Simplify and optimize router.

This surfaced a dormant concurrency related issue. Prior to this commit,
the router used `routed_segments()` to retrieve the path segments of the
request. This was okay as there was no route in the request, and matched
segments were retrieved eagerly.

This commit makes segment matching lazy, so no matching occurs if
unnecessary. Between two matches, a `route` is atomically set of
`Request`. This is now visible in `routed_segments()`, which should not
have considered the current route in the first place. This was fixed.

core/lib/src/rocket.rs

@@ -525,8 +525,10 @@ impl Rocket {
     ///     * there were no fairing failures
     ///     * a secret key, if needed, is securely configured
     pub(crate) async fn prelaunch_check(&mut self) -> Result<(), Error> {
-        if let Err(e) = self.router.collisions() {
-            return Err(Error::new(ErrorKind::Collision(e)));
+        let collisions: Vec<_> = self.router.collisions().collect();
+        if !collisions.is_empty() {
+            let owned = collisions.into_iter().map(|(a, b)| (a.clone(), b.clone()));
+            return Err(Error::new(ErrorKind::Collision(owned.collect())));
         }
 
         if let Some(failures) = self.fairings.failures() {

core/lib/src/router/collider.rs

@@ -71,7 +71,7 @@ fn paths_collide(route: &Route, other: &Route) -> bool {
 
 fn paths_match(route: &Route, req: &Request<'_>) -> bool {
     let route_segments = &route.uri.metadata.path_segs;
-    let req_segments = req.routed_segments(0..);
+    let req_segments = req.uri().path_segments();
     if route_segments.len() > req_segments.len() + 1 {
         return false;
     }

core/lib/src/router/mod.rs

@@ -7,7 +7,6 @@ use std::collections::HashMap;
 
 use crate::request::Request;
 use crate::http::Method;
-use crate::handler::dummy;
 
 pub use self::route::Route;
 pub use self::uri::RouteUri;
@@ -34,64 +33,33 @@ impl Router {
         entries.insert(i, route);
     }
 
-    pub fn route<'b>(&'b self, req: &Request<'_>) -> Vec<&'b Route> {
+    pub fn route<'r, 'a: 'r>(&'a self, req: &'r Request<'r>) -> impl Iterator<Item = &'a Route> + 'r {
         // Note that routes are presorted by rank on each `add`.
-        let matches = self.routes.get(&req.method()).map_or(vec![], |routes| {
-            routes.iter()
-                .filter(|r| r.matches(req))
-                .collect()
-        });
-
-        trace_!("Routing the request: {}", req);
-        trace_!("All matches: {:?}", matches);
-        matches
+        self.routes.get(&req.method())
+            .into_iter()
+            .flat_map(move |routes| routes.iter().filter(move |r| r.matches(req)))
     }
 
-    pub(crate) fn collisions(&mut self) -> Result<(), Vec<(Route, Route)>> {
-        let mut collisions = vec![];
-        for routes in self.routes.values_mut() {
-            for i in 0..routes.len() {
-                let (left, right) = routes.split_at_mut(i);
-                for a_route in left.iter_mut() {
-                    for b_route in right.iter_mut() {
-                        if a_route.collides_with(b_route) {
-                            let dummy_a = Route::new(Method::Get, "/", dummy);
-                            let a = std::mem::replace(a_route, dummy_a);
-                            let dummy_b = Route::new(Method::Get, "/", dummy);
-                            let b = std::mem::replace(b_route, dummy_b);
-                            collisions.push((a, b));
-                        }
-                    }
-                }
-            }
-        }
-
-        if collisions.is_empty() {
-            Ok(())
-        } else {
-            Err(collisions)
-        }
+    pub(crate) fn collisions(&self) -> impl Iterator<Item = (&Route, &Route)> {
+        let all_routes = self.routes.values().flat_map(|v| v.iter());
+        all_routes.clone().enumerate()
+            .flat_map(move |(i, a)| {
+                all_routes.clone()
+                    .skip(i + 1)
+                    .filter(move |b| b.collides_with(a))
+                    .map(move |b| (a, b))
+            })
     }
 
     #[inline]
-    pub fn routes<'a>(&'a self) -> impl Iterator<Item=&'a Route> + 'a {
+    pub fn routes(&self) -> impl Iterator<Item = &Route> {
         self.routes.values().flat_map(|v| v.iter())
     }
 
     // This is slow. Don't expose this publicly; only for tests.
     #[cfg(test)]
     fn has_collisions(&self) -> bool {
-        for routes in self.routes.values() {
-            for (i, a_route) in routes.iter().enumerate() {
-                for b_route in routes.iter().skip(i + 1) {
-                    if a_route.collides_with(b_route) {
-                        return true;
-                    }
-                }
-            }
-        }
-
-        false
+        self.collisions().next().is_some()
     }
 }
 
@@ -266,21 +234,17 @@ mod test {
         assert!(!default_rank_route_collisions(&["/hi?<c>", "/hi?c"]));
     }
 
-    fn route<'a>(router: &'a Router, method: Method, uri: &str) -> Option<&'a Route> {
+    fn route<'a>(router: &'a Router, method: Method, uri: &'a str) -> Option<&'a Route> {
         let rocket = Rocket::custom(Config::default());
         let request = Request::new(&rocket, method, Origin::parse(uri).unwrap());
-        let matches = router.route(&request);
-        if matches.len() > 0 {
-            Some(matches[0])
-        } else {
-            None
-        }
+        let route = router.route(&request).next();
+        route
     }
 
-    fn matches<'a>(router: &'a Router, method: Method, uri: &str) -> Vec<&'a Route> {
+    fn matches<'a>(router: &'a Router, method: Method, uri: &'a str) -> Vec<&'a Route> {
         let rocket = Rocket::custom(Config::default());
         let request = Request::new(&rocket, method, Origin::parse(uri).unwrap());
-        router.route(&request)
+        router.route(&request).collect()
     }
 
     #[test]

core/lib/src/server.rs

@@ -286,8 +286,7 @@ impl Rocket {
         mut data: Data,
     ) -> handler::Outcome<'r> {
         // Go through the list of matching routes until we fail or succeed.
-        let matches = self.router.route(request);
-        for route in matches {
+        for route in self.router.route(request) {
             // Retrieve and set the requests parameters.
             info_!("Matched: {}", route);
             request.set_route(route);