Rodar Lua

Lua script engine adapter for Rodar.

Enables Lua scripts in BPMN <scriptTask> elements by implementing the Rodar.Expression.ScriptEngine behaviour. Uses Luerl — a Lua 5.3 implementation in pure Erlang — as the runtime. No NIFs or external processes required.

Installation

Add to your mix.exs:

{:rodar_lua, "~> 0.1.0"}

Quick Start

# In your Application.start/2 callback:
Rodar.Expression.ScriptRegistry.register("lua", RodarLua.Engine)

Then use scriptFormat="lua" in your BPMN diagrams:

<scriptTask id="calc" name="Calculate Total" scriptFormat="lua">
  <script>return price * quantity</script>
</scriptTask>

The current process data map is injected as Lua globals. The script's first return value is stored in the process context under the :script_result key by default, or a custom key when the task specifies output_variable.

Usage

Call the engine directly for ad-hoc evaluation:

{:ok, 3} = RodarLua.Engine.eval("return 1 + 2", %{})

{:ok, "hello"} = RodarLua.Engine.eval("return greeting", %{"greeting" => "hello"})

{:ok, 10} = RodarLua.Engine.eval("return data.count * 2", %{
  "data" => %{"count" => 5}
})

Data Marshalling

Elixir values are automatically converted to Lua and back:

Elixir	Lua	Notes
integer / float	number	whole-number floats recovered as integers
binary (string)	string
boolean	boolean
nil	nil
map	table	keys stringified; nested maps supported
list	table	1-indexed; sequential-key tables → lists
atom key	string key	atom keys converted via `to_string/1`

Sandboxing

Scripts execute in a sandboxed Lua state. The following standard library functions are removed before execution to prevent untrusted scripts from accessing the host system:

io — all file/console I/O
file — file system access
os.execute, os.exit, os.getenv, os.remove, os.rename, os.tmpname
require, load, loadfile, loadstring, dofile, package

Safe functions like string, table, math, os.time, os.date, os.clock, os.difftime, tonumber, tostring, type, pairs, ipairs, select, unpack, pcall, and xpcall remain available.

Configuration

All settings are optional:

config :rodar_lua,
  max_time: 5_000,         # sandbox timeout in ms (default: 5_000)
  max_reductions: :none    # reduction limit (default: :none)

Development

mix deps.get          # Install dependencies
mix compile           # Compile the project
mix test              # Run all tests
mix format            # Format code

License

Apache-2.0 — see LICENSE.