yoshi-derive

Derive macros for automatically generating Yoshi error types. Because writing error boilerplate is boring.

What's this?

Generates std::error::Error implementations, Display, and conversion to Yoshi types automatically.

Installation

[dependencies]
yoshi-derive = "0.1"
yoshi = "0.1"

Basic Usage

use yoshi_derive::YoshiError;

#[derive(Debug, YoshiError)]
pub enum MyError {
    #[yoshi(display = "User {user_id} not found")]
    #[yoshi(kind = "NotFound")]
    UserNotFound { user_id: u32 },

    #[yoshi(display = "Failed to parse config: {source}")]
    ParseError {
        #[yoshi(source)]
        source: std::io::Error,
        #[yoshi(context = "config_file")]
        path: String,
    },
}

Attributes

Container Attributes (#[yoshi(...)] on enums)

Variant Attributes (#[yoshi(...)] on enum variants)

Field Attributes (#[yoshi(...)] on struct fields)

Advanced Example

use yoshi_derive::YoshiError;

#[derive(Debug, YoshiError)]
#[yoshi(error_code_prefix = "DB")]
#[yoshi(default_severity = 75)]
pub enum DatabaseError {
    #[yoshi(error_code = 1001)]
    #[yoshi(display = "Connection to {host}:{port} failed")]
    #[yoshi(kind = "Network")]
    #[yoshi(severity = 120)]
    #[yoshi(transient = true)]
    ConnectionFailed {
        host: String,
        port: u16,
        #[yoshi(source)]
        cause: std::io::Error,
        #[yoshi(context = "connection_timeout")]
        timeout: std::time::Duration,
    },

    #[yoshi(error_code = 2001)]
    #[yoshi(display = "Query failed: {query}")]
    #[yoshi(kind = "Internal")]
    QueryFailed {
        query: String,
        #[yoshi(shell)]
        execution_stats: QueryStats,
    },
}

#[derive(Debug)]
struct QueryStats {
    duration_ms: u64,
    rows_affected: usize,
}

Generated Code

The derive macro automatically creates:

• std::fmt::Display implementation
• std::error::Error implementation
• From<YourError> for yoshi_std::Yoshi conversion
• Error code and severity methods

Smart Inference

The macro automatically infers attributes based on naming:

• timeout, expired → kind = "Timeout"
• network, connection → kind = "Network"
• not_found, missing → kind = "NotFound"
• std::io::Error fields → source = true

Performance

• Compilation: <100ms for typical enums (<50 variants)
• Runtime: Zero overhead - generates efficient code
• Memory: Uses static strings where possible

License

Licensed under either of Apache License, Version 2.0 or MIT License at your option.