1. Xhp LibClass libraries for XHP. XHP is a Hack feature that augments the syntax of the language such that XML document fragments become valid Hack expressions.
2. Vim HackSyntax highlighting and typechecker integration for Hack.
3. HslThe Hack Standard Library
4. Hack CodegenLibrary to programatically generate Hack code and write it to signed files
5. packagingThe sources for how we have built the HHVM packages.
8. hhastMutable AST library for Hack with linting and code migrations
11. xhp-jsEasily create JS controllers for XHP elements, and XHP wrappers for React elements