[Gradle] Add tests for KT-62921

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

@@ -0,0 +1,110 @@
+/*
+ * Copyright 2010-2024 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.testkit.runner.BuildResult
+import org.gradle.util.GradleVersion
+import org.jetbrains.kotlin.gradle.internals.KOTLIN_BUILD_TOOLS_API_CLASSPATH_CONFIGURATION_NAME
+import org.jetbrains.kotlin.gradle.testbase.*
+import org.junit.jupiter.api.DisplayName
+
+@DisplayName("Tests for compiler version choosing via the Build Tools API")
+@JvmGradlePluginTests
+class CompilerVersionChooseIT : KGPBaseTest() {
+    override val defaultBuildOptions = super.defaultBuildOptions.copy(runViaBuildToolsApi = true)
+
+    @GradleTest
+    @DisplayName("Verify default compiler dependencies")
+    fun defaultClasspath(gradleVersion: GradleVersion) {
+        prepareProject(gradleVersion) {
+            build(printClasspathTaskName) {
+                assertCompilerVersion(buildOptions.kotlinVersion)
+            }
+        }
+    }
+
+    @GradleTest
+    @DisplayName("Compiler version may be specified via the kotlin extension")
+    fun compilerVersionMayBeChanged(gradleVersion: GradleVersion) {
+        prepareProject(gradleVersion) {
+            chooseCompilerVersion(TestVersions.Kotlin.STABLE_RELEASE)
+            build(printClasspathTaskName) {
+                assertCompilerVersion(TestVersions.Kotlin.STABLE_RELEASE)
+            }
+        }
+    }
+
+    @GradleTest
+    @DisplayName("Compiler version may be specified via the kotlin extension multiple times")
+    fun compilerVersionMayBeChangedMultipleTimes(gradleVersion: GradleVersion) {
+        prepareProject(gradleVersion) {
+            chooseCompilerVersion(buildOptions.kotlinVersion)
+            chooseCompilerVersion(TestVersions.Kotlin.STABLE_RELEASE)
+            build(printClasspathTaskName) {
+                assertCompilerVersion(TestVersions.Kotlin.STABLE_RELEASE)
+            }
+        }
+    }
+
+    @GradleTest
+    @DisplayName("Manual adding dependencies to the classpath configuration does not change kotlin version")
+    fun manualAdding(gradleVersion: GradleVersion) {
+        prepareProject(gradleVersion) {
+            buildGradle.append(
+                //language=Gradle
+                """
+                dependencies {
+                    $KOTLIN_BUILD_TOOLS_API_CLASSPATH_CONFIGURATION_NAME("org.jetbrains.kotlin:kotlin-compiler-embeddable:${TestVersions.Kotlin.STABLE_RELEASE}")
+                }
+                """.trimIndent()
+            )
+            build(printClasspathTaskName) {
+                assertCompilerVersion(buildOptions.kotlinVersion)
+            }
+        }
+    }
+
+    private val printClasspathTaskName = "printBuildToolsApiClasspath"
+
+    private fun BuildResult.assertCompilerVersion(version: String) {
+        val compilerDependencies = extractClasspathFromLogs()
+            .filter { "kotlin-compiler-embeddable" in it }
+            .toList()
+        assert(compilerDependencies.isNotEmpty()) {
+            "Expected dependencies to contain `kotlin-compiler-embeddable`"
+        }
+        val nonMatchingVersionDependencies = compilerDependencies
+            .filter { !it.endsWith("$version.jar") }
+        assert(nonMatchingVersionDependencies.isEmpty()) {
+            "Kotlin dependencies expected to be of version '$version', the following dependencies do not pass the check: $nonMatchingVersionDependencies"
+        }
+    }
+
+    private val classpathLogLinePrefix = "kotlin classpath: "
+
+    private fun BuildResult.extractClasspathFromLogs() = output.lineSequence()
+        .filter { it.startsWith(classpathLogLinePrefix) }
+        .map { it.replaceFirst(classpathLogLinePrefix, "") }
+
+    private fun prepareProject(gradleVersion: GradleVersion, test: TestProject.() -> Unit = {}) {
+        project("simpleProject", gradleVersion) {
+            buildGradle.append(
+                //language=Gradle
+                """
+                tasks.register("$printClasspathTaskName") {
+                    FileCollection classpath = configurations.$KOTLIN_BUILD_TOOLS_API_CLASSPATH_CONFIGURATION_NAME
+                    doFirst {
+                        classpath.forEach {
+                            println("$classpathLogLinePrefix" + it)
+                        }
+                    }
+                }
+                """.trimIndent()
+            )
+            test()
+        }
+    }
+}

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

@@ -6,6 +6,7 @@
 package org.jetbrains.kotlin.gradle.internals
 
 import org.jetbrains.kotlin.compilerRunner.asFinishLogMessage
+import org.jetbrains.kotlin.gradle.plugin.BUILD_TOOLS_API_CLASSPATH_CONFIGURATION_NAME
 import org.jetbrains.kotlin.gradle.plugin.PropertiesProvider.PropertyNames.KOTLIN_NATIVE_IGNORE_DISABLED_TARGETS
 import org.jetbrains.kotlin.gradle.plugin.PropertiesProvider.PropertyNames.KOTLIN_INTERNAL_DIAGNOSTICS_USE_PARSABLE_FORMATTING
 import org.jetbrains.kotlin.gradle.plugin.PropertiesProvider.PropertyNames.KOTLIN_INTERNAL_DIAGNOSTICS_SHOW_STACKTRACE
@@ -35,3 +36,4 @@ val KOTLIN_INTERNAL_DIAGNOSTICS_USE_PARSABLE_FORMATTING = KOTLIN_INTERNAL_DIAGNO
 val KOTLIN_INTERNAL_DIAGNOSTICS_SHOW_STACKTRACE = KOTLIN_INTERNAL_DIAGNOSTICS_SHOW_STACKTRACE
 val KOTLIN_DIAGNOSTIC_STACKTRACE_START = DIAGNOSTIC_STACKTRACE_START
 val KOTLIN_DIAGNOSTIC_STACKTRACE_END_SEPARATOR = DIAGNOSTIC_STACKTRACE_END_SEPARATOR
+val KOTLIN_BUILD_TOOLS_API_CLASSPATH_CONFIGURATION_NAME = BUILD_TOOLS_API_CLASSPATH_CONFIGURATION_NAME