fix empty route being ignored on insert

When constructing the tree, if the first route is the empty string `""`
the root would be overwritten due to the `self.prefix.is_empty()`.

This adds an additional check to ensure the root is actually `None`
before returning a root node.

Resolves #75

Author: pipex

src/tree.rs

@@ -81,7 +81,7 @@ impl<T> Node<T> {
         self.priority += 1;
 
         // If the tree is empty, insert the root node.
-        if self.prefix.is_empty() && self.children.is_empty() {
+        if self.value.is_none() && self.children.is_empty() {
             let last = self.insert_route(remaining, val)?;
             last.remapping = remapping;
             self.node_type = NodeType::Root;

tests/match.rs

@@ -108,6 +108,16 @@ macro_rules! p {
     };
 }
 
+// https://github.com/ibraheemdev/matchit/issues/75
+#[test]
+fn empty_route() {
+    MatchTest {
+        routes: vec!["", "/foo"],
+        matches: vec![("", "", p! {}), ("/foo", "/foo", p! {})],
+    }
+    .run()
+}
+
 // https://github.com/ibraheemdev/matchit/issues/42
 #[test]
 fn bare_catchall() {