+htp #16543 add directives to add or remove trailing slash

akka-http-core/src/main/scala/akka/http/model/Uri.scala

@@ -405,6 +405,16 @@ object Uri {
     def isEmpty: Boolean
     def startsWithSlash: Boolean
     def startsWithSegment: Boolean
+    def endsWithSlash: Boolean = {
+      import Path.{ Empty ⇒ PEmpty, _ }
+      @tailrec def check(path: Path): Boolean = path match {
+        case PEmpty              ⇒ false
+        case Slash(PEmpty)       ⇒ true
+        case Slash(tail)         ⇒ check(tail)
+        case Segment(head, tail) ⇒ check(tail)
+      }
+      check(this)
+    }
     def head: Head
     def tail: Path
     def length: Int

akka-http-core/src/main/scala/akka/http/model/japi/JavaUri.scala

@@ -73,15 +73,8 @@ protected[model] case class JavaUri(uri: model.Uri) extends Uri {
     import model.Uri.Path
     import Path._
 
-    @tailrec def endsWithSlash(path: Path): Boolean = path match {
-      case Empty               ⇒ false
-      case Slash(Empty)        ⇒ true
-      case Slash(tail)         ⇒ endsWithSlash(tail)
-      case Segment(head, tail) ⇒ endsWithSlash(tail)
-    }
-
     val newPath =
-      if (endsWithSlash(u.path)) u.path ++ Path(segment)
+      if (u.path.endsWithSlash) u.path ++ Path(segment)
       else u.path ++ Path./(segment)
 
     u.withPath(newPath)

akka-http-core/src/test/scala/akka/http/model/UriSpec.scala

@@ -241,6 +241,15 @@ class UriSpec extends WordSpec with Matchers {
       Path("/abc/def") startsWith Path("/abc/def") shouldBe true
       Path("/abc/def") startsWith Path("/abc/def/") shouldBe false
     }
+    "support the `endsWithSlash` predicate" in {
+      Empty.endsWithSlash shouldBe false
+      Path./.endsWithSlash shouldBe true
+      Path("abc").endsWithSlash shouldBe false
+      Path("abc/").endsWithSlash shouldBe true
+      Path("/abc").endsWithSlash shouldBe false
+      Path("/abc/def").endsWithSlash shouldBe false
+      Path("/abc/def/").endsWithSlash shouldBe true
+    }
     "support the `dropChars` modifier" in {
       Path./.dropChars(0) shouldEqual Path./
       Path./.dropChars(1) shouldEqual Empty