IC: add destination dir to start of classpath instead of end

Otherwise IC fails when a project declares a class with the same name
as in one of its dependencies.
The issue is relevant only for non-JPS IC (Gradle, Maven, etc.),
but I added the test for JPS too.

  #KT-20516 fixed

compiler/incremental-compilation-impl/src/org/jetbrains/kotlin/incremental/IncrementalJvmCompilerRunner.kt

@@ -314,7 +314,9 @@ class IncrementalJvmCompilerRunner(
     override fun preBuildHook(args: K2JVMCompilerArguments, compilationMode: CompilationMode) {
         when (compilationMode) {
             is CompilationMode.Incremental -> {
-                args.classpathAsList += args.destinationAsFile.apply { mkdirs() }
+                val destinationDir = args.destinationAsFile
+                destinationDir.mkdirs()
+                args.classpathAsList = listOf(destinationDir) + args.classpathAsList
             }
             is CompilationMode.Rebuild -> {
                 // there is no point in updating annotation file since all files will be compiled anyway

jps-plugin/jps-tests/test/org/jetbrains/kotlin/jps/build/IncrementalJpsTestGenerated.java

@@ -117,6 +117,12 @@ public class IncrementalJpsTestGenerated extends AbstractIncrementalJpsTest {
             doTest(fileName);
         }
 
+        @TestMetadata("duplicatedClass")
+        public void testDuplicatedClass() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("jps-plugin/testData/incremental/multiModule/duplicatedClass/");
+            doTest(fileName);
+        }
+
         @TestMetadata("exportedDependency")
         public void testExportedDependency() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("jps-plugin/testData/incremental/multiModule/exportedDependency/");

jps-plugin/testData/incremental/multiModule/duplicatedClass/build.log

@@ -0,0 +1,17 @@
+================ Step #1 =================
+
+Building module1
+Exit code: NOTHING_DONE
+------------------------------------------
+Building module2
+Cleaning output files:
+  out/production/module2/META-INF/module2.kotlin_module
+  out/production/module2/UseAKt.class
+  out/production/module2/UseUtilsKt.class
+End of files
+Compiling files:
+  module2/src/useA.kt
+  module2/src/useUtils.kt
+End of files
+Exit code: OK
+------------------------------------------

jps-plugin/testData/incremental/multiModule/duplicatedClass/dependencies.txt

@@ -0,0 +1,2 @@
+module1->
+module2->module1

jps-plugin/testData/incremental/multiModule/duplicatedClass/module1_A.kt

@@ -0,0 +1,3 @@
+class A {
+    fun fizz() {}
+}

jps-plugin/testData/incremental/multiModule/duplicatedClass/module1_other1.kt

@@ -0,0 +1,2 @@
+fun other1() {
+}

jps-plugin/testData/incremental/multiModule/duplicatedClass/module1_utils.kt

@@ -0,0 +1 @@
+fun fizz() {}

jps-plugin/testData/incremental/multiModule/duplicatedClass/module2_A.kt

@@ -0,0 +1,3 @@
+class A {
+    fun buzz() {}
+}

jps-plugin/testData/incremental/multiModule/duplicatedClass/module2_other2.kt

@@ -0,0 +1,2 @@
+fun other2() {
+}

jps-plugin/testData/incremental/multiModule/duplicatedClass/module2_useA.kt

@@ -0,0 +1,3 @@
+fun useA() {
+    A().buzz()
+}

jps-plugin/testData/incremental/multiModule/duplicatedClass/module2_useUtils.kt

@@ -0,0 +1,3 @@
+fun useUtils() {
+    buzz()
+}

jps-plugin/testData/incremental/multiModule/duplicatedClass/module2_utils.kt

@@ -0,0 +1 @@
+fun buzz() {}

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

@@ -22,6 +22,21 @@ class IncrementalCompilationMultiProjectIT : BaseGradleIT() {
     override fun defaultBuildOptions(): BuildOptions =
             super.defaultBuildOptions().copy(withDaemon = true, incremental = true)
 
+    @Test
+    fun testDuplicatedClass() {
+        val project = Project("duplicatedClass")
+        project.build("build") {
+            assertSuccessful()
+        }
+
+        val usagesFiles = listOf("useBuzz.kt", "useA.kt").map { project.projectFile(it) }
+        usagesFiles.forEach { file -> file.modify { "$it\n " } }
+
+        project.build("build") {
+            assertSuccessful()
+            assertCompiledKotlinSources(project.relativize(usagesFiles))
+        }
+    }
 
     @Test
     fun testMoveFunctionFromLib() {

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/duplicatedClass/app/build.gradle

@@ -0,0 +1,5 @@
+apply plugin: 'kotlin'
+
+dependencies {
+    compile project(':lib')
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/duplicatedClass/app/src/main/kotlin/A.kt

@@ -0,0 +1,3 @@
+class A {
+    fun buzz() {}
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/duplicatedClass/app/src/main/kotlin/useA.kt

@@ -0,0 +1,3 @@
+fun useA(a: A) {
+    A().buzz()
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/duplicatedClass/app/src/main/kotlin/useBuzz.kt

@@ -0,0 +1,3 @@
+fun useBuzz() {
+    buzz()
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/duplicatedClass/app/src/main/kotlin/utils.kt

@@ -0,0 +1 @@
+fun buzz() {}

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

@@ -0,0 +1,9 @@
+buildscript {
+    repositories {
+        mavenLocal()
+        mavenCentral()
+    }
+    dependencies {
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
+    }
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/duplicatedClass/lib/build.gradle

@@ -0,0 +1 @@
+apply plugin: 'kotlin'

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/duplicatedClass/lib/src/main/kotlin/A.kt

@@ -0,0 +1,3 @@
+class A {
+    fun fizz() {}
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/duplicatedClass/lib/src/main/kotlin/utils.kt

@@ -0,0 +1 @@
+fun fizz() {}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/duplicatedClass/settings.gradle

@@ -0,0 +1 @@
+include ':lib', ':app'

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

@@ -19,6 +19,8 @@ package org.jetbrains.kotlin.incremental
 import org.gradle.api.Project
 import java.io.File
 
+// todo: Move all files under org.jetbrains.kotlin.gradle package to avoid class clash (KT-18621, KT-20516)
+
 internal fun File.isJavaFile() =
         extension.equals("java", ignoreCase = true)