Here is a list of thing which are possibly necessary for end-users (found by polling random template writers):
- String functions and regular expressions — requested by most users whom I asked. Essentially one of the reasons why we want scripting language at all.
- Proper error reporting. If an error occurred on certain wiki page, there should be a traceback which lists all modules and the line on which the error occurred.
- Image output.
TODO: ask more users. Open a village pump discussion about that.
Here is a list of things we would probably want to do as well:
- Global scripts
- Code editor
- Debugging tools
Here are potential implementation obstacles:
- Lua has a feature called "pattern matching". This is essentially a regular expressions, but with their own special features. They are not Perl-compatible unlike what most of Wikipedia use.
- Image output sounds like something that has a rather low priority.
- Lua seems to have issues with error handling. Apparently it does not have proper exceptions.
- The main issue with global scripts is to invalidate the cache on local wikis when a global script is changed.
- Lua is on bad terms with Unicode. See http://lua-users.org/wiki/LuaUnicode.