fs-extra is a Node.js library that extends the native `fs` module with additional file system operations and promise support. It provides drop-in replacement for `fs` with methods like `copy`, `move`, `remove`, `ensureDir`, `outputFile`, `readJson`, `writeJson`, and more. The library uses `graceful-fs` to prevent EMFILE errors and `universalify` to add promise support to all async methods. It supports both CommonJS and ESM imports. The codebase is well-structured with separate modules for each feature (copy, move, ensure, json, mkdirs, etc.) and comprehensive test coverage. It handles edge cases such as symlinks, permissions, timestamps, cross-device moves, and case-insensitive file systems. The library is actively maintained with frequent releases and supports Node.js 14+.
Union is a hyper-efficient zero-knowledge infrastructure layer for cross-chain interoperability, implementing IBC (Inter-Blockchain Communication) with light clients for Cosmos, Ethereum, Sui, StarkNet, Gno, and many other chains. The system comprises a Cosmos SDK blockchain (uniond), a zero-knowledge prover (galoisd) for Groth16 proofs, a modular relayer (voyager) with plugin-based architecture, CosmWasm smart contracts for IBC and asset transfers (UCS03), EVM Solidity contracts, and a TypeScript SDK for programmatic interaction. The frontend is a Svelte 5 application (app2) providing a transfer interface, explorer, dashboard, and staking UI, while documentation is served via an Astro site. The architecture is a multi-language monorepo with Rust as the dominant language for core libraries and relayer modules, Go for the Cosmos SDK chain and prover, TypeScript for SDKs and frontend, and Solidity/Move for smart contracts. Key design patterns include a trait-based light client interface (IbcClient), a plugin system for relayer modules (voyager_sdk), functional effect management in TypeScript (Effect-TS), and derive macros for encoding (model, ssz, ethabi). The codebase demonstrates high craftsmanship in its type-safe encoding primitives, storage abstractions (depolama), and persistent queue (pg-queue), though it suffers from some code duplication across SDK versions and generated protobuf drift risks.