Hygen vs TypeSpec

Hygen is a free, open-source code generator that runs in a project and creates code from templates. Its generators are self-contained, with folder structure defining the commands, and it looks for a local `_templates` directory so templates can stay beside project code. Built-in scaffolds help create generators, including through prompts. Templates use EJS and frontmatter, where a `to` value can set the generated file destination. Generators accept command-line arguments, interactive or multi-step prompts, file creation, and content injection into existing files. Templates can also run shell commands, while actions can select matching files with strings or regular expressions. A documented `--dry` option supports test-running generators. Hygen was built for React, Redux, and Node.js boilerplate but can be used with any technology. It runs on Linux, macOS, and Windows, is MIT licensed, and is distributed through Homebrew, npm, Yarn, npx, and standalone binaries.

TypeSpec is a language for defining API shapes and data models, then producing schemas, API specifications, code, and documentation. Its standard library supports OpenAPI 3.0, JSON Schema 2020-12, and Protobuf. OpenAPI output can feed tools for API gateways, code generation, and validation; JSON Schema output can be used to validate data built from shared models. The HTTP library’s `@useAuth` decorator lets authors attach documented security schemes—including HTTP authentication, API keys, OAuth2, and OpenID Connect—to services, interfaces, or operations. Editor support for Visual Studio Code and Visual Studio includes syntax help and completion; the VS Code extension adds diagnostics, formatting, quick fixes, refactoring, and documentation preview. Users can extend TypeSpec with emitters and decorators. The CLI is available through npm for Node.js or as an experimental standalone executable, and a browser playground is available. TypeSpec is open source and free: free. Its emitter framework is experimental, and client emitters for JavaScript, Python, Java, and C# are in preview.