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Implement Handler for T: IntoResponse #2140

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merged 3 commits into from
Aug 2, 2023
Merged

Implement Handler for T: IntoResponse #2140

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d2fd9b2
Implement `Handler` for `T: IntoResponse`
davidpdrsn Aug 2, 2023
a8c8fb8
add some docs
davidpdrsn Aug 2, 2023
fb9022c
changelog number
davidpdrsn Aug 2, 2023
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2 changes: 2 additions & 0 deletions axum/CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -62,6 +62,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
- **fixed:** Allow unreachable code in `#[debug_handler]` ([#2014])
- **change:** Update tokio-tungstenite to 0.19 ([#2021])
- **change:** axum's MSRV is now 1.63 ([#2021])
- **added:** Implement `Handler` for `T: IntoResponse` ([#2140])

[#2021]: https://github.com/tokio-rs/axum/pull/2021
[#2014]: https://github.com/tokio-rs/axum/pull/2014
Expand All @@ -78,6 +79,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
[#2058]: https://github.com/tokio-rs/axum/pull/2058
[#2073]: https://github.com/tokio-rs/axum/pull/2073
[#2096]: https://github.com/tokio-rs/axum/pull/2096
[#2140]: https://github.com/tokio-rs/axum/pull/2140

# 0.6.17 (25. April, 2023)

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42 changes: 42 additions & 0 deletions axum/src/handler/mod.rs
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Expand Up @@ -100,6 +100,31 @@ pub use self::service::HandlerService;
/// {}
/// ```
#[doc = include_str!("../docs/debugging_handler_type_errors.md")]
///
/// # Handlers that aren't functions
///
/// The `Handler` trait is also implemented for `T: IntoResponse`. That allows easily returning
/// fixed data for routes:
///
/// ```
/// use axum::{
/// Router,
/// routing::{get, post},
/// Json,
/// http::StatusCode,
/// };
/// use serde_json::json;
///
/// let app = Router::new()
/// // respond with a fixed string
/// .route("/", get("Hello, World!"))
/// // or return some mock data
/// .route("/users", post((
/// StatusCode::CREATED,
/// Json(json!({ "id": 1, "username": "alice" })),
/// )));
/// # let _: Router = app;
/// ```
#[cfg_attr(
nightly_error_messages,
rustc_on_unimplemented(
Expand Down Expand Up @@ -224,6 +249,23 @@ macro_rules! impl_handler {

all_the_tuples!(impl_handler);

mod private {
// Marker type for `impl<T: IntoResponse> Handler for T`
#[allow(missing_debug_implementations)]
pub enum IntoResponseHandler {}
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I don't think this needs to have pub visibility? At least on my v0.6.x based branch, things compiled with a private marker type.

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It didn't actually work when I tried using it

error: type `handler::IntoResponseHandler` is private
  --> examples/hello-world/src/main.rs:12:40
   |
12 |     let app = Router::new().route("/", get(StatusCode::OK));
   |                                        ^^^ private type

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What, at the usage site?? 😱

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yeah that confused me as well. Haven't seen that before.

}

impl<T, S> Handler<private::IntoResponseHandler, S> for T
where
T: IntoResponse + Clone + Send + 'static,
{
type Future = std::future::Ready<Response>;

fn call(self, _req: Request, _state: S) -> Self::Future {
std::future::ready(self.into_response())
}
}

/// A [`Service`] created from a [`Handler`] by applying a Tower middleware.
///
/// Created with [`Handler::layer`]. See that method for more details.
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11 changes: 11 additions & 0 deletions axum/src/routing/tests/mod.rs
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Expand Up @@ -1021,3 +1021,14 @@ async fn connect_going_to_default_fallback() {
let body = hyper::body::to_bytes(res).await.unwrap();
assert!(body.is_empty());
}

#[crate::test]
async fn impl_handler_for_into_response() {
let app = Router::new().route("/things", post((StatusCode::CREATED, "thing created")));

let client = TestClient::new(app);

let res = client.post("/things").send().await;
assert_eq!(res.status(), StatusCode::CREATED);
assert_eq!(res.text().await, "thing created");
}