Release axum - v0.6.0 · tokio-rs/axum

Routing

fixed: Nested routers are now allowed to have fallbacks (#1521):

let api_router = Router::new()
    .route("/users", get(|| { ... }))
    .fallback(api_fallback);

let app = Router::new()
    // this would panic in 0.5 but in 0.6 it just works
    //
    // requests starting with `/api` but not handled by `api_router`
    // will go to `/api_fallback`
    .nest("/api", api_router);

The outer router's fallback will still apply if a nested router doesn't have
its own fallback:

// this time without a fallback
let api_router = Router::new().route("/users", get(|| { ... }));

let app = Router::new()
    .nest("/api", api_router)
    // `api_fallback` will inherit this fallback
    .fallback(app_fallback);

breaking: The request /foo/ no longer matches /foo/*rest. If you want
to match /foo/ you have to add a route specifically for that (#1086)

For example:

use axum::{Router, routing::get, extract::Path};

let app = Router::new()
    // this will match `/foo/bar/baz`
    .route("/foo/*rest", get(handler))
    // this will match `/foo/`
    .route("/foo/", get(handler))
    // if you want `/foo` to match you must also add an explicit route for it
    .route("/foo", get(handler));

async fn handler(
    // use an `Option` because `/foo/` and `/foo` don't have any path params
    params: Option<Path<String>>,
) {}

breaking: Path params for wildcard routes no longer include the prefix
/. e.g. /foo.js will match /*filepath with a value of foo.js, not
/foo.js (#1086)

For example:

use axum::{Router, routing::get, extract::Path};

let app = Router::new().route("/foo/*rest", get(handler));

async fn handler(
    Path(params): Path<String>,
) {
    // for the request `/foo/bar/baz` the value of `params` will be `bar/baz`
    //
    // on 0.5 it would be `/bar/baz`
}

fixed: Routes like /foo and /*rest are no longer considered
overlapping. /foo will take priority (#1086)

For example:

use axum::{Router, routing::get};

let app = Router::new()
    // this used to not be allowed but now just works
    .route("/foo/*rest", get(foo))
    .route("/foo/bar", get(bar));

async fn foo() {}

async fn bar() {}

breaking: Automatic trailing slash redirects have been removed.
Previously if you added a route for /foo, axum would redirect calls to
/foo/ to /foo (or vice versa for /foo/):

use axum::{Router, routing::get};

let app = Router::new()
    // a request to `GET /foo/` will now get `404 Not Found`
    // whereas in 0.5 axum would redirect to `/foo`
    //
    // same goes the other way if you had the route `/foo/`
    // axum will no longer redirect from `/foo` to `/foo/`
    .route("/foo", get(handler));

async fn handler() {}

Either explicitly add routes for /foo and /foo/ or use
axum_extra::routing::RouterExt::route_with_tsr if you want the old behavior
(#1119)

breaking: Router::fallback now only accepts Handlers (similarly to
what get, post, etc. accept). Use the new Router::fallback_service for
setting any Service as the fallback (#1155)

This fallback on 0.5:

use axum::{Router, handler::Handler};

let app = Router::new().fallback(fallback.into_service());

async fn fallback() {}

Becomes this in 0.6

use axum::Router;

let app = Router::new().fallback(fallback);

async fn fallback() {}

changed: Router::nest now only accepts Routers, the general-purpose
Service nesting method has been renamed to nest_service (#1368)
breaking: Allow Error: Into<Infallible> for Route::{layer, route_layer} (#924)
breaking: MethodRouter now panics on overlapping routes (#1102)
breaking: Router::route now only accepts MethodRouters created with
get, post, etc. Use the new Router::route_service for routing to
any Services (#1155)
breaking: Adding a .route_layer onto a Router or MethodRouter
without any routes will now result in a panic. Previously, this just did
nothing. #1327
breaking: RouterService has been removed since Router now implements
Service when the state is (). Use Router::with_state to provide the
state and get a Router<()>. Note that RouterService only existed in the
pre-releases, not 0.5 (#1552)

Extractors

added: Added new type safe State extractor. This can be used with
Router::with_state and gives compile errors for missing states, whereas
Extension would result in runtime errors (#1155)

We recommend migrating from Extension to State for sharing application state since that is more type
safe and faster. That is done by using Router::with_state and State.

This setup in 0.5

use axum::{routing::get, Extension, Router};

let app = Router::new()
    .route("/", get(handler))
    .layer(Extension(AppState {}));

async fn handler(Extension(app_state): Extension<AppState>) {}

#[derive(Clone)]
struct AppState {}

Becomes this in 0.6 using State:

use axum::{routing::get, extract::State, Router};

let app = Router::new()
    .route("/", get(handler))
    .with_state(AppState {});

async fn handler(State(app_state): State<AppState>) {}

#[derive(Clone)]
struct AppState {}

If you have multiple extensions, you can use fields on AppState and implement
FromRef:

use axum::{extract::{State, FromRef}, routing::get, Router};

let state = AppState {
    client: HttpClient {},
    database: Database {},
};

let app = Router::new().route("/", get(handler)).with_state(state);

async fn handler(
    State(client): State<HttpClient>,
    State(database): State<Database>,
) {}

// the derive requires enabling the "macros" feature
#[derive(Clone, FromRef)]
struct AppState {
    client: HttpClient,
    database: Database,
}

#[derive(Clone)]
struct HttpClient {}

#[derive(Clone)]
struct Database {}

breaking: It is now only possible for one extractor per handler to consume
the request body. In 0.5 doing so would result in runtime errors but in 0.6 it
is a compile error (#1272)

axum enforces this by only allowing the last extractor to consume the
request.

For example:

use axum::{Json, http::HeaderMap};

// This wont compile on 0.6 because both `Json` and `String` need to consume
// the request body. You can use either `Json` or `String`, but not both.
async fn handler_1(
    json: Json<serde_json::Value>,
    string: String,
) {}

// This won't work either since `Json` is not the last extractor.
async fn handler_2(
    json: Json<serde_json::Value>,
    headers: HeaderMap,
) {}

// This works!
async fn handler_3(
    headers: HeaderMap,
    json: Json<serde_json::Value>,
) {}

This is done by reworking the FromRequest trait and introducing a new
FromRequestParts trait.

If your extractor needs to consume the request body then you should implement
FromRequest, otherwise implement FromRequestParts.

This extractor in 0.5:

struct MyExtractor { /* ... */ }

#[async_trait]
impl<B> FromRequest<B> for MyExtractor
where
    B: Send,
{
    type Rejection = StatusCode;

    async fn from_request(req: &mut RequestParts<B>) -> Result<Self, Self::Rejection> {
        // ...
    }
}

Becomes this in 0.6:

use axum::{
    extract::{FromRequest, FromRequestParts},
    http::{StatusCode, Request, request::Parts},
    async_trait,
};

struct MyExtractor { /* ... */ }

// implement `FromRequestParts` if you don't need to consume the request body
#[async_trait]
impl<S> FromRequestParts<S> for MyExtractor
where
    S: Send + Sync,
{
    type Rejection = StatusCode;

    async fn from_request_parts(parts: &mut Parts, state: &S) -> Result<Self, Self::Rejection> {
        // ...
    }
}

// implement `FromRequest` if you do need to consume the request body
#[async_trait]
impl<S, B> FromRequest<S, B> for MyExtractor
where
    S: Send + Sync,
    B: Send + 'static,
{
    type Rejection = StatusCode;

    async fn from_request(req: Request<B>, state: &S) -> Result<Self, Self::Rejection> {
        // ...
    }
}

For an example of how to write an extractor that accepts different
Content-Types see the parse-body-based-on-content-type example.

added: FromRequest and FromRequestParts derive macro re-exports from
axum-macros behind the macros feature (#1352)
added: Add RequestExt and RequestPartsExt which adds convenience
methods for running extractors to http::Request and http::request::Parts (#1301)
added: JsonRejection now displays the path at which a deserialization
error occurred (#1371)
added: Add extract::RawForm for accessing raw urlencoded query bytes or request body (#1487)
fixed: Used 400 Bad Request for FailedToDeserializeQueryString
rejections, instead of 422 Unprocessable Entity (#1387)
changed: The inner error of a JsonRejection is now
serde_path_to_error::Error<serde_json::Error>. Previously it was
serde_json::Error (#1371)
changed: The default body limit now applies to the Multipart extractor (#1420)
breaking: ContentLengthLimit has been removed. Use DefaultBodyLimit instead (#1400)
breaking: RequestParts has been removed as part of the FromRequest
rework (#1272)
breaking: BodyAlreadyExtracted has been removed (#1272)
breaking: The following types or traits have a new S type param
which represents the state (#1155):
- Router, defaults to ()
- MethodRouter, defaults to ()
- FromRequest, no default
- Handler, no default
breaking: MatchedPath can now no longer be extracted in middleware for
nested routes. In previous versions it returned invalid data when extracted
from a middleware applied to a nested router. MatchedPath can still be
extracted from handlers and middleware that aren't on nested routers (#1462)
breaking: Rename FormRejection::FailedToDeserializeQueryString to
FormRejection::FailedToDeserializeForm (#1496)

Middleware

added: Support running extractors on middleware::from_fn functions (#1088)
added: Add middleware::from_fn_with_state to enable running extractors that require
state (#1342)
added: Add middleware::from_extractor_with_state (#1396)
added: Add map_request, map_request_with_state for transforming the
request with an async function (#1408)
added: Add map_response, map_response_with_state for transforming the
response with an async function (#1414)
added: Support any middleware response that implements IntoResponse (#1152)
breaking: Remove extractor_middleware which was previously deprecated.
Use axum::middleware::from_extractor instead (#1077)
breaking: Require middleware added with Handler::layer to have
Infallible as the error type (#1152)

Misc

added: Support compiling to WASM. See the simple-router-wasm example
for more details (#1382)
added: Add ServiceExt with methods for turning any Service into a
MakeService similarly to Router::into_make_service (#1302)
added: String and binary From impls have been added to extract::ws::Message
to be more inline with tungstenite (#1421)
added: Add #[derive(axum::extract::FromRef)] (#1430)
added: Add accept_unmasked_frames setting in WebSocketUpgrade (#1529)
added: Add WebSocketUpgrade::on_failed_upgrade to customize what to do
when upgrading a connection fails (#1539)
fixed: Annotate panicking functions with #[track_caller] so the error
message points to where the user added the invalid route, rather than
somewhere internally in axum (#1248)
changed: axum's MSRV is now 1.60 (#1239)
changed: For methods that accept some S: Service, the bounds have been
relaxed so the response type must implement IntoResponse rather than being a
literal Response
breaking: New tokio default feature needed for WASM support. If you
don't need WASM support but have default_features = false for other reasons
you likely need to re-enable the tokio feature (#1382)
breaking: handler::{WithState, IntoService} are merged into one type,
named HandlerService (#1418)

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axum - v0.6.0

Routing

Extractors

Middleware

Misc