bigcrush / lua-parser

A Lua 5.3 parser written with LPeg

lua-parser

This is a Lua 5.3 parser written with LPeg that generates an AST in the format specified by Metalua. The parser also implements an error reporting technique that is based on tracking the farthest failure position.

Requirements

    lua >= 5.1
    lpeg >= 0.12

API

The package lua-parser has two modules: lua-parser.parser and lua-parser.pp.

The module lua-parser.parser implements the function parser.parse:

• parser.parse (subject, filename)

  Both subject and filename should be strings. It tries to parse subject and returns the AST in case of success. It returns nil plus an error message in case of error. In case of error, the parser uses the string filename to build an error message.

The module lua-parser.pp implements a pretty printer to the AST and a dump function:

• pp.tostring (ast)

  It converts the AST to a string and returns this string.

• pp.print (ast)

  It converts the AST to a string and prints this string.

• pp.dump (ast[, i])

  It dumps the AST to the screen. The parameter i sets the indentation level.

Usage

Code example for parsing a string:

local parser = require "lua-parser.parser"
local pp = require "lua-parser.pp"

if #arg ~= 1 then
    print("Usage: parse.lua <string>")
    os.exit(1)
end

local ast, error_msg = parser.parse(arg[1], "exemplo1.lua")
if not ast then
    print(error_msg)
    os.exit(1)
end

pp.print(ast)
os.exit(0)

Running the above code example using a string without syntax error:

$ lua parse.lua "for i=1, 10 do print(i) end"
{ `Fornum{ `Id "i", `Number "1", `Number "10", { `Call{ `Id "print", `Id "i" } } } }

Running the above code example using a string with syntax error:

$ lua parse.lua "for i=1, 10 do print(i) "
exemplo1.lua:1:24: syntax error, unexpected 'EOF', expecting 'end',
'return', 'Name', 'goto', 'break', '::', 'local', 'function', 'repeat',
'for', 'do', 'while', 'if', ';', '=', ',', 'String', '{', '(', ':', '[', '.'