Lua doesn't directly support keyword arguments, but you can simulate it using tables:

    serialize(someObject, { prettyPrint = true })

And indeed that is a big improvement (and commonly done), but it doesn't solve all problems. Say you have X flags, then there's 2^X different configurations you have to check and test and so forth. In reality, all 2^X configurations will not be used, only a tiny fraction will be. In addition, some configurations will simply not be legal (i.e. if flag A is true, then flag B must be as well), and then you have a "make illegal states unrepresentable" situation.

If the tiny fraction is small enough, just write different functions for it ("serialize()" and "prettyPrint()"). If it's not feasible to do it, have a good long think about the API design and if you can refactor it nicely. If the number of combinations is enormous, something like the "builder pattern" is probably a good idea.

It's a hard problem to solve, because there's all sorts of programming principles in tension here ("don't repeat yourself", "make illegal states unrepresentable", "feature flags are bad") and in your way of solving a practical problem. It's interesting to study how popular libraries do this. libcurl is a good example, which has a GAZILLION options for how to do a request, and you do it "statefully" by setting options [1]. libcairo for drawing vector graphics is another interesting example, where you really do have a combinatorial explosion of different shapes, strokes, caps, paths and fills [2]. They also do it statefully.

[1]: https://curl.se/libcurl/c/curl_easy_setopt.html

[2]: https://cairographics.org/manual/cairo-cairo-t.html