Nested fallback() routes regression with merge() #2072
Description
- I have looked for existing issues (including closed) about this
Bug Report
Version
The error is observed in all versions between 0.6.13 - 0.6.18.
├── axum v0.6.13
│ ├── axum-core v0.3.4
Platform
Linux 5.19.0-45-generic #46~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Wed Jun 7 15:06:04 UTC 20 x86_64 x86_64 x86_64 GNU/Linux
Description
In versions 0.6.13 and beyond a regression with nested routers using fallback() and merge() is observed.
I suspect it relates to the flattening of routes introduced in #1711 .
The snippet below behaves differently between 0.6.12 and 0.6.13 - the nested fallback() is stripped from the flattened router.
If the merge(other_router) is removed the fallback will work as expected.
// 0.6.12 routes:
// /other -> "other"
// /nested/some-route -> "nested"
// /nested/foo -> "fallback"
// 0.6.13+ routes:
// /other -> "other"
// /nested/some-route -> "nested"
// /nested/foo -> 404
let nested_routes = Router::new()
.route("/some-route", get(|| async { "nested" }))
.fallback(|| async { "fallback" });
let other_router = Router::new()
.route("/other", get(|| async { "other" }));
let app = Router::new()
.nest("/nested", nested_routes)
.merge(other_router); // <-- If removed the fallback() works as expected.Interestingly if you add an outer fallback it will behave as expected:
// 0.6.13+ routes:
// /other -> "other"
// /nested/some-route -> "nested"
// /nested/foo -> "fallback"
// /foo/foo -> "outer fallback"
let nested_routes = Router::new()
.route("/some-route", get(|| async { "nested" }))
.fallback(|| async { "fallback" });
let other_router = Router::new()
.route("/other", get(|| async { "other" }));
let app = Router::new()
.nest("/nested", nested_routes)
.fallback(|| async { "outer fallback" }) // <-- This seems to make the inner fallback work?
.merge(other_router);