Highlight source code to HTML or Clojure/EDN Hiccup using Helix’s tree-sitter grammars and queries.

It reads the precompiled grammars and highlights.scm / injections.scm / locals.scm queries from a Helix runtime, so it covers whatever languages that runtime provides. Grammar loading, query inherits resolution, injections, and locals are handled by tree-house, the same library Helix uses.

cargo build --release

The binary is target/release/dathan.

dathan [OPTIONS] [FILE]

If FILE is omitted, source is read from stdin. With stdin there is no filename to detect from, so pass --lang (or rely on a #! shebang line).

Options:

--format <html|edn-hiccup>   Output format. Default: edn-hiccup.
--lang <name>                Force a language instead of detecting it.
--runtime <path>             Extra runtime root, highest priority. Repeatable.
--languages <path>           Base languages.toml. The user config is still merged on top.
--theme <path>               theme.toml for --emit-css.
--emit-css                   Write a CSS stylesheet from the theme and exit. Ignores FILE.
-o, --output <path>          Output file. Default: stdout.

Examples:

dathan src/main.rs
dathan --format html src/main.rs -o main.html
cat src/main.rs | dathan --lang rust
dathan --emit-css --theme ~/source/helix/theme.toml -o theme.css

Runtime roots are searched in this order, first match wins:

1. --runtime paths
2. $HELIX_RUNTIME
3. ~/.config/helix/runtime

The language registry is read from ~/source/helix/languages.toml (or --languages), with ~/.config/helix/languages.toml merged over it by language name.

Language detection uses the file extension, then file-types globs, then a #! shebang line. Override with --lang.

Both formats name spans by scope. A dotted scope becomes space-separated hierarchical classes, so keyword.control.conditional is rendered as keyword keyword-control keyword-control-conditional.

HTML:

<div class="dathan">
  <pre><code><span class="keyword keyword-function">fn</span> …</code></pre>
</div>

EDN Hiccup:

[:div.dathan [:pre [:code [:span {:class "keyword keyword-function"} "fn"] " " …]]]

CSS from --emit-css targets the most specific class, for example .keyword-control { color: …; }. Palette names in the theme are resolved.

cargo test

Copyright © 2026 Tom Waddington

Distributed under the MIT License. See LICENSE file for details.