ResExt v0.7.0 - complete redesign

[Tahaa-Dev]

As of now, ResExt uses a trait-based API where you import the ResExt trait and ErrCtx<E> struct and use the methods provided by ResExt for error-handling similar to anyhow.

But as it's clear from recent commits and updates to the repository, ResExt is trying to to start using a hybrid approach between thiserror and anyhow by providing the enumerate! {} macro to generate error enums with ResExt implementations.

The problem

This approach has hit a few issues in integration tests, specifically with the orphan rule (error E0117):

// This fails in integration tests:
impl From<std::io::Error> for ErrCtx<MyError> {
    //   ^^^^^^^^^^^^         ^^^^^^^^^^^^^^^^
    //   Foreign type         Foreign type (from resext crate)
    // Error E0117: orphan rule violation
}

The solution

So in next versions, ResExt will be using a completely new approach for its types and traits, ResExt will use a new macro called ResExt! { enum } instead of separate traits and types that generates:

• ResErr type (similar to ErrCtx<E>)
• A full error enum with full From, Error, Display and Debug implementations
• ResExt trait with all of its methods and two implementations for Result<T, E> and Result<T, ResErr>
• Res<T> type alias with optional aliases instead of Res

All locally in your project!

Example

Error handling with ResExt v0.7.0+ would look like:

use resext::ResExt;
use serde_json::Value;

ResExt! {
    enum MyError {
        Io(std::io::Error),
        Network(reqwest::Error),
        Parse(serde_json::Error),
        Other,
    }
}

async fn fetch_data(url: String) -> Res<Data> {
    let data = reqwest::get(url).await.with_context(|| format!("Failed to fetch URL: {}", url))?;

    let config_content = std::fs::read("config.json").context("Failed to read config")?;
    
    let config = serde_json::from_slice(&config_content).context("Failed to parse config")?;

    let parsed_data: Data = crate::parse_data(config, data);

    Ok(parsed_data)
}

Why This Change?

While ResExt's priority is low-cost error handling, ergonomics still matter. This redesign achieves both:

• Solves orphan rule issues: everything is generated locally
• Simpler API: just a declarative macro
• Better maintainability: one focused feature, easier to maintain in the future
• Works everywhere: lib crates, binary crates, integration tests, examples

Notes

1. This is not a drop-in replacement for ResExt v0.6.x, this next version will break any old code with ResExt.
2. A migration guide will be added soon for ResExt v0.7.0
3. If you need any help migrating, feel free to comment on this discussion or open an issue, we're here to help!