Swift bindings for the tree-sitter parsing library

What's New

Update tree-sitter and fix bug

  • Fixes bug where length of string was interpreted wrongly (#37)
  • Update tree_sitter and default languages

Swift Tree Sitter

This module provides Swift bindings for the tree-sitter parsing library


Using Swift Package Manager

Add it as a dependency in the Package.swift file.

.package(url: "https://github.com/viktorstrate/swift-tree-sitter", from: "1.0.0")

Or from Xcode navigate to File -> Swift Packages -> Add Package Dependency..., then enter this url:


Import directly to Xcode

If you want to load languages from .bundles dynamically at runtime, you'll have to import it directly to Xcode as Mac bundles aren't supported using the Swift Package Manager.

To do this, download the project and drag the folder with the SwiftTreeSitter.xcodeproj file into the sidebar of your Xcode project.


First you'll need to setup the Parser and specify what language to use.

let javascript = try STSLanguage(fromPreBundle: .javascript)
let parser = STSParser(language: javascript)

Then you can parse some source code.

let sourceCode = "let x = 1; console.log(x);";
let tree = parser.parse(string: sourceCode, oldTree: nil)!

// (program
//   (lexical_declaration
//     (variable_declarator name: (identifier) value: (number)))
//   (expression_statement
//     (call_expression function:
//       (member_expression object: (identifier)
//         property: (property_identifier))
//         arguments: (arguments (identifier)))))

Inspect the syntax tree.

let callExpression = tree.rootNode.child(at: 1).firstChild(forOffset: 0)
print("start point:\t\(callExpression.startPoint)")
print("end point:\t\(callExpression.endPoint)")
print("start byte:\t\(callExpression.startByte)")
print("end byte:\t\(callExpression.endByte)")

// type:        call_expression
// start point: STSPoint(row: 0, column: 11)
// end point:   STSPoint(row: 0, column: 25)
// start byte:  11
// end byte:    25

If your source code changes you can update the syntax tree. This will take less time than to recompute the tree from scratch again.

// replace let with const
let newSourceCode = "const x = 1; console.log(x);";

    startByte: 0,
    oldEndByte: 3,
    newEndByte: 5,
    startPoint: STSPoint(row: 0, column: 0),
    oldEndPoint: STSPoint(row: 0, column: 3),
    newEndPoint: STSPoint(row: 0, column: 5)

let newTree = parser.parse(string: newSourceCode, oldTree: tree)

Parsing text from a custom data source

If your text is stored in a custom data source, you can parse it by passing a callback to .parse() instead of a String.

let sourceLines = [
  "let x = 1;\n",

let tree = parser.parse(callback: { (byte, point) -> [Int8] in
  if (point.row >= sourceLines.count) {
    return []

  let line = sourceLines[Int(point.row)]

  let index = line.index(line.startIndex, offsetBy: Int(point.column))
  let slice = line[index...]
  let array = Array(slice.utf8).map { Int8($0) }

  return array
}, oldTree: nil)


  • Swift Tools 5.1.0
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Last updated: Fri Mar 17 2023 21:59:00 GMT-0500 (GMT-05:00)