Board Thread:Lua Help/@comment-24473195-20150504194158/@comment-11733175-20150531110705

ParserFunctions aren't transcluded per se, they're not really templates. They're designed for relatively simple logic and often power templates rather than being templates themselves. There's a similar learning curve for PF and Lua, they both require looking up documentation to learn and use and I'd argue that they're actually a very basic programming language (despite mediawiki devs doing their best to resist wikitext being such).

Lua is actually pretty well documented, it has a large manual online and there's lots of examples made by the community. The mediawiki libraries could use a little more love where the docs are concerned, but that'll come in time. I don't believe there's anything to automatically generate the docs quite yet so they're a bit behind the JS or PHP documentation wikimedia host at the moment.

People re-invent code all the time in many languages. It's not uncommon for wikis to have subtly or hugely different templates for the same purpose because they had different needs and different people writing them. It's frustrating when it comes to Lua (largely due to it's lacking standard library), but it's not a huge obstacle.