[kind of rant] async is overwhelming

Geobomatic · July 27, 2020, 1:07pm

I'm (still) trying to add async support to oxide-auth and with the help of the maintainer, I managed to have a branch that compiles, after 2 weeks of work.

Then I'm trying to use this branch in my project but how to not feel despair when facing this kind of errors (I have 5 or 6 of these):

gist.github.com

https://gist.github.com/Geobert/ac445ed7d2363ec2dcda86f3b2d96bdc

gistfile1.txt

error[E0277]: `dyn oxide_auth_async::code_grant::authorization::Endpoint + std::marker::Send` cannot be shared between threads safely
   --> src\server.rs:115:68
    |
115 |     let get_authorize = warp::path("authorize").and(warp::query()).and_then(
    |                                                                    ^^^^^^^^ `dyn oxide_auth_async::code_grant::authorization::Endpoint + std::marker::Send` cannot be shared between threads safely
    |
    = help: the trait `std::marker::Sync` is not implemented for `dyn oxide_auth_async::code_grant::authorization::Endpoint + std::marker::Send`
    = note: required because of the requirements on the impl of `std::marker::Send` for `&dyn oxide_auth_async::code_grant::authorization::Endpoint + std::marker::Send`
    = note: required because it appears within the type `for<'r, 's, 't0, 't1, 't2, 't3, 't4, 't5, 't6, 't7, 't8, 't9, 't10, 't11, 't12, 't13> {std::future::ResumeTy, &'r mut (dyn oxide_auth_async::code_grant::authorization::Endpoint + std::marker::Send + 's), &'t0 (dyn oxide_auth::code_grant::authorization::Request + std::marker::Sync + 't1), oxide_auth::code_grant::authorization::Authorization, oxide_auth_async::code_grant::authorization::authorization_code::{{closure}}#0::Requested, std::option::Option<url::Url>, std::string::String, oxide_auth::primitives::registrar::ClientUrl<'t2>, &'t3 (dyn oxide_auth_async::code_grant::authorization::Endpoint + std::marker::Send 
+ 't4), &'t5 (dyn oxide_auth_async::primitives::Registrar + 't6), std::pin::Pin<std::boxed::Box<(dyn core::future::future::Future<Output = std::result::Result<oxide_auth::primitives::registrar::BoundClient<'t7>, oxide_auth::primitives::registrar::RegistrarError>> + std::marker::Send + 't8)>>, (), &'t9 mut (dyn oxide_auth_async::code_grant::authorization::Extension + 't10), std::pin::Pin<std::boxed::Box<(dyn core::future::future::Future<Output = std::result::Result<oxide_auth::primitives::grant::Extensions, ()>> + std::marker::Send + 't11)>>, url::Url, std::option::Option<oxide_auth::primitives::scope::Scope>, oxide_auth::primitives::registrar::BoundClient<'t12>, std::pin::Pin<std::boxed::Box<(dyn core::future::future::Future<Output = std::result::Result<oxide_auth::primitives::registrar::PreGrant, oxide_auth::primitives::registrar::RegistrarError>> + std::marker::Send + 't13)>>}`

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This was one of the thing I hate on C++ (mega extra long wall of error messages) and it seems we're being hit by it as well Maybe for a good reason, but it is discouraging that after so much work on the library side, trying to use it throw a wall at your face.

Not really usefull post here, just need a shoulder to cry on ^^'

alice · July 27, 2020, 1:12pm

This is definitely one of the error messages that could use work.

Geobomatic · July 27, 2020, 2:03pm

Especially a better location. In my example, it's on the "root" of the async call tree, so I have to read the whole code looking for where the type is used.

alice · July 27, 2020, 2:14pm

It is also non-obvious if you're doing it wrong with this specific error, because the error is that an immutable reference to some type is stored across an .await. The type itself is ok to store, but not the immutable reference.

Geobomatic · July 27, 2020, 2:49pm

you lost me ^^'