.with_state() expects argument with type ()

[jayhale]

• I have looked for existing issues (including closed) about this

Bug Report

Version

$ cargo tree | grep axum
├── axum v0.6.18
│   ├── axum-core v0.3.4

Platform

$ uname -a
Darwin Jamess-Mac-mini.moncrieff.local 22.1.0 Darwin Kernel Version 22.1.0: Sun Oct  9 20:19:47 PDT 2022; root:xnu-8792.41.9~3/RELEASE_ARM64_T8112 arm64

Description

When attempting to replicate the documented usage of .with_state(), checking/building fails because .with_state() expects an argument of type ().

error[E0308]: mismatched types
   --> src/main.rs:28:21
    |
28  |         .with_state(context);
    |          ---------- ^^^^^^^ expected `()`, found `Context`
    |          |
    |          arguments to this method are incorrect
    |
note: method defined here
   --> /Users/james/.cargo/registry/src/index.crates.io-6f17d22bba15001f/axum-0.6.18/src/routing/mod.rs:294:12
    |
294 |     pub fn with_state<S2>(self, state: S) -> Router<S2, B> {
    |            ^^^^^^^^^^

Verbatim main.rs:

use std::env;

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

mod db;
mod config;
mod api;

#[tokio::main]
async fn main() {
    dotenv().ok();
    tracing_subscriber::fmt::init();

    // Get configuration
    let config = config::configure();

    // Set up the database
    let pool = db::connect(&config.database_url).await;

    // Build the app
    let context = api::Context { pool };
    let app = Router::new()
        .route("/", get(|| async { "Flows"}))
        .nest("/v1", api::routes())
        .with_state(context);

    // Serve the app
    tracing::info!("Server starting at http://{:?}", &config.bind_address);
    Server::bind(&config.bind_address)
        .serve(app.into_make_service())
        .await
        .unwrap();
}

[davidpdrsn]

That’s most likely because api::routes returns Router without a state type. See https://docs.rs/axum/latest/axum/routing/struct.Router.html#method.with_state for more details and examples.