From 4f3999c20f26f27c6b3513884d90e783352d1f8e Mon Sep 17 00:00:00 2001
From: Chris Beck <5683852+cbeck88@users.noreply.github.com>
Date: Sat, 22 Jun 2024 15:31:22 -0600
Subject: [PATCH] Add `Router::has_routes` (#2790)

---
 axum/CHANGELOG.md                    | 2 ++
 axum/src/docs/routing/route_layer.md | 4 ++++
 axum/src/routing/mod.rs              | 5 +++++
 axum/src/routing/path_router.rs      | 4 ++++
 4 files changed, 15 insertions(+)

diff --git a/axum/CHANGELOG.md b/axum/CHANGELOG.md
index 14b52f1f..13730f5b 100644
--- a/axum/CHANGELOG.md
+++ b/axum/CHANGELOG.md
@@ -9,8 +9,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - **change:** Avoid cloning `Arc` during deserialization of `Path`
 - **added:** `axum::serve::Serve::tcp_nodelay` and `axum::serve::WithGracefulShutdown::tcp_nodelay` ([#2653])
+- **added:** `Router::has_routes` function ([#2790])
 
 [#2653]: https://github.com/tokio-rs/axum/pull/2653
+[#2790]: https://github.com/tokio-rs/axum/pull/2790
 
 # 0.7.5 (24. March, 2024)
 
diff --git a/axum/src/docs/routing/route_layer.md b/axum/src/docs/routing/route_layer.md
index bc7b2197..9cce3ea7 100644
--- a/axum/src/docs/routing/route_layer.md
+++ b/axum/src/docs/routing/route_layer.md
@@ -11,6 +11,10 @@ the request matches a route. This is useful for middleware that return early
 (such as authorization) which might otherwise convert a `404 Not Found` into a
 `401 Unauthorized`.
 
+This function will panic if no routes have been declared yet on the router,
+since the new layer will have no effect, and this is typically a bug.
+In generic code, you can test if that is the case first, by calling [`Router::has_routes`].
+
 # Example
 
 ```rust
diff --git a/axum/src/routing/mod.rs b/axum/src/routing/mod.rs
index 47b85474..dc6ca815 100644
--- a/axum/src/routing/mod.rs
+++ b/axum/src/routing/mod.rs
@@ -307,6 +307,11 @@ where
         })
     }
 
+    /// True if the router currently has at least one route added.
+    pub fn has_routes(&self) -> bool {
+        self.inner.path_router.has_routes()
+    }
+
     #[track_caller]
     #[doc = include_str!("../docs/routing/fallback.md")]
     pub fn fallback<H, T>(self, handler: H) -> Self
diff --git a/axum/src/routing/path_router.rs b/axum/src/routing/path_router.rs
index 345d6671..e132f1dc 100644
--- a/axum/src/routing/path_router.rs
+++ b/axum/src/routing/path_router.rs
@@ -290,6 +290,10 @@ where
         }
     }
 
+    pub(super) fn has_routes(&self) -> bool {
+        !self.routes.is_empty()
+    }
+
     pub(super) fn with_state<S2>(self, state: S) -> PathRouter<S2, IS_FALLBACK> {
         let routes = self
             .routes