Filling in and reverting annotationProcessor

Added reverting processor path back.
Appending processor path instead of setting it.

Issues: #KT-17255 Fixed

(cherry picked from commit 843844b)

Added a test checking that -processorpath is set for all Gradle versions

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

@@ -218,6 +218,11 @@ abstract class BaseGradleIT {
         return this
     }
 
+    fun CompiledProject.assertContainsRegex(expected: Regex): CompiledProject {
+        assertTrue(expected.containsMatchIn(output), "Output should contain pattern '$expected'")
+        return this
+    }
+
     fun CompiledProject.assertClassFilesNotContain(dir: File, vararg strings: String) {
         val classFiles = dir.walk().filter { it.isFile && it.extension.toLowerCase() == "class" }
 

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

@@ -5,6 +5,19 @@ import org.junit.Test
 import java.io.File
 
 class KotlinGradlePluginMultiVersionIT : BaseMultiGradleVersionIT() {
+    @Test
+    fun testKaptProcessorPath() {
+        val project = Project("kaptSimple", gradleVersion)
+
+        project.build("build") {
+            assertSuccessful()
+            assertContains()
+            assertContainsRegex("""-processorpath \S*.build.tmp.kapt.main.wrappers""".toRegex())
+            assertFileExists("build/generated/source/kapt/main/example/TestClassGenerated.java")
+            assertClassFilesNotContain(File(project.projectDir, "build/classes"), "ExampleSourceAnnotation")
+        }
+    }
+
     @Test
     fun testJavaIcCompatibility() {
         val version = gradleVersion.split(".").map(String::toInt)

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

@@ -136,6 +136,7 @@ class AnnotationProcessingManager(
     val hackAnnotationDir = File(aptWorkingDir, "java_src")
 
     private var originalJavaCompilerArgs: List<String>? = null
+    private var originalProcessorPath: FileCollection? = null
 
     private companion object {
         val JAVA_FQNAME_PATTERN = "^([\\p{L}_$][\\p{L}\\p{N}_$]*\\.)*[\\p{L}_$][\\p{L}\\p{N}_$]*$".toRegex()
@@ -171,7 +172,7 @@ class AnnotationProcessingManager(
 
         generateAnnotationProcessorStubs(javaTask, annotationProcessorFqNames, wrappersDirectory)
 
-        setProcessorPath(javaTask, (kaptProcessorPath))
+        setProcessorPathInJavaTask()
 
         if (aptOutputDir.exists()) {
             aptOutputDir.deleteRecursively()
@@ -190,6 +191,7 @@ class AnnotationProcessingManager(
             project.logger.kotlinDebug("kapt: Java file stub was not found at $generatedFile")
         }
         javaTask.options.compilerArgs = originalJavaCompilerArgs
+        tryRevertProcessorPathProperty()
     }
 
     fun generateJavaHackFile() {
@@ -269,21 +271,45 @@ class AnnotationProcessingManager(
         }
     }
 
-    private fun setProcessorPath(javaTask: JavaCompile, path: Iterable<File>) {
-        javaTask.addCompilerArgument("-processorpath") { prevValue ->
-            if (prevValue != null)
-                javaTask.logger.warn("Processor path was modified by kapt. Previous value = $prevValue")
-            path.joinToString(File.pathSeparator)
+    private fun setProcessorPathInJavaTask() {
+        val path = kaptProcessorPath
+
+        // If processor path property is supported, set it, otherwise set compiler argument:
+        val couldSetProperty = tryAppendProcessorPathProperty(path)
+
+        if (!couldSetProperty) {
+            javaTask.addCompilerArgument("-processorpath") { prevValue ->
+                if (prevValue != null)
+                    javaTask.logger.warn("Processor path was modified by kapt. Previous value = $prevValue")
+                path.joinToString(prefix = prevValue?.let { it + File.pathSeparator }.orEmpty(),
+                                  separator = File.pathSeparator)
+            }
         }
-        // Android Gradle plugin ignores -processorpath: starting with 2.4.0-alpha3, it works with its own options
-        trySetProcessorPathForAndroid(javaTask, path)
     }
 
-    private fun trySetProcessorPathForAndroid(javaTask: JavaCompile, path: Iterable<File>) {
+    private fun tryAppendProcessorPathProperty(path: Iterable<File>): Boolean = try {
         val optionsClass = javaTask.options.javaClass
+        val getPath = optionsClass.getMethod("getAnnotationProcessorPath")
+        val setPath = optionsClass.getMethod("setAnnotationProcessorPath", FileCollection::class.java)
+
+        originalProcessorPath = getPath(javaTask.options) as? FileCollection
+
+        if (originalProcessorPath != null)
+            javaTask.logger.warn("Processor path was modified by kapt. Previous value = $originalProcessorPath")
+
+        val newPath = javaTask.project.files(path + (originalProcessorPath ?: emptyList<File>()))
+        setPath(javaTask.options, newPath)
+        true
+    } catch (_: NoSuchMethodException) {
+        false
+    }
+
+    private fun tryRevertProcessorPathProperty() {
         try {
+            val optionsClass = javaTask.options.javaClass
             val setPath = optionsClass.getMethod("setAnnotationProcessorPath", FileCollection::class.java)
-            setPath(javaTask.options, javaTask.project.files(path))
+
+            setPath(javaTask.options, originalProcessorPath)
         } catch (_: NoSuchMethodException) {
         }
     }