Compare root of FilePathComponents according to case-sensitivity rules of current file system.

libraries/stdlib/src/kotlin/io/files/FilePathComponents.kt

@@ -91,6 +91,11 @@ public data class FilePathComponents(public val rootName: String, public val fil
      */
     public fun size(): Int = fileList.size
 
+    /**
+     * [File] representing root of the path (for example, `/` or `C:` or empty for relative paths).
+     */
+    public val root: File = File(rootName)
+
     /**
      * Returns a sub-path of the path, starting with the directory at the specified [beginIndex] and up
      * to the specified [endIndex].

libraries/stdlib/src/kotlin/io/files/Utils.kt

@@ -131,7 +131,7 @@ private fun File.relativeToOrNull(base: File): String? {
     // Check roots
     val thisComponents = this.filePathComponents().normalize()
     val baseComponents = base.filePathComponents().normalize()
-    if (thisComponents.rootName != baseComponents.rootName) {
+    if (thisComponents.root != baseComponents.root) {
         return null
     }
 
@@ -333,7 +333,7 @@ public fun File.listFiles(filter: (file: File) -> Boolean): Array<File>? = listF
 public fun File.startsWith(other: File): Boolean {
     val components = filePathComponents()
     val otherComponents = other.filePathComponents()
-    if (components.rootName != otherComponents.rootName && otherComponents.rootName != "")
+    if (components.root != otherComponents.root && otherComponents.rootName != "")
         return false
     return if (components.size() < otherComponents.size()) false
     else components.fileList.subList(0, otherComponents.size()).equals(otherComponents.fileList)
@@ -360,7 +360,7 @@ public fun File.startsWith(other: String): Boolean = startsWith(File(other))
 public fun File.endsWith(other: File): Boolean {
     val components = filePathComponents()
     val otherComponents = other.filePathComponents()
-    if (components.rootName != otherComponents.rootName && otherComponents.rootName != "")
+    if (components.root != otherComponents.root && otherComponents.rootName != "")
         return false
     val shift = components.size() - otherComponents.size()
     return if (shift < 0) false
@@ -436,8 +436,7 @@ public fun File.resolve(relative: String): File = resolve(File(relative))
 public fun File.resolveSibling(relative: File): File {
     val components = filePathComponents()
     val parentSubPath = if (components.size() == 0) File("..") else components.subPath(0, components.size() - 1)
-    val rootName = components.rootName
+    return components.root.resolve(parentSubPath).resolve(relative)
-    return File(rootName).resolve(parentSubPath).resolve(relative)
 }
 
 /**

libraries/stdlib/test/io/Files.kt

@@ -7,6 +7,8 @@ import kotlin.test.*
 
 class FilesTest {
 
+    private val isCaseInsensitiveFileSystem = File("C:/") == File("c:/")
+
     @test fun testPath() {
         val fileSuf = System.currentTimeMillis().toString()
         val file1 = createTempFile("temp", fileSuf)
@@ -100,6 +102,10 @@ class FilesTest {
         assertEquals("..", file6.relativeTo(file7))
         assertEquals("Documents", file7.relativeTo(file6))
 
+        if (isCaseInsensitiveFileSystem) {
+            assertEquals("bar", File("C:/bar").relativeTo(File("c:/")))
+        }
+
         val file8 = File("""\\my.host\home/user/documents/vip""")
         val file9 = File("""\\my.host\home/other/images/nice""")
 
@@ -215,6 +221,9 @@ class FilesTest {
         assertTrue(File("C:\\Users\\Me\\Temp\\Game").startsWith("C:\\Users\\Me"))
         assertFalse(File("C:\\Users\\Me\\Temp\\Game").startsWith("C:\\Users\\He"))
         assertTrue(File("C:\\Users\\Me").startsWith("C:\\"))
+        if (isCaseInsensitiveFileSystem) {
+            assertTrue(File("C:\\Users\\Me").startsWith("c:\\"))
+        }
     }
 
     @test fun endsWith() {
@@ -224,6 +233,9 @@ class FilesTest {
         assertTrue(File("/foo/bar/gav/bar").endsWith("/gav/bar"))
         assertFalse(File("/foo/bar/gav").endsWith("/bar"))
         assertFalse(File("foo/bar").endsWith("/bar"))
+        if (isCaseInsensitiveFileSystem) {
+            assertTrue(File("/foo/bar").endsWith("Bar"))
+        }
     }
 
     @test fun subPath() {