[MIT License 2021 Edgar ONGHENA] Extension trait to use Diesel ORM asynchronously with rocket 0.5 and rocket_contrib 0.5

async_diesel.rs

/* Copyright Edgar ONGHENA 2021. All Rights Reserved.
   This file is licensed under the MIT License.
   License text available at https://opensource.org/licenses/MIT
   This header may be removed if the terms of the license are still respected
   (including, but not limited to, giving proper credit somewhere else) */

use diesel::dsl::Limit;
use diesel::query_dsl::limit_dsl::LimitDsl;
use diesel::query_dsl::LoadQuery;
use diesel::{QueryResult, RunQueryDsl};

type ConnWrapper = crate::FIXME;
type Conn = rocket_contrib::databases::diesel::PgConnection;

#[rocket::async_trait]
pub trait AsyncRunQueryDsl {
    async fn load_async<U>(self, conn: &ConnWrapper) -> QueryResult<Vec<U>>
    where
        Self: LoadQuery<Conn, U>,
        QueryResult<Vec<U>>: 'static + Send;

    async fn get_result_async<U>(self, conn: &ConnWrapper) -> QueryResult<U>
    where
        Self: LoadQuery<Conn, U>,
        QueryResult<U>: 'static + Send;

    async fn get_results_async<U>(self, conn: &ConnWrapper) -> QueryResult<Vec<U>>
    where
        Self: LoadQuery<Conn, U>,
        QueryResult<Vec<U>>: 'static + Send;

    async fn first_async<U>(self, conn: &ConnWrapper) -> QueryResult<U>
    where
        Self: LimitDsl,
        Limit<Self>: LoadQuery<Conn, U>,
        QueryResult<U>: 'static + Send;
}

#[rocket::async_trait]
impl<T: 'static + Send + RunQueryDsl<Conn>> AsyncRunQueryDsl for T {
    async fn load_async<U>(self, conn: &ConnWrapper) -> QueryResult<Vec<U>>
    where
        Self: LoadQuery<Conn, U>,
        QueryResult<Vec<U>>: 'static + Send,
    {
        conn.run(move |db| self.load(db)).await
    }

    async fn get_result_async<U>(self, conn: &ConnWrapper) -> QueryResult<U>
    where
        Self: LoadQuery<Conn, U>,
        QueryResult<U>: 'static + Send,
    {
        conn.run(move |db| self.get_result(db)).await
    }

    async fn get_results_async<U>(self, conn: &ConnWrapper) -> QueryResult<Vec<U>>
    where
        Self: LoadQuery<Conn, U>,
        QueryResult<Vec<U>>: 'static + Send,
    {
        conn.run(move |db| self.get_results(db)).await
    }

    async fn first_async<U>(self, conn: &ConnWrapper) -> QueryResult<U>
    where
        Self: LimitDsl,
        Limit<Self>: LoadQuery<Conn, U>,
        QueryResult<U>: 'static + Send,
    {
        conn.run(move |db| self.first(db)).await
    }
}

Usage: import the trait and add _async behind any of the load, get_result, get_results or first methods in any diesel request. Don't forget to .await the returned value.