anyhow-error-response

[package]
name = "example-anyhow-error-response"
version = "0.1.0"
edition = "2021"
publish = false

[dependencies]
anyhow = "1.0"
axum = { path = "../../axum" }
tokio = { version = "1.0", features = ["full"] }

[dev-dependencies]
http-body-util = "0.1.0"
tower = { version = "0.5.2", features = ["util"] }

//! Run with
//!
//! ```not_rust
//! cargo run -p example-anyhow-error-response
//! ```

use axum::{
    http::StatusCode,
    response::{IntoResponse, Response},
    routing::get,
    Router,
};

#[tokio::main]
async fn main() {
    let app = app();

    let listener = tokio::net::TcpListener::bind("127.0.0.1:3000")
        .await
        .unwrap();
    println!("listening on {}", listener.local_addr().unwrap());
    axum::serve(listener, app).await.unwrap();
}

async fn handler() -> Result<(), AppError> {
    try_thing()?;
    Ok(())
}

fn try_thing() -> Result<(), anyhow::Error> {
    anyhow::bail!("it failed!")
}

// Make our own error that wraps `anyhow::Error`.
struct AppError(anyhow::Error);

// Tell axum how to convert `AppError` into a response.
impl IntoResponse for AppError {
    fn into_response(self) -> Response {
        (
            StatusCode::INTERNAL_SERVER_ERROR,
            format!("Something went wrong: {}", self.0),
        )
            .into_response()
    }
}

fn app() -> Router {
    Router::new().route("/", get(handler))
}

// This enables using `?` on functions that return `Result<_, anyhow::Error>` to turn them into
// `Result<_, AppError>`. That way you don't need to do that manually.
impl<E> From<E> for AppError
where
    E: Into<anyhow::Error>,
{
    fn from(err: E) -> Self {
        Self(err.into())
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use axum::{body::Body, http::Request, http::StatusCode};
    use http_body_util::BodyExt;
    use tower::ServiceExt;

    #[tokio::test]
    async fn test_main_page() {
        let response = app()
            .oneshot(Request::builder().uri("/").body(Body::empty()).unwrap())
            .await
            .unwrap();

        assert_eq!(response.status(), StatusCode::INTERNAL_SERVER_ERROR);
        let body = response.into_body();
        let bytes = body.collect().await.unwrap().to_bytes();
        let html = String::from_utf8(bytes.to_vec()).unwrap();

        assert_eq!(html, "Something went wrong: it failed!");
    }
}

$ curl -i  http://localhost:3000
HTTP/1.1 500 Internal Server Error
content-type: text/plain; charset=utf-8
content-length: 32
date: Sun, 16 Mar 2025 16:18:04 GMT

Something went wrong: it failed!