Error handling

Mix.install([
  {:lua, "~> 1.0.0-rc.0"}
])

In-band recovery with pcall

Lua’s pcall returns false, message instead of propagating an error, so scripts can recover from failures in-band.

{[ok?, message], _lua} =
  Lua.eval!(Lua.new(), ~S[return pcall(function() error("something broke") end)])

{ok?, message}

{false, "something broke"}

Inspecting a structured exception

When an error escapes a script, Lua.eval!/2 raises Lua.RuntimeException with :line, :source, and :call_stack populated. Pass source: so the attribution names your script.

try do
  Lua.eval!(
    Lua.new(),
    """
    local user = nil
    return user.name
    """,
    source: "profile.lua"
  )
rescue
  e in Lua.RuntimeException ->
    IO.inspect(e.source, label: "source")
    IO.inspect(e.line, label: "line")
    IO.puts(Exception.message(e))
end

source: "profile.lua"
line: 2
Lua runtime error: Runtime Type Error

  at profile.lua:2:

  attempt to index a nil value (local 'user')


Suggestion:
  You can only index tables. Make sure the value you're indexing is a table, not a nil.