lua-features

lua-features is a static analyser for lua. It can parse code in Lua 5.1, 5.2, 5.3 and LuaJIT. Its code is adapted from luaparse.

Features

On top of interpreting usual Lua, it is also a transpiler that can add additional features on top of the language. All features are then transpiled to plain lua (see CLI). Current features are:

Const variables

Wherever you could use local (variable or function declaration) you can instead use const, this ensures that such variable cannot be reassigned.

const x = 1
x = 2 -- error: cannot reassign a constant
function x() end -- error: cannot reassign a constant

Type checking

This feature is experimental and does not work properly, avoid using it. The plan is to add static type checking to lua, like flow and TypeScript do to Javascript.

local x : number = 1;
x = "1" -- error: cannot assign string to number
function add(x, y: number, number): number
    return x + y
end
add(1, 'a') -- error: cannot call function

Command line interface

lua-features provides a CLI (see the code). Use the help command to get instructions.

lua-features <command>

Commands:
  lua-features check <src-dir>              Check all .lua files in src-dir.
  lua-features transpile <src-dir>          Transpile all .lua files in src-dir
  <out-dir>                                 to out-dir

Options:
  --version  Show version number                                       [boolean]
  --help     Show help                                                 [boolean]

The check command tries to compile all files in a directory:

lua-features check <src-dir>

Check all .lua files in src-dir.

Positionals:
  src-dir  Input directory                                   [string] [required]

Options:
  --version         Show version number                                [boolean]
  --help            Show help                                          [boolean]
  --type-check, -t  Enables type-checking.                             [boolean]
  --const, -c       Enable const variables.                            [boolean]
  --with-lua, -l    Lua version to be compatible with.
                          [choices: "5.1", "5.2", "5.3", "JIT"] [default: "5.1"]

This will print nicely formatted errors if your files don't compile.

# example.lua:
const x = 1;
x = 2;

# cli
lua-features check . --const

# output
[.//example.lua:2:1-6] cannot reassign a constant
    x = 2;
    ^^^^^

The transpile command transpiles all files from one directory to plain lua, and copies them to another directory.

lua-features transpile <src-dir> <out-dir>

Transpile all .lua files in src-dir to out-dir

Positionals:
  src-dir  Input Directory                                   [string] [required]
  out-dir  Output directory                                  [string] [required]

Options:
  --version         Show version number                                [boolean]
  --help            Show help                                          [boolean]
  --type-check, -t  Enables type-checking.                             [boolean]
  --const, -c       Enable const variables.                            [boolean]
  --with-lua, -l    Lua version to be compatible with.
                          [choices: "5.1", "5.2", "5.3", "JIT"] [default: "5.1"]

If you're using the const feature, for example, all consts are changed to local. Notice it transpiles even if check errors for some feature. The spacing is messed up for now, but may be fixed in the future. I tried to keep at least the same line numbers for all operations, that way if you get an error on line X in your transpiled code, it surely came from line X in the original code. The transpile example.lua file looks like:

local  a = 1
 a = 2

Contributions

I accept PR's!

However, I will not lie: I'm not sure how much more time I'm gonna spend improving this repository :)

Possible feature ideas:

• Compatibility: for example, compile Lua 5.3 bitops to use LuaJIT bit library.
• continue: continue can probably be transpiled to some goto's