? on surf::Exception

[abreis]

I'm working on a simple app using async/await and Surf, and I can't seem to use it with anyhow.

Here's a minimal example:

async fn some_request() -> anyhow::Result<()> {
    let _response = surf::get("https://www.rust-lang.org").await?;
    Ok(())
}

cargo +beta check complains with:

error[E0277]: the size for values of type `dyn std::error::Error + std::marker::Send + std::marker::Sync` cannot be known at compilation time
 --> src/main.rs:8:64
  |
8 |     let response = surf::get("https://www.rust-lang.org").await?;
  |                                                                ^ doesn't have a size known at compile-time
  |
  = help: the trait `std::marker::Sized` is not implemented for `dyn std::error::Error + std::marker::Send + std::marker::Sync`
  = note: to learn more, visit <https://doc.rust-lang.org/book/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
  = note: required because of the requirements on the impl of `std::error::Error` for `std::boxed::Box<dyn std::error::Error + std::marker::Send + std::marker::Sync>`
  = note: required because of the requirements on the impl of `std::convert::From<std::boxed::Box<dyn std::error::Error + std::marker::Send + std::marker::Sync>>` for `anyhow::Error`
  = note: required by `std::convert::From::from`

I can't tell if this is an issue with anyhow, with surf, with the .await, or if I'm doing something wrong.

[dtolnay]

This is because Surf is using a silly choice of error type. :( http-rs/surf#86
Libraries should return errors that implement std::error::Error in order for ? to work, and Surf's does not.

For now you can work around this by avoiding ?:

use anyhow::{bail, Result};

async fn some_request() -> Result<()> {
    let _response = match surf::get("https://www.rust-lang.org").await {
        Ok(response) => response,
        Err(err) => bail!(err),
    };

    ...
}

[abreis]

Thanks!

[mchlrhw]

I know this is closed, but I found myself here recently so I thought I'd share another approach.
If you want to add a context to surf errors, or want to make use of ?, you can do:

use anyhow::{anyhow, Context, Result};

async fn some_request() -> Result<()> {
    let _response = surf::get("https://www.rust-lang.org")
        .await
        .map_err(|err| anyhow!(err)) // TODO: Remove me when surf 2.0 is released
        .context("Failed to fetch from rust-lang.org")?;

    ...
}