An out-of-box Lua parser written in Lark

Such parser handles a relaxed version of Lua 5.3 grammar.

This is a Python-Lark implementation of Lua 5.3 parser. It has the following features:

  1. the grammar is compatible to LALR(1)/LR(1)/ALL(*)
  2. the generated parser creates declarative and typed Python dataclasses instead of error-prone CSTs — that’s why we call it “out-of-box”.

Fable.Sedlex, which is an F# port of OCaml sedlex project and transpiled into Python, is used in this parser to achieve high-quality lexer that avoids unnecessary collisions of lexical rules.


This project serves as a control group of comparisons against Typed BNF. We tend to show the conciseness, declarativity, simplicity, and other advantages of TypedBNF.


It supports full lua 5.3 syntax except

  1. assignment left-hand side can take arbitrary expressions, which is invalid in real lua syntax. This can be checked after parsing.

  2. support for nested literal strings is limited: only [[...]], [[=]], [=[...]=] are correctly supported.

  3. comments support only -- ... form, i.e., line comments.

Stats of non-generated part

Stats by term counter

file characters lines description
lua.lark 3979 123 define grammar 4172 228 define ASTs 599 27 define necessary operations
to construct ASTs


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