fjson

fjson is a zero-dependency JSON Parser and Fixer. It takes any input and produces valid JSON. No AI involved.

Features

Deserializes everything by default (root and nested).
Repairs incomplete JSON by closing missing brackets and strings.
Normalizes boolean and null values (e.g., True → true, FALSE → false).
Normalizes numbers (removes trailing zeros, fixes invalid formats).
Formatting (beautifier).
Zero external dependencies.

Installation

Add to Cargo.toml:

[dependencies]
fjson-core = "0.1"

API

`fix(input: impl Into<String>) -> String`

Parse and fix JSON input. Returns formatted, valid JSON.

Examples

Basic Usage

fn main() {
    let broken = r#"{ "user" "foo", "age": 0020, }"#;
    let fixed = fjson_core::fix(broken);
    println!("{}", fixed);
}

Output:

{
  "user": "foo",
  "age": 20
}

Truncated Logs

let truncated_log = r#"{"request_id": 123, "status": "success", "data": {"items": [{"id": 1}, {"id": 2}"#;
let fixed = fjson_core::fix(truncated_log);

Nested JSON Deserialization

let nested = r#"{"payload": "{\"user\": \"alice\", \"role\": \"admin\"}"}"#;
let fixed = fjson_core::fix(nested);

Output:

{
  "payload": {
    "user": "alice",
    "role": "admin"
  }
}

Use Cases

Truncated logs - Recover valid JSON from log entries that were cut off
Minified JSON - Beautify compressed JSON
Partial responses - Handle incomplete API responses
Data validation - Quick fix for malformed JSON from unreliable sources

License

This project is MIT licensed.

fjson-core 0.1.2