RJD - Rust JSON Diff

Compare JSON files or strings and output the differences. Works as a CLI tool or Rust library.

Installation

CLI:

cargo install rjd

Library:

[dependencies]
rjd = "1.2"

CLI Usage

rjd file1.json file2.json                   # changes format (default)
rjd file1.json file2.json --format rfc6902  # RFC 6902 JSON Patch format
rjd file1.json file2.json --format after    # show changed properties only
rjd file1.json file2.json --sort            # sort keys alphabetically
rjd file1.json --stdin                      # read second input from stdin
rjd '{"a":1}' '{"a":2}'                     # inline JSON

Options

• --format <FORMAT> - Output format: changes (default), rfc6902, after
• --sort, -s - Sort keys alphabetically
• --stdin - Read second input from stdin
• --ignore-json <FILE> - JSON file with paths to ignore (can be used multiple times)
• --max-file-size <SIZE> - Max file size in bytes (default: 100MB)
• --max-depth <DEPTH> - Max JSON nesting depth (default: 1000)
• --follow-symlinks - Follow symbolic links (default: reject for security)

Environment Variables

• RJD_MAX_FILE_SIZE - Default max file size
• RJD_MAX_JSON_DEPTH - Default max depth
• RJD_FOLLOW_SYMLINKS - Set to 1 to follow symlinks by default

Library Usage

use rjd::{diff, Changes};
use serde_json::json;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let old = json!({"name": "John", "age": 30});
    let new = json!({"name": "Jane", "age": 31});
    let changes = diff(&old, &new);

    // Iterate over changes
    for change in changes.modified.iter() {
        if let rjd::Change::Modified { path, old_value, new_value } = change {
            println!("{} changed from {} to {}", path, old_value, new_value);
        }
    }

    Ok(())
}

Loading Files

use rjd::{load_json_file, diff};

let old = load_json_file("old.json")?;
let new = load_json_file("new.json")?;
let changes = diff(&old, &new);

Output Formats

use rjd::create_formatter;

let formatter = create_formatter("rfc6902", false)?;
let output = formatter.format(&changes)?;

Filtering Changes

// Zero-copy filtering for large diffs
let patterns = vec!["timestamp".to_string()];
let filtered: Vec<&rjd::Change> = changes
    .iter_filtered_changes(&patterns)
    .collect();

Custom Config

use rjd::{LoadConfig, SymlinkPolicy};

let config = LoadConfig {
    max_file_size: 10_000_000,  // 10MB
    max_depth: 100,
    symlink_policy: SymlinkPolicy::Reject,
};

let json = load_json_file_with_config("data.json", &config)?;

Output Formats

Changes format (default):

{
  "added": [{"path": "email", "value": "x@y.com"}],
  "removed": [],
  "modified": [{"path": "age", "oldValue": 30, "newValue": 31}]
}

RFC 6902 format:

[
  {"op": "add", "path": "/email", "value": "x@y.com"},
  {"op": "replace", "path": "/age", "value": 31}
]

After format (final state):

{
  "name": "Jane",
  "age": 31,
  "email": "x@y.com"
}

API

Types: Change, Changes, JsonPath, RjdError, LoadConfig, SymlinkPolicy

Functions: diff(), load_json_file(), load_json_input(), create_formatter(), load_ignore_patterns()

All functions return Result<T, RjdError>.

Full docs: docs.rs/rjd

License

MIT OR Apache-2.0