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title = fig
version = 2.0.0
author = adammharris
created = 2026-05-08
updated = 2026-07-05T21:46:34-06:00
contents = [[fig docs](docs/docs.md)]
fig is a Zig library for parsing and editing config files.
Originally made for Diaryx, fig allows editing frontmatter in markdown files without reserializing the data, preserving comments and other trivia. fig has since been expanded to include many different kinds of configuration formats and different kinds of embedding.
It currently supports the following formats:
- YAML (1.2.2 and 1.1)
- JSON (strict, JSONC, JSON5)
- TOML (1.1 and 1.2)
- ZON (Zig Object Notation)
- XML (experimental, not included by default)
- Fig (.figl), an in-house authoring dialect authored by yours truly!
And you can use fig in the following programming languages:
- Zig
- Rust
- Typescript (experimental)
- C (not tested, but likely works)
Command-line interface
Download from Github Releases or with Homebrew:
Or run it with no install at all (needs Node 20+; experimental — see docs/npm-wasi.md):
Run fig help for instructions for how to use it on your files.
Planned features
- Better testing for the Typescript bindings
- Styling directives (maintain styling across formats, such as mapping TOML inline->YAML inline)
- More distribution options (package managers, etc.)
- More bindings
- Advanced filtering/querying capabilties ("convert to this format, except without this node")
Fine print
Contibutions
Contributions are welcome, subject to my approval.
AI Use
fig, like many deceptively simple systems-level codebases, require careful thought and intention. AI tools can generate code rapidly, often at the cost of this important design thinking. Therefore, I have chosen to limit the use of AI code generation in this codebase.
I started writing this library by hand (no AI) for my own education, and for use in my larger project, Diaryx. After writing a JSON tokenizer and parser by hand, and designing the Document, Token, and Language abstractions, I decided to make use of the Codex AI tool to generate specific portions of the code that would otherwise require hours of tedious, repetitive work.
Using Codex, I was able to make a compliant YAML parser much faster than I would have been able to otherwise. Later, I used Claude Code to do the same for TOML, ZON, and JSON5. For each of these, I made a conformance suite in order to ensure a correct implementation.
All of the code generated was carefully reviewed and edited according to my taste before being accepted. I take full responsibility and ownership of the code in this repository. If you have any questions or concerns about AI use in this project, please contact me!
License
MIT or Apache 2.0, at your discretion. If you use fig in your work, I would love to hear from you and feature you here! Please contact me!
Credits
I took the JSON test suite at testdata/json from Nicolas Seriot's JSONTestSuite repository. I'm grateful that it is licensed under the MIT license, so I am allowed to use it for fig. A copy of the license is included in this repository at testdata/json/LICENSE.
Likewise, test suite licenses are included for JSON5, TOML, and YAML. I am thankful for each of them.
I am also thankful for the toml-edit Rust crate, which provided inspiration for the complex structural edits required by any format-preserving TOML editor.
Contact Me
amh421@icloud.com, or leave an issue.