Reqwest: Crates that use the unstable feature can't compile with 2018 edition preview since async is a keyword

[Arnavion]

If some code references reqwest::unstable::async it'll fail to compile:

let mut builder = ::reqwest::unstable::async::ClientBuilder::new();

19 | let mut builder = ::reqwest::unstable::async::ClientBuilder::new();
   |                                        ^^^^^ expected identifier, found reserved keyword

I don't know if this is a bit of backward-compatibility that will be fixed, or if reqwest will have to rename the module to something else.

(Trying to rename the import like use reqwest::unstable::async as reqwest_async; doesn't help either since now the error is on this use statement instead.)

Edit: #rust reminded me that raw idents exist for this purpose, so ::reqwest::unstable::r#async works fine. But maybe reqwest should rename it anyway so that everyone doesn't have to use raw idents?

[seanmonstar]

Sigh, that's unfortunate. The name feels like the right fit, as there is both sync and async clients...

[Arnavion]

Maybe prefix the types with Async instead?

The users who used direct references would still have to write the same number of asyncs
Before: let mut builder = ::reqwest::unstable::async::ClientBuilder::new();
After: let mut builder = ::reqwest::unstable::AsyncClientBuilder::new();

The users who didn't want to repeately type async in the first place and so used a use statement would also have to write the same number of asyncs
Before: use reqwest::unstable::async::ClientBuilder; let mut builder = ClientBuilder::new();
After: use reqwest::unstable::AsyncClientBuilder as ClientBuilder; let mut builder = ClientBuilder::new();

But the users who used wildcard imports use reqwest::unstable::async::* would have to write more Asyncs now.

[mehcode]

My (perhaps unpopular) opinion is that the sync client should be thrown out for a strictly async API.

In sync contexts an upgrade path would be:

// 0.8.x
let mut res = reqwest::get("https://www.rust-lang.org/en-US/")?;

// 0.9.x
let mut res = reqwest::get("https://www.rust-lang.org/en-US/").wait()?;

I don't see this as nearly the insurmountable ergonomic issue that it was. Especially with the std focus of async / await / futures. Maybe it's not appropriate to do this until 0.10.x when perhaps async fn is stable syntax.

---

Another idea would be to keep the sync API but make async the default and stash sync at reqwest::sync::*.

[galich]

@seanmonstar may be make async_impl module public meanwhile? It's not a perfect solution, but it will allow us to use reqwest with Rust 2018 until better solution arrives.

[seanmonstar]

Anyone using Rust 2018 can still use reqwest by using "raw identifiers": use reqwest::unstable::r#async::Client;

[galich]

thanks, that suites our needs here perfectly!