What is cosmo?

Cosmo is a templating engine for the Lua programming language that lets you fill in placeholder values in text templates safely. The key benefit is that it provides much of the flexibility of full-powered template systems without the security risks that come from letting templates run arbitrary code. In many template systems, the template itself can contain programming logic, which means anyone who writes or edits a template could potentially run harmful code on your system. Cosmo avoids this by design. It supports nested templates, expressions, and subtemplates, but keeps the template language restricted so it cannot execute arbitrary commands. This makes it suitable for situations where templates might be user-generated or where you want to keep presentation logic safely separated from application logic. You would use Cosmo if you are building an application in Lua that needs to generate dynamic text, such as HTML pages, configuration files, emails, or reports, and you want to let people design or customize those templates without giving them the keys to your entire system. For example, if you are running a web application and want to allow users to theme their own pages, a safe template engine lets them control layout and content without risking a security hole. The project is installed as a Lua "rock," which is the standard package format for Lua libraries. It requires a C compiler toolchain on UNIX-based systems. The README does not go into detail on usage specifics or advanced configuration, it mainly notes that the current version adds support for Lua 5.3 and lists a few historical bug fixes and feature additions from prior releases.