🛠️ MIDDS Types Codegen

Procedural macros for generating bounded string and collection types with Substrate and WebAssembly compatibility.

Overview

This crate provides macros to generate bounded types that work seamlessly with Substrate runtime and JavaScript bindings, solving wasm_bindgen's generic parameter limitations.

Macros

#[midds_string(bound)]

Generates bounded string types with UTF-8 validation.

use midds_types_codegen::midds_string;

#[midds_string(256)]
pub struct TrackTitle;

// With regex validation
#[midds_string(15, regex = r"^[A-Z]{2}[A-Z0-9]{3}[0-9]{2}[0-9]{5}$")]
pub struct Isrc;

// Usage
let mut title = TrackTitle::from_str("My Song").unwrap();
title.push_str(" - Extended Mix").unwrap();
assert_eq!(title.as_str(), "My Song - Extended Mix");

#[midds_collection(type, bound)]

Generates bounded collection types.

use midds_types_codegen::midds_collection;

#[midds_collection(u64, 64)]
pub struct ProducerIds;

// Usage
let mut producers = ProducerIds::new();
producers.push(12345).unwrap();
producers.push(67890).unwrap();
assert_eq!(producers.len(), 2);

Generated Features

Rust API

• Standard trait implementations (Clone, PartialEq, Encode, Decode, etc.)
• String/collection manipulation methods
• Type-specific error handling
• Substrate runtime compatibility

JavaScript API (with js feature)

• wasm_bindgen bindings
• Property getters/setters
• Type-safe method exports
• Serde serialization support

Key Benefits

• ✅ Compile-time bounds: Capacity limits enforced at compile time
• ✅ Runtime validation: UTF-8 and bounds checking at runtime
• ✅ WASM compatibility: JavaScript bindings without generic limitations
• ✅ Memory efficient: Wraps sp_runtime::BoundedVec
• ✅ Type safety: Strong typing with comprehensive error handling

Error Handling

Each generated type includes a specific error enum:

// For strings
pub enum TrackTitleError {
    InvalidUtf8,
    TooLong,
    InvalidFormat, // If regex validation is used
}

// For collections  
pub enum ProducerIdsError {
    TooManyItems,
    InvalidItem,
}

Dependencies

• proc-macro2 - Procedural macro utilities
• quote - Code generation
• syn - Rust syntax parsing