JSONCKit

A lightweight Swift package that converts JSONC (JSON with Comments) to standard JSON.

• Zero dependencies
• Single-pass, length-preserving conversion
• Lenient — malformed input is passed through for downstream parsers to handle
• Swift 6 strict concurrency ready

Features

• Strip single-line comments (// ...)
• Strip multi-line comments (/* ... */)
• Remove trailing commas in objects and arrays

Installation

Add JSONCKit to your Package.swift:

dependencies: [
    .package(url: "https://github.com/steelbrain/JSONCKit.git", from: "1.0.0"),
]

Then add it as a dependency to your target:

.target(
    name: "YourTarget",
    dependencies: ["JSONCKit"]
),

Usage

Convert a JSONC string to JSON

import JSONCKit

let jsonc = """
{
    // Database settings
    "host": "localhost",
    "port": 5432,
    /* Credentials */
    "user": "admin",
}
"""

let json = JSONC.convert(jsonc)
// json is now valid JSON with comments and trailing comma removed

Convert JSONC Data to JSON Data

let jsoncData: Data = ...
let jsonData = try JSONC.convertToData(jsoncData)

Decode a Decodable type directly

struct Config: Decodable {
    let host: String
    let port: Int
    let user: String
}

let config = try JSONC.decode(Config.self, from: jsoncData)

API

Method	Signature	Description
convert	(String) -> String	Convert a JSONC string to JSON
convertToData	(Data, encoding:) throws -> Data	Convert JSONC data to JSON data
decode	(T.Type, from:encoding:decoder:) throws -> T	Decode a Decodable type from JSONC data

How it works

The converter makes a single pass over the input bytes, replacing comments and trailing commas with whitespace. The output is always the exact same byte length as the input, so downstream parsers report correct line and column positions for any errors they find.

Attributions

See ATTRIBUTIONS.md for implementation and test suite references.

License

MIT — see LICENSE for details.