How to debug moonscript?

Question

I trying to write some game, based on Love2d framework, compiled from moonscript. Every time when I make a mistake in my code, my application throws error and this error refers to compiled lua-code, but not a moonscript, so I have no idea where exactly this error happens. Tell me please, what a solution in this situation? Thanks.

Answer 1

Moonscript does support source-mapping/error-rewriting, but it is only supported when running in the moon interpreter: https://moonscript.org/reference/command_line.html#error_rewriting

I think it could be enabled in another lua environment but I am not completely sure what would be involved.

It would definetely require moonscript to hold on to the source-map tables that are created during compilation, so you couldn't use moonc; instead use the moonscript module to just-in-time compile require'd modules:

main.lua

-- attempt to require moonscript,
-- for development
pcall(require, 'moonscript')

-- load the main file
require 'init'

init.moon

love.draw = ->
  print "test"

with this code and moonscript properly installed you can just run the project using love . as normal. The require 'moonscript' call will change require to compile moonscript modules on-the-fly. The performance penalty is negligible and after all modules have been loaded there is no difference.

Answer 2

Debugging is a problem for pretty much any source-to-source compilation system. The target language has no idea that the original language exists, so it can only talk about things in terms of the target language. The more divergent the target and original languages are, the more difficult debugging will be.

This is a big part of the reason why C++ compilers don't compile to C anymore.

The only real way to deal with this is to become intimately familiar with how the Moonscript compiler generates Lua from your Moonscript code. Learn Lua and carefully read the output Lua, comparing it to the given Moonscript. That will make it easier for you to map the given Lua error and source code to the actual Moonscript code that created it.