OpenSource/axum
OpenSource/axum
1
0
Fork 0
mirror of https://github.com/tokio-rs/axum.git synced 2024-11-21 22:56:46 +01:00
Code Issues Projects Releases Packages Wiki Activity

Document debugging handler type errors with "axum-debug" (#372)

Browse source 
* Document debugging handler type errors with "axum-debug"

* Apply suggestions from code review

Co-authored-by: Jonas Platte <jplatte@users.noreply.github.com>

Co-authored-by: Jonas Platte <jplatte@users.noreply.github.com>
This commit is contained in:
David Pedersen 2021-10-07 15:33:49 +02:00 committed by GitHub
parent d29c1f26c2
commit 5dc5a7cb6e
No known key found for this signature in database
GPG key ID: 4AEE18F83AFDEB23
1 changed files with 39 additions and 0 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

39
src/lib.rs
View file

@ -5,6 +5,7 @@
//! - [High level features](#high-level-features)
//! - [Compatibility](#compatibility)
//! - [Handlers](#handlers)
//! - [Debugging handler type errors](#debugging-handler-type-errors)
//! - [Routing](#routing)
//! - [Precedence](#precedence)
//! - [Matching multiple methods](#matching-multiple-methods)
@ -106,6 +107,41 @@
//! }
//! ```
//!
//! ## Debugging handler type errors
//!
//! For a function to used as a handler it must implement the [`Handler`] trait.
//! axum provides blanket implementations for functions that:
//!
//! - Are `async fn`s.
//! - Take no more than 16 arguments that all implement [`FromRequest`].
//! - Returns something that implements [`IntoResponse`].
//! - If a closure is used it must implement `Clone + Send + Sync` and be
//! `'static`.
//! - Returns a future that is `Send`. The most common way to accidentally make a
//! future `!Send` is to hold a `!Send` type across an await.
//!
//! Unfortunately Rust gives poor error messages if you try to use a function
//! that doesn't quite match what's required by [`Handler`].
//!
//! You might get an error like this:
//!
//! ```not_rust
//! error[E0277]: the trait bound `fn(bool) -> impl Future {handler}: Handler<_, _>` is not satisfied
//! --> src/main.rs:13:44
//! |
//! 13 | let app = Router::new().route("/", get(handler));
//! | ^^^^^^^ the trait `Handler<_, _>` is not implemented for `fn(bool) -> impl Future {handler}`
//! |
//! ::: axum/src/handler/mod.rs:116:8
//! |
//! 116 | H: Handler<B, T>,
//! | ------------- required by this bound in `axum::handler::get`
//! ```
//!
//! This error doesn't tell you _why_ your function doesn't implement
//! [`Handler`]. It's possible to improve the error with the [`debug_handler`]
//! proc-macro from the [axum-debug] crate.
//!
//! # Routing
//!
//! Routing between handlers looks like this:
@ -1150,6 +1186,9 @@
//! [`HeaderMap`]: http::header::HeaderMap
//! [`Request`]: http::Request
//! [customize-extractor-error]: https://github.com/tokio-rs/axum/blob/main/examples/customize-extractor-error/src/main.rs
//! [axum-debug]: https://docs.rs/axum-debug
//! [`debug_handler`]: https://docs.rs/axum-debug/latest/axum_debug/attr.debug_handler.html
//! [`Handler`]: crate::handler::Handler
#![warn(
clippy::all,