Add type safe state extractor (#1155)

* begin threading the state through

* Pass state to extractors

* make state extractor work

* make sure nesting with different states work

* impl Service for MethodRouter<()>

* Fix some of axum-macro's tests

* Implement more traits for `State`

* Update examples to use `State`

* consistent naming of request body param

* swap type params

* Default the state param to ()

* fix docs references

* Docs and handler state refactoring

* docs clean ups

* more consistent naming

* when does MethodRouter implement Service?

* add missing docs

* use `Router`'s default state type param

* changelog

* don't use default type param for FromRequest and RequestParts

probably safer for library authors so you don't accidentally forget

* fix examples

* minor docs tweaks

* clarify how to convert handlers into services

* group methods in one impl block

* make sure merged `MethodRouter`s can access state

* fix docs link

* test merge with same state type

* Document how to access state from middleware

* Port cookie extractors to use state to extract keys (#1250)

* Updates ECOSYSTEM with a new sample project (#1252)

* Avoid unhelpful compiler suggestion (#1251)

* fix docs typo

* document how library authors should access state

* Add `RequestParts::with_state`

* fix example

* apply suggestions from review

* add relevant changes to axum-extra and axum-core changelogs

* Add `route_service_with_tsr`

* fix trybuild expectations

* make sure `SpaRouter` works with routers that have state

* Change order of type params on FromRequest and RequestParts

* reverse order of `RequestParts::with_state` args to match type params

* Add `FromRef` trait (#1268)

* Add `FromRef` trait

* Remove unnecessary type params

* format

* fix docs link

* format examples

* Avoid unnecessary `MethodRouter`

* apply suggestions from review

Co-authored-by: Dani Pardo <[email protected]>
Co-authored-by: Jonas Platte <[email protected]>

examples/sessions/src/main.rs

@@ -7,7 +7,7 @@
 use async_session::{MemoryStore, Session, SessionStore as _};
 use axum::{
     async_trait,
-    extract::{Extension, FromRequest, RequestParts, TypedHeader},
+    extract::{FromRequest, RequestParts, TypedHeader},
     headers::Cookie,
     http::{
         self,
@@ -38,9 +38,7 @@ async fn main() {
     // `MemoryStore` just used as an example. Don't use this in production.
     let store = MemoryStore::new();
 
-    let app = Router::new()
-        .route("/", get(handler))
-        .layer(Extension(store));
+    let app = Router::with_state(store).route("/", get(handler));
 
     let addr = SocketAddr::from(([127, 0, 0, 1], 3000));
     tracing::debug!("listening on {}", addr);
@@ -82,20 +80,16 @@ enum UserIdFromSession {
 }
 
 #[async_trait]
-impl<B> FromRequest<B> for UserIdFromSession
+impl<B> FromRequest<MemoryStore, B> for UserIdFromSession
 where
     B: Send,
 {
     type Rejection = (StatusCode, &'static str);
 
-    async fn from_request(req: &mut RequestParts<B>) -> Result<Self, Self::Rejection> {
-        let Extension(store) = Extension::<MemoryStore>::from_request(req)
-            .await
-            .expect("`MemoryStore` extension missing");
+    async fn from_request(req: &mut RequestParts<MemoryStore, B>) -> Result<Self, Self::Rejection> {
+        let store = req.state().clone();
 
-        let cookie = Option::<TypedHeader<Cookie>>::from_request(req)
-            .await
-            .unwrap();
+        let cookie = req.extract::<Option<TypedHeader<Cookie>>>().await.unwrap();
 
         let session_cookie = cookie
             .as_ref()