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/todos/src/main.rs

@@ -15,7 +15,7 @@
 
 use axum::{
     error_handling::HandleErrorLayer,
-    extract::{Extension, Path, Query},
+    extract::{Path, Query, State},
     http::StatusCode,
     response::IntoResponse,
     routing::{get, patch},
@@ -46,7 +46,7 @@ async fn main() {
     let db = Db::default();
 
     // Compose the routes
-    let app = Router::new()
+    let app = Router::with_state(db)
         .route("/todos", get(todos_index).post(todos_create))
         .route("/todos/:id", patch(todos_update).delete(todos_delete))
         // Add middleware to all routes
@@ -64,7 +64,6 @@ async fn main() {
                 }))
                 .timeout(Duration::from_secs(10))
                 .layer(TraceLayer::new_for_http())
-                .layer(Extension(db))
                 .into_inner(),
         );
 
@@ -85,7 +84,7 @@ pub struct Pagination {
 
 async fn todos_index(
     pagination: Option<Query<Pagination>>,
-    Extension(db): Extension<Db>,
+    State(db): State<Db>,
 ) -> impl IntoResponse {
     let todos = db.read().unwrap();
 
@@ -106,10 +105,7 @@ struct CreateTodo {
     text: String,
 }
 
-async fn todos_create(
-    Json(input): Json<CreateTodo>,
-    Extension(db): Extension<Db>,
-) -> impl IntoResponse {
+async fn todos_create(Json(input): Json<CreateTodo>, State(db): State<Db>) -> impl IntoResponse {
     let todo = Todo {
         id: Uuid::new_v4(),
         text: input.text,
@@ -130,7 +126,7 @@ struct UpdateTodo {
 async fn todos_update(
     Path(id): Path<Uuid>,
     Json(input): Json<UpdateTodo>,
-    Extension(db): Extension<Db>,
+    State(db): State<Db>,
 ) -> Result<impl IntoResponse, StatusCode> {
     let mut todo = db
         .read()
@@ -152,7 +148,7 @@ async fn todos_update(
     Ok(Json(todo))
 }
 
-async fn todos_delete(Path(id): Path<Uuid>, Extension(db): Extension<Db>) -> impl IntoResponse {
+async fn todos_delete(Path(id): Path<Uuid>, State(db): State<Db>) -> impl IntoResponse {
     if db.write().unwrap().remove(&id).is_some() {
         StatusCode::NO_CONTENT
     } else {