IO.relativize is broken when base contains ".."

[eed3si9n]

The inconsisnt behavior in JDK 11 reported in #85 exposed that IO.relativize is currently incorrect.

steps

Given that the base directory is /tmp/io-relativize/inside-dir/.. and that the target to be relativized is /tmp/io-relativize/meh.file, IOSpec states

IO.relativize(relativeRootDir, nestedFile).map(file) shouldBe Some(file("../../meh.file"))

problem

Some(file("../../meh.file")) is incorrect.

expectation

Some("meh.file")

notes

  def relativize(base: File, file: File): Option[String] = {
    val basePath = (if (base.isAbsolute) base else base.getCanonicalFile).toPath
    val filePath = (if (file.isAbsolute) file else file.getCanonicalFile).toPath
    if ((filePath startsWith basePath) || (filePath.normalize() startsWith basePath.normalize())) {
      val relativePath = catching(classOf[IllegalArgumentException]) opt (basePath relativize filePath)
      relativePath map (_.toString)
    } else None
  }

https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/io/File.html#isAbsolute:

On UNIX systems, a pathname is absolute if its prefix is "/".

https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/io/File.html#getCanonicalPath():

This typically involves removing redundant names such as "." and ".." from the pathname, resolving symbolic links (on UNIX platforms)

https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/nio/file/Path.html#normalize()

Returns a path that is this path with redundant name elements eliminated.

See also #175