinFiles(): Iterable<File> =
+        walk().filter { it.isFile && it.extension.toLowerCase().equals("kt") }.toList()
+
 fun File.modify(transform: (String)->String) {
     writeText(transform(readText()))
 }

libraries/tools/kotlin-gradle-plugin/src/test/resources/testProject/kotlinProject/src/main/kotlin/Greeter.kt

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

libraries/tools/kotlin-gradle-plugin/src/test/resources/testProject/kotlinProject/src/main/kotlin/KotlinGreetingJoiner.kt

@@ -1,22 +1,18 @@
 package demo
 
-import com.google.common.primitives.Ints
 import com.google.common.base.Joiner
 import java.util.ArrayList
 
-class KotlinGreetingJoiner(val greeter : Greeter) {
+class KotlinGreetingJoiner(val greeter: Greeter) {
-
     val names = ArrayList<String?>()
 
-    fun addName(name : String?): Unit{
+    fun addName(name: String?): Unit {
         names.add(name)
     }
 
-    fun getJoinedGreeting() : String? {
+    fun getJoinedGreeting(): String? {
         val joiner = Joiner.on(" and ").skipNulls();
         return "${greeter.greeting} ${joiner.join(names)}"
     }
 }
 
-public open class Greeter(val greeting : String)
-

libraries/tools/kotlin-gradle-plugin/src/test/resources/testProject/kotlinProject/src/test/kotlin/TestGreeter.kt

@@ -0,0 +1,10 @@
+package demo
+
+import org.testng.Assert.assertEquals
+
+class TestGreeter {
+    fun test() {
+       val greeter = Greeter("Hi!")
+        assertEquals("Hi!", greeter.greeting)
+    }
+}

libraries/tools/kotlin-gradle-plugin/src/test/resources/testProject/kotlinProject/src/test/kotlin/TestKotlinGreetingJoiner.kt

@@ -1,18 +1,14 @@
 package demo 
 
-import com.google.common.primitives.Ints
+import org.testng.Assert.assertEquals
-import com.google.common.base.Joiner
-import org.testng.Assert.*
-import org.testng.annotations.AfterMethod
-import org.testng.annotations.BeforeMethod
 import org.testng.annotations.Test as test
 
-class TestSource() {
+class TestKotlinGreetingJoiner() {
-    @test fun f() {
+    @test
+    fun test() {
         val example : KotlinGreetingJoiner = KotlinGreetingJoiner(Greeter("Hi"))
         example.addName("Harry")
         example.addName("Ron")
-        example.addName(null)
         example.addName("Hermione")
 
         assertEquals(example.getJoinedGreeting(), "Hi Harry and Ron and Hermione")