Z-TOON

A Zig parser implementation of the TOON (Token-Oriented Object Notation) format.

What is TOON?

TOON is a line-oriented, indentation-based text format that encodes the JSON data model with explicit structure and minimal quoting. It's particularly efficient for arrays of uniform objects, providing a more compact and readable alternative to JSON for structured data.

See the full specification for details in depth.

Features

Core Encoding/Decoding: Full JSON ↔ TOON conversion
Primitives: strings, numbers, booleans, null with smart quoting
Objects: Nested objects with indentation-based structure
Arrays: Both inline (primitives) and multi-line (objects/nested)
Tabular Arrays: Compact [N]{field1,field2}: format for uniform object arrays
Alternative Delimiters: Comma (default), tab (\t), and pipe (|) support
Delimiter Detection: Automatic delimiter detection in array headers [N<delim>]
CLI Tool: Encode and decode via command line or pipes

Usage

The project provides both a simple CLI for JSON to TOON conversion and vice versa, and its library.

Status & Roadmap

Implemented ✅

Core TOON encoder and decoder
Nested objects with indentation
Tabular arrays with field lists
Alternative delimiters (comma, tab, pipe)
Delimiter detection from array headers
Smart string quoting
CLI tool
Field order preservation (deterministic output)
Comprehensive error messages with line/column information

Planned 📋

Key folding (keyFolding="safe" mode) - collapse single-key object chains into dotted notation
Path expansion (expandPaths="safe" mode) - split dotted keys into nested objects
Strict mode validation (length mismatches, malformed headers)
Conformance test suite from spec/tests/fixtures/
Performance optimizations
Benchmarks vs JSON

Known Limitations ⚠️

Some edge cases from spec may not be fully covered
Non-strict mode has limited validation

Next Steps

To continue improving this implementation:

Strict Mode: Implement validation for length mismatches, invalid characters, and malformed headers
Key Folding: Implement optional keyFolding="safe" mode for dotted-path notation
Path Expansion: Implement optional expandPaths="safe" mode for splitting dotted keys
Better Delimiters: Auto-select optimal delimiter on encode based on content analysis
Performance: Profile and optimize hot paths, especially for large tabular arrays

Testing

Testing depends on the specification submodule fixtures.

README