feat(latex): add LaTeX language support

[NandishNaik01]

Add LaTeX Syntax Highlighting Support to Arborium

Overview

This PR introduces syntax highlighting support for LaTeX (.tex) files in Arborium.

The implementation uses the [latex-lsp/tree-sitter-latex](https://github.com/latex-lsp/tree-sitter-latex) grammar at commit 7e0ecdc02926c7b9b2e0c76003d4fe7b0944f957 (MIT licensed).

Classification

• Group: group-willow

  • Added alongside other markup/document languages such as Markdown, Typst, and AsciiDoc.

• Tier: 3

  • Classified as a niche document markup language.

• External Scanner: true

  • The grammar depends on an external scanner.c implementation.

---

Highlights Query Implementation

The upstream tree-sitter-latex grammar does not ship with a queries/ directory, so highlights.scm was implemented entirely from scratch.

The query covers the following constructs:

Commands

• command_name → @function

Environments

• \begin{...} → @function.builtin
• \end{...} → @function.macro

Math Regions

• displayed_equation
• inline_formula
• math_environment

All mapped to:

• @markup.raw

Sectioning

Supports:

• \section
• \subsection
• related heading commands

Mapped using:

• @namespace
• @markup.heading

Labels & References

• curly_group_label → @label

Citations

• curly_group_text_list → @string

File Inclusion

Covers:

• \usepackage
• \input
• related include/import commands

Mapped to:

• @keyword.storage.type
• @keyword.control.import

Text Formatting

• \textbf → @markup.bold
• \textit / \emph → @markup.italic

Additional Coverage

• Comments → @comment
• Punctuation
• Operators

---

Grammar Compatibility Notes

Field names were verified directly against the grammar’s node-types.json.

Some references from Helix queries required updates due to renamed fields in the upstream grammar:

• curly_group_text → curly_group_label
• path: → paths: in bibtex_include

---

Demo & Verification

Tested locally using:

cargo xtask build --dev latex
cargo xtask serve --dev

Highlighting renders correctly across multiple themes, including:

• Tokyo Night
• Catppuccin Latte
• other bundled themes

The following syntax categories were visually verified:

• commands
• environments
• math regions
• sections/headings
• comments
• inline formatting

---

Tests

running 2 tests
test tests::test_corpus ... ok
test tests::test_grammar ... ok

test result: ok. 2 passed; 0 failed; 0 ignored

---

Files Added

langs/group-willow/latex/def/
├── arborium.yaml          # language definition
├── grammar/
│   ├── grammar.js         # from tree-sitter-latex
│   └── scanner.c          # from tree-sitter-latex src/scanner.c
├── queries/
│   └── highlights.scm     # custom highlights query
└── samples/
    └── sample.tex         # representative LaTeX sample

demo/samples/latex.tex     # live demo sample

[NandishNaik01]

Optional follow-up: indents.scm

LaTeX has a natural indentation boundary with \begin{env} / \end{env} — happy to add an indents.scm in a follow-up PR if that would be useful. No other group-willow language currently ships one, so I left it out of this PR to keep the scope minimal, but can add it if the maintainers want it.

Example of what it would look like:

(begin_command) @indent
(end_command) @outdent

Let me know!

[NandishNaik01]

Update: is now included in this PR — indents and outdents using the correct (begin) @indent.begin / (end) @indent.end capture names per arborium convention. First group-willow language to ship one.