chewie-macros

Procedural macros for the chewie-auth ecosystem.

This crate provides compile-time code generation to reduce boilerplate and improve developer experience.

Macros

define_boxed_error!

Generates a type-erased error type with downcast support.

use chewie_macros::define_boxed_error;

define_boxed_error! {
    /// HTTP client error.
    pub HttpError {
        display: "HTTP error",
    }
}

This generates:

• Error struct with Box<dyn Error> field (with Send + Sync bounds when send feature is enabled)
• Display and Error trait implementations
• downcast_ref<E>() and downcast<E>() methods for error inspection
• inner() method to access the underlying error

Example: Basic Usage

use chewie_macros::define_boxed_error;

define_boxed_error! {
    /// Error returned by the token validation layer.
    pub TokenError {
        display: "token validation failed",
    }
}

// Create from any error type
fn validate_token(token: &str) -> Result<(), TokenError> {
    let parsed: serde_json::Value = serde_json::from_str(token)
        .map_err(|e| TokenError { source: Box::new(e) })?;
    Ok(())
}

// Downcast to inspect the underlying error
fn handle_error(err: TokenError) {
    if let Some(json_err) = err.downcast_ref::<serde_json::Error>() {
        eprintln!("JSON parsing failed: {}", json_err);
    }
}

Example: Custom Box Type

You can specify a custom box error path if you have your own error type:

use chewie_macros::define_boxed_error;

// Assuming you have a custom BoxError type alias
type BoxError = Box<dyn std::error::Error + Send + Sync>;

define_boxed_error! {
    /// Client error with custom box type.
    pub ClientError {
        display: "client error",
        box_error_path: BoxError,
    }
}

Features

• send - Controls Send + Sync bounds in generated code. Automatically enabled by build.rs for non-browser targets (native and WASI). Browser WASM targets (wasm32-unknown-unknown) do not enable this feature.

Usage

Add to your Cargo.toml:

[dependencies]
chewie-macros = "0.1"

License

Licensed under either of:

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.