Add test to validate incremental changes in compiler plugin.

If compiler plugin was recompiled incrementally, other projects in the
same build should pick it up and regenerate sources.

^KT-38570 Fixed

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

@@ -0,0 +1,67 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.gradle
+
+import org.gradle.util.GradleVersion
+import org.jetbrains.kotlin.gradle.testbase.*
+import org.junit.jupiter.api.DisplayName
+import kotlin.io.path.exists
+
+@DisplayName("Compiler plugin incremental compilation")
+@OtherGradlePluginTests
+class CompilerPluginsIncrementalIT : KGPBaseTest() {
+    override val defaultBuildOptions: BuildOptions
+        get() = super.defaultBuildOptions.copy(
+            incremental = true
+        )
+
+    @DisplayName("KT-38570: After changing compiler plugin code, next incremental build picks it up")
+    @GradleTest
+    internal fun afterChangeInPluginBuildDoesIncrementalProcessing(gradleVersion: GradleVersion) {
+        project("incrementalChangeInPlugin".prefix, gradleVersion) {
+            build("assemble")
+
+            val genDir = subProject("library").projectPath.resolve("build/sample-dir/plugin/test/gen")
+            assert(genDir.exists()) { "$genDir does not exists!" }
+
+            val generatedFiles = genDir.toFile()
+                .walkTopDown()
+                .asSequence()
+                .filterNot { it.isDirectory }
+                .associate {
+                    it.absolutePath to it.readBytes()
+                }
+
+            subProject("plugin")
+                .kotlinSourcesDir()
+                .resolve("test/compiler/plugin/TestComponentRegistrar.kt")
+                .modify {
+                    it.replace("world.", "something else.")
+                }
+
+            build("assemble") {
+                assert(genDir.exists()) { "$genDir does not exists!" }
+            }
+
+            genDir.toFile()
+                .walkTopDown()
+                .asSequence()
+                .filterNot { it.isDirectory }
+                .forEach {
+                    assert(!it.readBytes().contentEquals(generatedFiles[it.absolutePath])) {
+                        """
+                        
+                        File ${it.absolutePath} content is equals to previous one!
+                        New content:
+                        ${it.readText()}
+                        """.trimIndent()
+                    }
+                }
+        }
+    }
+
+    private val String.prefix get() = "compilerPlugins/$this"
+}

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

@@ -0,0 +1,14 @@
+plugins {
+    id 'java'
+    id 'org.jetbrains.kotlin.jvm'
+}
+
+sourceCompatibility = 1.8
+
+allprojects {
+    repositories {
+        mavenLocal()
+        mavenCentral()
+        google()
+    }
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/compilerPlugins/incrementalChangeInPlugin/library/build.gradle

@@ -0,0 +1,7 @@
+plugins {
+    id "org.jetbrains.kotlin.jvm"
+}
+
+dependencies {
+    kotlinCompilerPluginClasspath project(':plugin')
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/compilerPlugins/incrementalChangeInPlugin/library/src/main/kotlin/library/SomeClass.kt

@@ -0,0 +1,8 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package library
+
+class SomeClass

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/compilerPlugins/incrementalChangeInPlugin/library/src/main/kotlin/library/SomeInterface.kt

@@ -0,0 +1,8 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package library
+
+interface SomeInterface

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

@@ -0,0 +1,13 @@
+plugins {
+    id 'org.jetbrains.kotlin.jvm'
+}
+
+dependencies {
+    implementation "org.jetbrains.kotlin:kotlin-gradle-plugin-api"
+
+    compileOnly "org.jetbrains.kotlin:kotlin-compiler-embeddable"
+}
+
+compileKotlin {
+    kotlinOptions.jvmTarget = "1.8"
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/compilerPlugins/incrementalChangeInPlugin/plugin/src/main/kotlin/test/compiler/plugin/TestComponentRegistrar.kt

@@ -0,0 +1,112 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package test.compiler.plugin
+
+import org.jetbrains.kotlin.analyzer.AnalysisResult
+import org.jetbrains.kotlin.analyzer.AnalysisResult.RetryWithAdditionalRoots
+import org.jetbrains.kotlin.cli.common.config.KotlinSourceRoot
+import org.jetbrains.kotlin.cli.common.config.kotlinSourceRoots
+import org.jetbrains.kotlin.com.intellij.mock.MockProject
+import org.jetbrains.kotlin.com.intellij.openapi.project.Project
+import org.jetbrains.kotlin.compiler.plugin.ComponentRegistrar
+import org.jetbrains.kotlin.config.CompilerConfiguration
+import org.jetbrains.kotlin.descriptors.ModuleDescriptor
+import org.jetbrains.kotlin.descriptors.findClassAcrossModuleDependencies
+import org.jetbrains.kotlin.name.ClassId
+import org.jetbrains.kotlin.name.FqName
+import org.jetbrains.kotlin.psi.KtClassOrObject
+import org.jetbrains.kotlin.psi.KtFile
+import org.jetbrains.kotlin.resolve.BindingTrace
+import org.jetbrains.kotlin.resolve.jvm.extensions.AnalysisHandlerExtension
+import java.io.File
+
+class TestComponentRegistrar : ComponentRegistrar {
+    override fun registerProjectComponents(
+        project: MockProject,
+        configuration: CompilerConfiguration
+    ) {
+        val kotlinSourceRoots = configuration.kotlinSourceRoots.ifEmpty { return }
+        val sourceGenFolder = createSourceGenFolder(kotlinSourceRoots)
+
+        var counter = 0
+
+        AnalysisHandlerExtension.registerExtension(project, object : AnalysisHandlerExtension {
+            private var didRecompile = false
+
+            override fun analysisCompleted(
+                project: Project,
+                module: ModuleDescriptor,
+                bindingTrace: BindingTrace,
+                files: Collection<KtFile>
+            ): AnalysisResult? {
+                if (didRecompile) return null
+                didRecompile = true
+
+                val classes = files
+                    .flatMap { ktFile ->
+                        val packageName = ktFile.packageFqName.asString()
+                        ktFile.findChildrenByClass(KtClassOrObject::class.java)
+                            .map { packageName + "." + it.nameAsSafeName.asString() }
+                    }
+                    .mapNotNull {
+                        module.findClassAcrossModuleDependencies(ClassId.topLevel(FqName(it)))
+                    }
+
+                // Nothing to do.
+                if (classes.isEmpty()) return null
+
+                classes.forEach { classDescriptor ->
+                    val className = classDescriptor.name.asString()
+
+                    val directory = File(sourceGenFolder, "plugin/test/gen")
+                    val file = File(directory, "$className.kt")
+                        .also {
+                            check(it.parentFile.exists() || it.parentFile.mkdirs()) {
+                                "Could not generate package directory: $this"
+                            }
+                        }
+
+                    file.writeText(
+                        """
+                  package plugin.test.gen
+                  
+                  val hello${counter++} = "world."
+              """.trimIndent()
+                    )
+                }
+
+                // This restarts the analysis phase and will include our file.
+                return RetryWithAdditionalRoots(
+                    bindingTrace.bindingContext, module, emptyList(), listOf(sourceGenFolder), addToEnvironment = true
+                )
+            }
+        })
+    }
+
+    private fun createSourceGenFolder(kotlinSourceRoots: List<KotlinSourceRoot>): File {
+        fun sampleDir(parent: File): File = File(parent, "sample-dir").also {
+            check(it.exists() || it.mkdirs()) {
+                "Could not create source generation directory: $it"
+            }
+        }
+
+        val oneSourceFile = kotlinSourceRoots.first().path.let { File(it) }
+        val parentSequence = generateSequence(oneSourceFile) { it.parentFile }
+
+        // Try to find the src dir.
+        parentSequence.firstOrNull { it.name == "src" }
+            ?.let { return sampleDir(File(it.parentFile, "build")) }
+
+        // If the src dir is not part of the input (incremental build), look for the build dir
+        // directly.
+        parentSequence.firstOrNull { it.name == "build" }
+            ?.let { return sampleDir(it) }
+
+        throw IllegalStateException(
+            "Could not create source generation directory: $oneSourceFile"
+        )
+    }
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/compilerPlugins/incrementalChangeInPlugin/plugin/src/main/resources/META-INF/services/org.jetbrains.kotlin.compiler.plugin.ComponentRegistrar

@@ -0,0 +1,6 @@
+#
+# Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+# Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+#
+
+test.compiler.plugin.TestComponentRegistrar

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

@@ -0,0 +1,2 @@
+include ':plugin'
+include ':library'