Lua

Lesson 09

Configuration validation

Validate Lua configuration tables before using them to build routes, plugins, or runtime behavior.

Good Code

src/config.lua
local function read_config(config)
  assert(type(config) == "table", "config must be a table")
  assert(type(config.review_path) == "string", "review_path must be a string")

  -- Validated config returns a predictable shape to runtime code.
  return {
    review_path = config.review_path,
    max_reviews = tonumber(config.max_reviews) or 100,
  }
end

Bad Code

config.lua
local function read_config(config)
  -- Runtime code receives whatever shape the config file happened to define.
  return config
end

Review Notes

What to review

Good Code

The good version checks that the config is a table and that required fields have the expected type. Runtime code receives a normalized shape.

Bad Code

The bad version passes the raw config table through. Typos and wrong types fail later, often far away from the file that introduced them.

Takeaways

  • Lua config review should check required fields and value types at load time.