Editor Support

Chacana provides IDE integration through a VS Code extension with a bundled Language Server Protocol (LSP) server. The extension supports .chcn files with syntax highlighting, real-time diagnostics, hover info, and go-to-definition.

VS Code

Installation (from source)

cd vscode-chacana
npm install
npm run build

Then press F5 in VS Code to launch an Extension Development Host, or install the built VSIX:

npx vsce package
code --install-extension vscode-chacana-0.1.0.vsix

Features

Syntax Highlighting

The extension provides immediate syntax coloring for .chcn files via a TextMate grammar. Tensors, indices, variance markers, operators, and functional operators are all highlighted.

Real-time Diagnostics

As you type, the LSP server provides two layers of diagnostics:

1. Syntax errors — via tree-sitter incremental parsing. Unclosed braces, invalid characters, and malformed expressions are flagged instantly.

2. Type checking — when the expression is syntactically valid, the full Chacana type checker runs:

   • Contraction consistency — contracted indices must have opposite variance and matching index type
   • Free index invariance — all terms in a sum must have identical free indices
   • Symmetry validity — symmetrized groups must have matching variance
   • Rank checking — tensor usage must match declared rank and pattern
   • Operator constraints — Hodge star needs a metric, Lie derivative needs a vector, etc.

Hover

Hover over a tensor name to see its declaration from the TOML context:

**R** — Tensor on manifold M
- Rank: 4
- Index pattern: [Contra, Covar, Covar, Covar]

Hover over a functional operator to see its documentation:

**Exterior derivative** d(omega) — maps a p-form to a (p+1)-form

Go-to-Definition

Ctrl+Click (or F12) on a tensor name jumps to its [tensor.X] declaration in the TOML context file.

Context Resolution

The LSP needs a TOML context file for rank checking and operator validation. It resolves the context in this order:

1. Directive — add a comment in the first 5 lines of your .chcn file:

   # context: path/to/context.toml
   R{^a _b _c _d}
   

2. Sibling file — the LSP walks up from the .chcn file's directory looking for chacana.toml.

Without a context, the LSP still provides syntax errors and structural checks (contraction, free index invariance).

Other Editors

The tree-sitter grammar (tree-sitter-chacana/) works natively in:

• Neovim — add tree-sitter-chacana to your tree-sitter config
• Helix — place the grammar in your runtime directory
• Zed — supports tree-sitter grammars directly

For these editors, copy the queries from tree-sitter-chacana/queries/:

• highlights.scm — syntax highlighting
• validation.scm — index extraction and variance consistency queries

Online Playground

Try the Playground to parse and type-check expressions in your browser — no installation needed.