Tree-sitter Lua

Tree-sitter Lua is a Lua 5.4 grammar for the Tree-sitter incremental parsing system. The grammar is defined in JavaScript, compiled into a C parser, and paired with an external scanner written in C for stateful string and comment rules.

The npm package remains published at v2.1.3. I developed and released the project from 2018 through 2022; it remains available under the MIT license but is not under active maintenance.

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🤝 Open-source and collaboration

• Ten GitHub releases were published between 2018 and 2022; the latest is v2.1.3.
• Three pull requests from external contributors were merged, adding named syntax nodes and return-statement improvements, per-instance scanner state, and Swift Package Manager support.
• The repository has a four-contributor history, more than 50 stars, and more than 20 forks.
• The same generated parser is available through Node.js, Rust, and Swift build configurations.

🧩 Parser design

Lua precedence and syntax-tree shape

Lua expressions combine logical, comparison, bitwise, concatenation, arithmetic, unary, and power operators. grammar.js defines their precedence explicitly and applies prec.left or prec.right according to Lua's associativity rules. Expression nodes expose named left, operator, and right fields for editor and analysis consumers.

The grammar also represents Lua 5.4 local-variable attributes, decimal and hexadecimal numerals, statements, and shebang lines. Corpus fixtures exercise these constructs alongside expression precedence.

Stateful scanning for strings and comments

Lua long strings and comments use matching delimiters such as [[...]] and [=[...]=], with a variable number of equal signs. Because the closing delimiter must match its opener, the external scanner in scanner.c tracks the active token type and delimiter depth in a per-parser payload.

The scanner serializes that two-byte state so Tree-sitter can restore it during incremental parsing. It also handles short comments, quoted strings, and escapes while keeping scanner state isolated per parser instance instead of relying on global variables.

🏗️ One parser across three ecosystems

The Tree-sitter CLI generates parser.c from grammar.js. Node.js, Rust, and Swift use different native build systems, but each binding compiles that same generated parser together with the external scanner.

grammar.js -> Tree-sitter CLI -> parser.c
                                  |
scanner.c ------------------------+
                                  |
                  +---------------+---------------+
                  |               |               |
              Node.js           Rust            Swift
              node-gyp       build.rs + cc       SwiftPM

• Node.js: the npm package exposes the generated language through a native wrapper.
• Rust: Cargo.toml and build.rs provide a crate that can be consumed from the repository.
• Swift: Package.swift compiles the C sources as a Swift Package Manager library.
• Verification: Tree-sitter corpus tests run through GitHub Actions on macOS and Ubuntu.

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🛠️ Tech stack

• Grammar: JavaScript
• Generated parser and external scanner: C
• Bindings: Node.js, Rust, Swift
• Testing: Tree-sitter corpus tests
• CI: GitHub Actions