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Elixir

When you want explicit error handling​

Use highlight/2 when invalid user input, formatter options, or language detection should stay in the normal control flow.

case Lumis.highlight(source, formatter: {:html_inline, language: "elixir"}) do

  {:ok, html} -> html

  {:error, reason} -> handle_error(reason)

end

highlight/2 returns {:ok, output} or {:error, reason}.

When you want the highlighted output directly​

Use highlight!/2 when failures should raise immediately, such as in scripts, trusted internal code, or examples.

html = Lumis.highlight!(source, formatter: {:html_inline, language: "elixir"})

highlight!/2 returns the highlighted output or raises.

Language selection​

Elixir accepts several forms:

Lumis.highlight!(code, formatter: {:html_inline, language: "elixir"})

Lumis.highlight!(code, formatter: {:html_inline, language: ".ex"})

Lumis.highlight!(code, formatter: {:html_inline, language: "lib/my_app.ex"})

Lumis.highlight!(code)

Omitting language from the formatter enables auto-detection.

Parser loading​

Lumis loads missing root and injected languages automatically. Parser WASM is pinned to an exact package version, size, and SHA-256 digest, then cached in the platform user cache directory.

:ok = Lumis.preload_languages(["elixir", "html", "javascript", "css"])

Preload expected languages during application startup when request latency matters. Set LUMIS_WASM_CACHE_DIR to override the cache location and LUMIS_WASM_OFFLINE=1 to reject uncached parsers.

A custom :wasm_resolver application setting can return {:ok, bytes}, {:file, path}, or a URL:

config :lumis, :wasm_resolver, fn parser ->

  {:file, Path.join("/app/wasm", "#{parser.wasm_name}.wasm")}

end

Discover supported languages and themes​

Lumis.available_languages()

Lumis.available_themes()

Lumis.Theme.get("github_light")

See Lumis and Lumis.Theme on HexDocs.

Phoenix and LiveView​

Highlighted HTML must be rendered as raw HTML in templates.

code = Lumis.highlight!(source, formatter: {:html_inline, language: "elixir"})

{Phoenix.HTML.raw(@code)}

For linked CSS output, also mount a theme stylesheet through Plug.Static as shown in CSS Theme Files.

Light/dark mode​

See Light/Dark Mode for three approaches to theme switching (CSS light-dark(), media queries, and manual toggle).

Custom themes​

{:ok, theme} = Lumis.Theme.from_file("/path/to/theme.json")

{:ok, theme} = Lumis.Theme.from_json(theme_json)

Then pass the resulting theme struct into the formatter options.

Validation​

# validate options before passing to highlight

Lumis.validate_options!(formatter: {:html_inline, language: "elixir", theme: "dracula"})



# inspect defaults

Lumis.default_options()

Use validate_options!/1 when your app exposes formatter options to users (e.g., config files, admin panels). It raises on invalid values.