rnix-parser

rnix is a parser for the Nix language written in Rust.

This can be used to manipulate the Nix AST and can for example be used for:

• Interactively render Nix on a GUI
• Formatting Nix code
• Rename identifiers

and a lot more!

rnix nowadays uses @matklad's rowan crate to ensure:

• all span information is preserved, meaning you can use the AST to for example apply highlighting
• printing out the AST prints out 100% the original code. This is not an over-exaggeration, even completely invalid nix code such as this README can be intact after a parsing session (though the AST will mark errnous nodes)
• easy ways to walk the tree without resorting to recursion

Demo

Examples can be found in the examples/ directory.

You may also want to see nix-explorer: An example that highlights AST nodes in Nix code. This demonstrates how whitespaces and commands are preserved.

Hacking

Tests can be run with cargo test.

In order to update all .expect-files to the currently expected results, you may run UPDATE_TESTS=1 cargo test.

You can parse Nix expressions from standard input using the from-stdin example. To try that, run the following in your shell:

echo "[hello nix]" | cargo run --quiet --example from-stdin

Release Checklist

• In CHANGELOG.md, add a ## [vX.Y.Z] - YYYY-MM-DD heading below ## [Unreleased], add a [vX.Y.Z] compare link at the bottom, and point the [Unreleased] link at vX.Y.Z...master.
• Bump version in Cargo.toml.
• Refresh the lockfiles: cargo update -w && cargo update -w --manifest-path fuzz/Cargo.toml.
• Run cargo test, nix build and cargo publish --dry-run.
• Commit as chore: release vX.Y.Z on a branch, open a PR, and add it to the merge queue.
• Once it merges, tag the release commit vX.Y.Z and push the tag.
• Approve the release workflow run the tag started. It checks that the tag is on master and matches Cargo.toml, publishes to crates.io, and creates the GitHub release from the changelog section.
• Check the new version on crates.io and the GitHub release.

RIP jd91mzm2

Sadly, the original author of this project, @jD91mZM2 has passed away. His online presence was anonymous and what we have left is his code. This is but one of his many repos that he contributed to.