Rest provides the technical foundation TypeScript compiler within the Land project. Rest is a Rust binary that uses the OXC toolchain to compile TypeScript 2-3x faster than esbuild while producing output compatible with VS Code’s build process.

Architecture

Rest is structured as a Rust library with a binary entry point. The compilation pipeline passes source files through OXC’s parser, transformer, and code generator in sequence. An optional parallel mode processes multiple files concurrently across CPU cores.

---

Key Modules

Path	Description
`Source/Library.rs`	Binary entry point; parses CLI arguments and dispatches to compiler
`Source/Fn/OXC/Compiler.rs`	Main compilation orchestrator; coordinates parser, transformer, and codegen
`Source/Fn/OXC/Parser.rs`	Wraps `oxc_parser` with error normalization and source tracking
`Source/Fn/OXC/Transformer.rs`	Applies TypeScript-to-JavaScript AST transformations including decorators
`Source/Fn/OXC/Codegen.rs`	Generates final JavaScript text from the transformed AST
`Source/Fn/Build.rs`	Directory-based compilation: walks source trees preserving structure
`Source/Fn/Bundle/`	Bundling utilities for multi-file outputs
`Source/Fn/NLS/`	Natural Language Support string extraction
`Source/Fn/SWC/`	SWC integration shims (alternative transformer path)
`Source/Fn/Worker/`	Worker thread support for parallel compilation
`Source/Struct/CompilerConfig.rs`	Configuration struct: decorator mode, class fields, source maps
`Source/Struct/SWC.rs`	SWC-specific configuration types

Data Flow

When `--Parallel` is specified, the compiler fans out file compilation across Tokio worker threads and collects aggregated metrics.

Integration Points

Connecting Element	Direction	Mechanism	Description
Output	Consumer	Process invocation / esbuild plugin	Output’s `RestPlugin.ts` invokes the Rest binary or calls it via plugin API
Cocoon	Indirect consumer	Compiled artifacts	Cocoon loads the JavaScript produced by Rest from `Target/Microsoft/VSCode/`
Sky	Indirect consumer	`@codeeditorland/output` package	Sky loads VS Code UI components compiled through the Rest pipeline

Configuration

Option	CLI Flag / Variable	Default	Description
Input path	`--Input`	required	Directory or file to compile
Output path	`--Output`	required	Destination directory for compiled JavaScript
Parallel mode	`--Parallel`	off	Enable multi-core parallel compilation
Decorator metadata	`CompilerConfig`	`true`	Emit `emitDecoratorMetadata` for VS Code compatibility
Class fields mode	`CompilerConfig`	`false` (VS Code default)	`useDefineForClassFields` - off matches VS Code’s gulp build
Source maps	`CompilerConfig`	development only	Inline source maps for debug builds

The CompilerConfig struct is populated from either CLI flags or from the esbuild plugin context when Rest is invoked as a plugin within the Output build pipeline.