[Gradle] Add integration test checking 'kotlin.user.home' is possible to change

^KT-58223 In Progress

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

@@ -280,10 +280,7 @@ class BuildReportsIT : KGPBaseTest() {
         ) {
 
             val lookupsTab = projectPath.resolve("build/kotlin/compileKotlin/cacheable/caches-jvm/lookups/lookups.tab")
-            fun kotlinErrorPath() = tempDir
-                .resolve("projects-1")
-                .findInPath("errors")
-                ?: throw IllegalStateException("Could not find global Kotlin errors directory!")
+            fun kotlinErrorPath() = tempDir.inProjectsPersistentCache("errors")
 
             buildGradle.appendText(
                 """
@@ -334,10 +331,7 @@ class BuildReportsIT : KGPBaseTest() {
             gradleVersion = gradleVersion,
             buildOptions = defaultBuildOptions.copy(kotlinUserHome = tempDir)
         ) {
-            fun kotlinErrorPath() = tempDir
-                .resolve("projects-1")
-                .findInPath("errors")
-                ?: throw IllegalStateException("Could not find global Kotlin errors directory!")
+            fun kotlinErrorPath() = tempDir.inProjectsPersistentCache("errors")
 
             build("compileKotlin", buildOptions = defaultBuildOptions.copy(logLevel = LogLevel.DEBUG)) {
                 assertOutputDoesNotContain("errors were stored into file")

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

@@ -176,9 +176,7 @@ open class CommonizerIT : KGPBaseTest() {
 
             configureCommonizerTargets()
 
-            fun expectedOutputDirectoryForIde(): Path = tempDir
-                .resolve("projects-1")
-                .findInPath("commonizer") ?: throw IllegalStateException("Failed to find 'commonizer' directory!")
+            fun expectedOutputDirectoryForIde(): Path = tempDir.inProjectsPersistentCache("commonizer")
 
             val expectedOutputDirectoryForBuild = projectPath.resolve("build/classes/kotlin/commonizer")
 
@@ -551,9 +549,7 @@ open class CommonizerIT : KGPBaseTest() {
 
             configureCommonizerTargets()
 
-            fun expectedOutputDirectoryForIde(): Path = tempDir
-                .resolve("projects-1")
-                .findInPath("commonizer") ?: throw IllegalStateException("Failed to find 'commonizer' directory!")
+            fun expectedOutputDirectoryForIde(): Path = tempDir.inProjectsPersistentCache("commonizer")
 
             build(":copyCommonizeCInteropForIde") {
                 assertTasksExecuted(":cinteropCurlTargetB")

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

@@ -6,8 +6,11 @@ import org.gradle.util.GradleVersion
 import org.jetbrains.kotlin.gradle.tasks.KotlinCompilerExecutionStrategy
 import org.jetbrains.kotlin.gradle.testbase.*
 import org.junit.jupiter.api.DisplayName
+import org.junit.jupiter.api.io.TempDir
+import java.nio.file.Path
 import java.util.zip.ZipFile
 import kotlin.io.path.*
+import kotlin.test.assertEquals
 
 @JvmGradlePluginTests
 @DisplayName("KGP simple tests")
@@ -289,4 +292,35 @@ class SimpleKotlinGradleIT : KGPBaseTest() {
             }
         }
     }
+
+    @DisplayName("Possible to override kotlin.user.home location")
+    @GradleTest
+    fun overrideKotlinUserHome(
+        gradleVersion: GradleVersion,
+        @TempDir tempDir: Path,
+    ) {
+        project(
+            projectName = "simpleProject",
+            gradleVersion = gradleVersion,
+            buildOptions = defaultBuildOptions.copy(kotlinUserHome = null)
+        ) {
+            gradleProperties.appendText(
+                """
+                |
+                |kotlin.user.home=${tempDir.absolutePathString().normalizePath()}
+                """.trimMargin()
+            )
+
+            build("compileKotlin") {
+                assertTasksExecuted(":compileKotlin")
+
+                val baseProjectsDir = tempDir.resolve("projects-1")
+                assertDirectoryExists(baseProjectsDir)
+                val projectsDirs = baseProjectsDir.listDirectoryEntries()
+                assertEquals(1, projectsDirs.size, message = "More then 1 child! Actual content ${projectsDirs.joinToString { it.pathString }}")
+                assertDirectoryExists(projectsDirs.first().resolve("sessions"))
+                assertDirectoryExists(projectsDirs.first().resolve("errors"))
+            }
+        }
+    }
 }

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

@@ -120,3 +120,21 @@ fun Path.getSingleFileInDir(relativePath: String): Path {
     }
 }
 
+/**
+ * Get a path for per-project persistent cache directory from this base persistent cache directory.
+ */
+fun Path.projectsPersistentCache() = resolve("projects-1")
+
+/**
+ * Searches for the specified directory in the projects persistent cache.
+ *
+ * @param directoryName The name of the directory to search for.
+ * @return The path of the directory if found.
+ *
+ * @throws IllegalStateException if the directory does not exist in the projects cache. Usually they are populated after some build.
+ */
+fun Path.inProjectsPersistentCache(
+    directoryName: String
+) = projectsPersistentCache().findInPath(directoryName)
+    ?: throw IllegalStateException("$directoryName does not exist in the projects cache under ${this.absolutePathString()}")
+