From e64e0fc00802f87d3c2bde04ed020e3590944754 Mon Sep 17 00:00:00 2001
From: Tim Nieradzik <tim@sparse.tech>
Date: Mon, 8 Jul 2019 16:44:10 +0300
Subject: [PATCH] Route: Fix parsing of optional path elements

---
 shared/src/main/scala/trail/Route.scala           |  2 +-
 shared/src/test/scala/trail/RouteParseTests.scala | 13 +++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/shared/src/main/scala/trail/Route.scala b/shared/src/main/scala/trail/Route.scala
index 0c7d4bd..036e71d 100644
--- a/shared/src/main/scala/trail/Route.scala
+++ b/shared/src/main/scala/trail/Route.scala
@@ -57,7 +57,7 @@ object Route {
     override def url(value: T): String = arg.codec.encode(value).getOrElse("")
     override def parseInternal(path: Path): Option[(T, Path)] = {
       val untilSlash = path.path.takeWhile(_ != '/')
-      arg.codec.decode(Some(untilSlash))
+      arg.codec.decode(if (untilSlash.isEmpty) None else Some(untilSlash))
         .map(value => (value, path.copy(path =
           path.path.drop(untilSlash.length + 1))))
     }
diff --git a/shared/src/test/scala/trail/RouteParseTests.scala b/shared/src/test/scala/trail/RouteParseTests.scala
index ea17d32..c306565 100644
--- a/shared/src/test/scala/trail/RouteParseTests.scala
+++ b/shared/src/test/scala/trail/RouteParseTests.scala
@@ -38,6 +38,19 @@ class RouteParseTests extends FunSpec with Matchers {
     assert(parsed === Some((("bob", true), 42)))
   }
 
+  it("Route with optional path element can be parsed") {
+    val disk = Root / Arg[Option[Long]]
+    assert(disk.parse("/").contains(None))
+    assert(disk.parse("/42").contains(Some(42L)))
+  }
+
+  it("Route with optional path element can be parsed (2)") {
+    val disk = Root / "disk" / Arg[Option[Long]]
+    assert(disk.parse("/disk").contains(None))
+    assert(disk.parse("/disk/").contains(None))
+    assert(disk.parse("/disk/42").contains(Some(42L)))
+  }
+
   it("Route can be parsed from string") {
     val userInfo = Root / "user" / Arg[String] / Arg[Boolean]