`Ordering[os.Path]` impl is broken. Trivial fix included.

[ohamel-softwaresecure]

implicit val pathOrdering: Ordering[Path] = new Ordering[Path]{
    def compare(x: Path, y: Path): Int = {
      val xSegCount = x.segmentCount
      val ySegCount = y.segmentCount
      if (xSegCount < ySegCount) -1
      else if (xSegCount > ySegCount) 1
      else if (xSegCount == 0 && ySegCount == 0) 0
      else{
        var xSeg = ""
        var ySeg = ""
        var i = -1                      // FIX: `i = 0`    (`xSegCount != 0` due to checks above)
        do{
          i += 1                        // broke here.@  `i == xSegCount == x.segmentCount` 
          xSeg = x.getSegment(i)        // `x.getSegment(x.segmentCount)`  -> out-of-bounds exception
          ySeg = y.getSegment(i)
                                        // FIX: `i += 1` here
        } while (i < xSegCount && xSeg == ySeg)
        if (i == xSegCount) 0
        else Ordering.String.compare(xSeg, ySeg)
      }
    }
  }

Or for { i <- 0 until xSegCount } { val cmp = x.getSegment(i) compare y.getSegment(i); if (cmp != 0) return cmp }.
EDIT: Or use the java.lang.Comparable of java.nio.file.Path...

[lefou]

Do you have an failing example or test case?

[ohamel-softwaresecure]

#!/usr/local/bin/amm
import ammonite.ops._
import ammonite.ops.ImplicitWd._
def compare(x: os.Path, y: os.Path): Int = {
  val xSegCount = x.segmentCount
  val ySegCount = y.segmentCount
  if (xSegCount < ySegCount) -1
  else if (xSegCount > ySegCount) 1
  else if (xSegCount == 0 && ySegCount == 0) 0
  else{
    var xSeg = ""
    var ySeg = ""
    var i = -1                      // FIX: `i = 0`    (`xSegCount != 0` due to checks above)
    do{
      i += 1                        // broke here.@  `i == xSegCount == x.segmentCount`
      xSeg = x.getSegment(i)        // `x.getSegment(x.segmentCount)`  -> out-of-bounds exception
      ySeg = y.getSegment(i)
                                    // FIX: `i += 1` here
    } while (i < xSegCount && xSeg == ySeg)
    if (i == xSegCount) 0
    else Ordering.String.compare(xSeg, ySeg)
  }
}

import os.Path.pathOrdering // this is annoying to do. :(
val a: os.Path = os.root / "yo" // distinct by identity but value equal
val b: os.Path = os.root / "yo"
println(implicitly[Ordering[os.Path]].compare(a, b))
compare(a, b)

⋊> ~/projects ◦ ./hi.amm                                                                                                                                                                         
Compiling /home/olivier/projects/hi.amm
^[[Ajava.lang.IllegalArgumentException
  sun.nio.fs.UnixPath.getName(UnixPath.java:336)
  sun.nio.fs.UnixPath.getName(UnixPath.java:43)
  os.Path.getSegment(Path.scala:431)
  os.Path$$anon$1.compare(Path.scala:404)
  os.Path$$anon$1.compare(Path.scala:391)
  ammonite.$file.hi$.<clinit>(hi.amm:28)