Diesel's attribute `primary_key` is currently unknown to the compiler

Question

I'm trying to use the #[primarykey()] macro in Diesel but am getting an error that it is unknown. From what I have found, adding #![feature(primary_key)] should solve the issue, but it doesn't.

lib.rs

#[macro_use]
extern crate diesel;
extern crate dotenv;

pub mod schema;
pub mod models;

use diesel::prelude::*;
use diesel::pg::PgConnection;
use dotenv::dotenv;
use std::env;

pub fn establish_connection() -> PgConnection {
    dotenv().ok();

    let database_url = env::var("DATABASE_URL")
        .expect("DATABASE_URL must be set");
    PgConnection::establish(&database_url)
        .expect(&format!("Error connecting to {}", database_url))
}

models.rs

#![feature(primary_key)]

extern crate diesel;

#[derive(Queryable, Debug)]
#[primary_key(user_id)]
pub struct User {
    pub user_id: i32,
    pub email: String,
    pub password: String,
    pub bio: String,
    pub verified: bool,
}

I've also tried adding #![feature(primary_key)] to the top of lib.rs without any luck.

Using Rust 1.26.0-nightly (80785a547 2018-03-30)

Answer 1

The primary_key attribute is only applicable when deriving Identifiable:

#[macro_use]
extern crate diesel;

mod schema {
    table! {
        users (user_id) {
            user_id -> Int4,
            email -> Text,
        }
    }

    #[derive(Debug, Identifiable)]
    #[primary_key(email)]
    pub struct User {
        pub user_id: i32,
        pub email: String,
    }
}

fn main() {}

I believe you could also just change your primary key in your schema definition (users (user_id)).