Donna now has a Tree-sitter grammar

Donna now has a tree-sitter grammar. That means better editor support, smarter highlighting, and a foundation for building real tooling around the language.

What's a tree-sitter parser?

Tree-sitter is a parser generator tool and an incremental parsing library. It builds a concrete syntax tree for a source file and efficiently updates that tree as the file is edited. The key word is incremental — it does not re-parse the whole file on every keystroke. It only re-parses what changed. That makes it fast enough to run in real time inside an editor.

Most language support in editors today is built on regular expressions. Regex-based grammars are fast to write but they break easily. Strings that look like keywords get colored as keywords. Comments inside strings get parsed as code. Tree-sitter does not have these problems because it actually understands the structure of the code.

What this means for Donna

Before this, editors had no understanding of Donna files. You could write a .donna file and at best get generic text coloring. Now, editors that support tree-sitter — Zed, Neovim, Helix, Emacs, and others — can properly highlight Donna code. Functions are colored as functions. Types as types. Module paths as namespaces. Pattern variables as parameters. The editor sees the same structure the compiler sees.

Editor support

The Zed extension for Donna already uses this grammar and is available at zed-donna. A Visual Studio Code extension is also available at vscode-donna, using the grammar compiled to WebAssembly to power semantic token highlighting directly inside VS Code.

We intent to add more editor support as Donna grows.

What's next

The grammar covers the full Donna syntax as it stands today. As the language evolves, the grammar will follow. The tree-sitter-donna repository is open and contributions are welcome.

If you build something on top of it — a plugin, a highlight theme, a query file — let us know on GitHub.