MoonScript Configuration Syntax

Configuration Example

The MoonScript configuration builder syntax uses function calls to define variables. The advantage to this approach over using a Lua table literal is that you can have logic surrounding your assignments. You can also freely mix regular table objects.

Here’s an example of the configuration DSL (domain specific language) and the table it generates:

config = require "lapis.config"

some_function = -> steak "medium_well"

config "development", ->
  hello "world"

  if 20 > 4
    color "blue"
  else
    color "green"

  custom_settings ->
    age 10
    enabled true

  -- tables are merged
  extra ->
    name "leaf"
    mood "happy"

  extra ->
    name "beef"
    shoe_size 12

    include some_function


  include some_function

  -- a normal table can be passed instead of a function
  some_list {
    1,2,3,4
  }

  -- use set to assign names that are unavailable
  set "include", "hello"

Which generates the following table:

{
  hello: "world"
  color: "blue"

  custom_settings: {
    age: 10
    enabled: true
  }

  extra: {
    name: "beef"
    mood: "happy"
    shoe_size: 12
    steak: "medium_well"
  }

  steak: "medium_well"

  some_list: { 1,2,3,4 }

  include: "hello"
}

Names that are already global variables in Lua, like type or table, can’t be set by calling them because the global is found instead. The same applies to the special functions set, unset, and include. Use set to assign values with these names.

unset removes values that were set by a previous configuration:

config "production", ->
  unset "custom_settings", "extra"

Tables with named keys are merged key by key. Arrays are not merged: an array replaces any existing value, so setting {9} on top of {1, 2, 3} results in {9}, and setting {} clears the array. An error is thrown for a table with both array items and named keys, or an array with missing (nil) values.