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]>

axum-extra/src/extract/form.rs

@@ -55,16 +55,17 @@ impl<T> Deref for Form<T> {
 }
 
 #[async_trait]
-impl<T, B> FromRequest<B> for Form<T>
+impl<T, S, B> FromRequest<S, B> for Form<T>
 where
     T: DeserializeOwned,
     B: HttpBody + Send,
     B::Data: Send,
     B::Error: Into<BoxError>,
+    S: Send,
 {
     type Rejection = FormRejection;
 
-    async fn from_request(req: &mut RequestParts<B>) -> Result<Self, Self::Rejection> {
+    async fn from_request(req: &mut RequestParts<S, B>) -> Result<Self, Self::Rejection> {
         if req.method() == Method::GET {
             let query = req.uri().query().unwrap_or_default();
             let value = serde_html_form::from_str(query)
@@ -85,7 +86,7 @@ where
 }
 
 // this is duplicated in `axum/src/extract/mod.rs`
-fn has_content_type<B>(req: &RequestParts<B>, expected_content_type: &mime::Mime) -> bool {
+fn has_content_type<S, B>(req: &RequestParts<S, B>, expected_content_type: &mime::Mime) -> bool {
     let content_type = if let Some(content_type) = req.headers().get(header::CONTENT_TYPE) {
         content_type
     } else {