rnix

rnix is a Nix parser 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 ...

• will always maintain span information (byte offset in the string) so the error messages can be as useful as possible and any syntax highlighting plugin could use the tokenizer to highlight.
• will preserve ALL syntax. Printing out the AST must print out the original file - and if it doesn't that's a bug. (Thank @matklad for the design ideas and motivation!)
• works on top of Rust iterators, which are lazy by design. You get cool functions like map and filter at your fingertips!

Demo

Examples can be found in the examples/ directory.

You may also want to see nix-explorer: An example that highlights AST nodes in valid Nix code. This demonstrates how span information is preserved.

Unimplemented

I have implemented everything I can think of. Most, if not all of these, are tested inside the tests/ directory. If some kind of syntax isn't tested there, you should report it as unimplemented.