Use Arc for SeaRc with feature flag

[tqwewe]

Given the following function in a tokio runtime:

async fn update(
    db: &DatabaseConnection,
    active_model: model::ActiveModel,
) -> Result<bool, Box<dyn std::error::Error>> {
    Entity::update(active_model)
        .exec(db)
        .await
        .map_err(Box::new)?;

    Ok(true)
}

An error is thrown due to SeaRc not implementing Send.

error: future cannot be sent between threads safely
   |
76 |       ) -> Result<bool, Box<dyn std::error::Error>> {
   |  ___________________________________________________^
77 | |         use models::coupons::Entity as Coupon;
78 | |
79 | |         let res = Coupon::update(coupon_update)
...  |
84 | |         Ok(true)
85 | |     }
   | |_____^ future created by async block is not `Send`
   |
   = help: within `TableRef`, the trait `std::marker::Send` is not implemented for `SeaRc<(dyn Iden + 'static)>`

pub use std::rc::Rc as SeaRc; should be updated to use Arc instead of Rc, either perminently or through a feature flag.

[tyt2y3]

I think you encountered a problem in SeaORM.
Yes I was aware of the async quirk. I still believe we can keep the query building stage on the same thread, then we would not requite Arc.
But I do agree we can add a feature flag for this as a workaround, and enable it by default in SeaORM.

[tqwewe]

Yes this is an error I encountered in SeaORM. I don't know of any workaround, it seems like the only option is that SeaRc to be changed to Arc. I agree that enabling this in SeaORM by default would be best 👍

[tyt2y3]

0.14.0

[tqwewe]

Thanks for the commits for this.

Unfortunately, I get an error still with SeaORM with my same code:

the trait `std::marker::Send` is not implemented for `(dyn Iden + 'static)`

I have enabled the "thread-safe" flag and can confirm it's using Arc. There may need to be some other code updates to resolve this.

[tyt2y3]

Please open an issue in SeaORM