[routing] Add special consideration for root path (javalin#1808)

Refs javalin#1803

Author: Playacem

javalin/src/main/java/io/javalin/routing/PathParser.kt

@@ -30,13 +30,19 @@ class PathParser(private val rawPath: String, routingConfig: RoutingConfig) {
         // when multiple slashes are accepted we have to allow 0-n slashes when using ignoreTrailingSlashes
         // otherwise we also have to allow multiple slashes when only one slash is specified
         when {
+            // the root path is special: we already add a leading slash during regex construction,
+            // so we do not need to add an extra slash with the suffix
+            rawPath == "/" -> ""
             routingConfig.ignoreTrailingSlashes -> "/*"
             rawPath.endsWith("/") -> "/+"
             else -> ""
         }
     } else {
         // if ignoreTrailingSlashes config is set we keep /?, else we use the true path trailing slash : present or absent
         when {
+            // the root path is special: we already add a leading slash during regex construction,
+            // so we do not need to add an extra slash with the suffix
+            rawPath == "/" -> ""
             routingConfig.ignoreTrailingSlashes -> "/?"
             rawPath.endsWith("/") -> "/"
             else -> ""

javalin/src/test/java/io/javalin/TestRouting.kt

@@ -283,4 +283,26 @@ class TestRouting {
             }
         }
     }
+
+    @Test
+    fun `root path works with ignoreTrailingSlashes set to false`() = TestUtil.test(Javalin.create {
+        it.routing.ignoreTrailingSlashes = false
+    }) { app, http ->
+        app.get("/") { it.result("root") }
+        app.get("/home") { it.result("home") }
+        assertThat(http.getBody("/")).isEqualTo("root")
+        assertThat(http.getBody("/home")).isEqualTo("home")
+    }
+
+    @Test
+    fun `root path works with ApiBuilder and ignoreTrailingSlashes set to false`() = TestUtil.test(Javalin.create {
+        it.routing.ignoreTrailingSlashes = false
+    }) { app, http ->
+        app.routes {
+            get("/") { it.result("root") }
+            get("/home") { it.result("home") }
+        }
+        assertThat(http.getBody("/")).isEqualTo("root")
+        assertThat(http.getBody("/home")).isEqualTo("home")
+    }
 }