[IC] Handle custom source set located outside project directory

To support build cache relocatability, we need to convert absolute paths
into relative paths before storing them in IC caches.

Before this commit, we computed relative paths based on the (root)
project directory and FAIL if some source files are located outside the
project directory.

With this commit, we will NOT FAIL in that case. This means relative
paths may start with "../". It's not "clean", but it can work.

Test: New test in BuildCacheRelocationIT
^KT-61852 Fixed

build-common/src/org/jetbrains/kotlin/incremental/storage/RelocatableFileToPathConverter.kt

@@ -16,12 +16,9 @@ import java.io.File
  */
 class RelocatableFileToPathConverter(private val baseDir: File) : FileToPathConverter {
 
-    private val unixStyleBaseDirPathPrefix = "${baseDir.invariantSeparatorsPath}/"
-
     override fun toPath(file: File): String {
-        check(file.invariantSeparatorsPath.startsWith(unixStyleBaseDirPathPrefix)) {
-            "The given file '${file.path}' is located outside the base directory '${baseDir.path}'"
-        }
+        // Note: If the given file is located outside `baseDir`, the relative path will start with "../". It's not "clean", but it can work.
+        // TODO: Re-design the code such that `baseDir` always contains the given file (also add a precondition check here).
         return file.relativeTo(baseDir).invariantSeparatorsPath
     }
 

build-common/test/org/jetbrains/kotlin/incremental/storage/RelocatableFileToPathConverterTest.kt

@@ -5,34 +5,43 @@
 
 package org.jetbrains.kotlin.incremental.storage
 
-import org.jetbrains.kotlin.TestWithWorkingDir
+import org.junit.Assert.assertEquals
+import org.junit.Before
+import org.junit.Rule
 import org.junit.Test
-import kotlin.test.assertFailsWith
+import org.junit.rules.TemporaryFolder
+import java.io.File
 
-class RelocatableFileToPathConverterTest : TestWithWorkingDir() {
+class RelocatableFileToPathConverterTest {
 
+    @get:Rule
+    val tmpDir = TemporaryFolder()
+
+    private lateinit var baseDir: File
     private lateinit var pathConverter: RelocatableFileToPathConverter
 
-    override fun setUp() {
-        super.setUp()
-        pathConverter = RelocatableFileToPathConverter(workingDir)
+    @Before
+    fun setUp() {
+        baseDir = tmpDir.newFolder("baseDir")
+        pathConverter = RelocatableFileToPathConverter(baseDir)
     }
 
     @Test
     fun testToPath() {
-        assertEquals("com/example/Foo.kt", pathConverter.toPath(workingDir.resolve("com/example/Foo.kt")))
-    }
-
-    @Test
-    fun testToPathFails() {
-        assertFailsWith(IllegalStateException::class) {
-            pathConverter.toPath(workingDir.resolve("../outsideWorkingDir/com/example/Foo.kt").normalize())
-        }
+        assertEquals("com/example/Foo.kt", pathConverter.toPath(baseDir.resolve("com/example/Foo.kt")))
     }
 
     @Test
     fun testToFile() {
-        assertEquals(workingDir.resolve("com/example/Foo.kt"), pathConverter.toFile("com/example/Foo.kt"))
+        assertEquals(baseDir.resolve("com/example/Foo.kt"), pathConverter.toFile("com/example/Foo.kt"))
+    }
+
+    @Test
+    fun testFileOutsideBaseDirectory() {
+        val fileOutsideBaseDir = baseDir.resolve("../outsideBaseDir/com/example/Foo.kt").normalize()
+
+        assertEquals("../outsideBaseDir/com/example/Foo.kt", pathConverter.toPath(fileOutsideBaseDir))
+        assertEquals(fileOutsideBaseDir, pathConverter.toFile("../outsideBaseDir/com/example/Foo.kt"))
     }
 
 }