Liaise

Liaise is a no_std diagnostic framework that enforces unique error identities at compile-time. It provides a bridge (a "liaison") between your internal error enums and professional, grep-able diagnostic reporting.

Why Liaise?

1. Introspection & Validation: Automatically extracts variant IDs and ensures no two variants share the same ID.
2. Zero-Runtime Cost: All validation happens during compilation via a "Sentinel" check. If your IDs aren't unique, the code won't build.
3. Enterprise Standards: Standardizes error reporting into the [PREFIX0000] format used by professional toolchains.
4. Proc-macro Ready: Includes built-in adapters for syn and proc-macro2 for high-quality compiler error reporting.

Quick Start

1. Define and Register

Use #[derive(RegisterErrors)] to turn a standard enum into a validated Registry.

use liaise::{Liaise, RegisterErrors};

#[derive(RegisterErrors)]
#[error_prefix = "FILE"] // Sets the reporting prefix
pub enum FileError {
    NotFound = 404,
    PermissionDenied = 403,
    // Duplicate = 404, // THIS WOULD TRIGGER A COMPILE ERROR
}

impl Liaise for FileError {
    fn code_id(self) -> u16 { self as u16 }
    
    fn message(self) -> &'static str {
        match self {
            Self::NotFound => "The requested file was not found.",
            Self::PermissionDenied => "Access to this file is restricted.",
        }
    }
}

2. Batch Reporting (with syn)

If you're writing a procedural macro, use the DiagBuffer to collect errors and report them all at once.

use liaise::adapters::syn_impls::{SynBuffer, SynBufferExt};

fn validate_tokens(input: MyAst) -> syn::Result<()> {
    let mut buffer = SynBuffer::new();

    if input.is_invalid() {
        // Automatically renders as: [FILE0404] The requested file was not found.
        buffer.push_at(input.span(), FileError::NotFound);
    }

    buffer.finish() 
}

The Architecture

Liaise splits diagnostic concerns into three layers to maintain no_std purity and modularity:

Features

• syn-error: Enables the SynBuffer and helper extensions for syn.

Pro-Tip: Stability is Key

Liaise is designed for systems where error codes are permanent. By assigning an explicit u16 to every variant, you ensure that even if you rename the variant in your source code, the error ID remains stable for your users, documentation, and support teams.