From d1e59ec070d523b1f2d6b14b106ee7028c82f2aa Mon Sep 17 00:00:00 2001
From: Li Haoyi <haoyi.sg@gmail.com>
Date: Tue, 7 Dec 2021 12:53:25 +0800
Subject: [PATCH 1/2] .

---
 os/src-jvm/ResourcePath.scala |  2 +-
 os/src/Path.scala             | 21 ++++++++++++++-------
 os/test/src/PathTests.scala   |  7 +++++++
 3 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/os/src-jvm/ResourcePath.scala b/os/src-jvm/ResourcePath.scala
index 6e7160e2..cb97dde2 100644
--- a/os/src-jvm/ResourcePath.scala
+++ b/os/src-jvm/ResourcePath.scala
@@ -23,7 +23,7 @@ class ResourcePath private[os](val resRoot: ResourceRoot, segments0: Array[Strin
   def toSource = new Source.WritableSource(getInputStream)
   val segments: IndexedSeq[String] = segments0
   type ThisType = ResourcePath
-  def last = segments0.last
+  def lastOpt = segments0.lastOption
   override def toString = resRoot.errorName + "/" + segments0.mkString("/")
   protected[this] def make(p: Seq[String], ups: Int) = {
     if (ups > 0){
diff --git a/os/src/Path.scala b/os/src/Path.scala
index 10717e0b..6e573d97 100644
--- a/os/src/Path.scala
+++ b/os/src/Path.scala
@@ -182,9 +182,14 @@ trait BasePathImpl extends BasePath{
   def /(chunk: PathChunk): ThisType
 
   def ext = {
-    val li = last.lastIndexOf('.')
-    if (li == -1) ""
-    else last.slice(li+1, last.length)
+    lastOpt match{
+      case None => ""
+      case Some(lastSegment) =>
+        val li = lastSegment.lastIndexOf('.')
+        if (li == -1) ""
+        else last.slice(li+1, last.length)
+    }
+
   }
 
   override def baseName: String = {
@@ -193,7 +198,9 @@ trait BasePathImpl extends BasePath{
     else last.slice(0, li)
   }
 
-  def last: String
+  def last: String = lastOpt.getOrElse("empty path has no last segment")
+
+  def lastOpt: Option[String]
 }
 
 object PathError{
@@ -239,7 +246,7 @@ object FilePath {
   */
 class RelPath private[os](segments0: Array[String], val ups: Int)
   extends FilePath with BasePathImpl with SegmentedPath {
-  def last = segments.last
+  def lastOpt = segments.lastOption
   val segments: IndexedSeq[String] = segments0
   type ThisType = RelPath
   require(ups >= 0)
@@ -305,7 +312,7 @@ object RelPath {
   */
 class SubPath private[os](val segments0: Array[String])
   extends FilePath with BasePathImpl with SegmentedPath {
-  def last = segments.last
+  def lastOpt = segments.lastOption
   val segments: IndexedSeq[String] = segments0
   type ThisType = SubPath
   protected[this] def make(p: Seq[String], ups: Int) = {
@@ -433,7 +440,7 @@ class Path private[os](val wrapped: java.nio.file.Path)
   def segmentCount = wrapped.getNameCount
   type ThisType = Path
 
-  def last = wrapped.getFileName.toString
+  def lastOpt = Option(wrapped.getFileName).map(_.toString)
 
   def /(chunk: PathChunk): ThisType = {
     if (chunk.ups > wrapped.getNameCount) throw PathError.AbsolutePathOutsideRoot
diff --git a/os/test/src/PathTests.scala b/os/test/src/PathTests.scala
index 37c2e363..5908edb5 100644
--- a/os/test/src/PathTests.scala
+++ b/os/test/src/PathTests.scala
@@ -47,6 +47,13 @@ object PathTests extends TestSuite{
           assert((base / "baseOnly").ext == "")
           assert((base / "baseOnly.").ext == "")
         }
+
+        test("emptyExt"){
+          os.root.ext ==> ""
+          os.rel.ext ==> ""
+          os.sub.ext ==> ""
+          os.up.ext ==> ""
+        }
       }
 
       test("RelPath"){

From ca3aa0c15df9a0928c4e622ecee91f4462188f5c Mon Sep 17 00:00:00 2001
From: Li Haoyi <haoyi.sg@gmail.com>
Date: Wed, 8 Dec 2021 18:36:30 +0800
Subject: [PATCH 2/2] .

---
 os/src/Path.scala           |  5 ++++-
 os/test/src/PathTests.scala | 11 +++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/os/src/Path.scala b/os/src/Path.scala
index 6e573d97..b34a3da6 100644
--- a/os/src/Path.scala
+++ b/os/src/Path.scala
@@ -198,7 +198,7 @@ trait BasePathImpl extends BasePath{
     else last.slice(0, li)
   }
 
-  def last: String = lastOpt.getOrElse("empty path has no last segment")
+  def last: String = lastOpt.getOrElse(throw PathError.LastOnEmptyPath())
 
   def lastOpt: Option[String]
 }
@@ -215,6 +215,9 @@ object PathError{
 
   case class NoRelativePath(src: RelPath, base: RelPath)
     extends IAE(s"Can't relativize relative paths $src from $base")
+
+  case class LastOnEmptyPath()
+    extends IAE("empty path has no last segment")
 }
 
 /**
diff --git a/os/test/src/PathTests.scala b/os/test/src/PathTests.scala
index 5908edb5..d96a664d 100644
--- a/os/test/src/PathTests.scala
+++ b/os/test/src/PathTests.scala
@@ -54,6 +54,17 @@ object PathTests extends TestSuite{
           os.sub.ext ==> ""
           os.up.ext ==> ""
         }
+
+        test("emptyLast"){
+          intercept[PathError.LastOnEmptyPath](os.root.last).getMessage ==>
+            "empty path has no last segment"
+          intercept[PathError.LastOnEmptyPath](os.rel.last).getMessage ==>
+            "empty path has no last segment"
+          intercept[PathError.LastOnEmptyPath](os.sub.last).getMessage ==>
+            "empty path has no last segment"
+          intercept[PathError.LastOnEmptyPath](os.up.last).getMessage ==>
+            "empty path has no last segment"
+        }
       }
 
       test("RelPath"){