Generate a theme from a Neovim colorscheme

You can generate a theme even when it is not in Lumis's bundled collection. This recipe uses shaunsingh/nord.nvim, whose source includes a GPL version 2 license. Generation does not add it to the bundled collection or change its source license. A bundled theme with the same name may come from a different plugin; use the generated file explicitly to select this source.

Prerequisites

Install the Lumis CLI, Git, and a Neovim version that provides the built-in vim.pack plugin manager. All three commands must be on PATH. Check Neovim before extracting:

nvim --headless --clean -c 'lua assert(vim.pack, "Neovim with vim.pack is required")' -c qa

The CLI starts a clean Neovim session in a temporary directory and installs the plugin there. It does not use your Neovim configuration or install the plugin into your normal Neovim data directory. Installation needs network access to the plugin repository. Only generate from repositories and setup code you trust: Neovim executes the plugin's Lua code.

Generate the JSON

lumis themes generate \
  --url https://github.com/shaunsingh/nord.nvim \
  --colorscheme nord \
  --appearance dark \
  --output nord.json

--colorscheme is the name Neovim loads, not necessarily the repository name. --appearance defaults to dark; use light for a light colorscheme. If the plugin needs configuration before it loads, pass Lua with --setup, for example --setup 'vim.g.nord_italic = false'. Without --output, JSON goes to stdout. See the command reference for all flags.

The JSON contains the theme's name, appearance, source revision, detected license, and highlight styles. Keep it with your application; generation is a build step, not something you need to run for each highlight.

Load the generated theme

Run these examples from the directory containing nord.json. Library callers load the file themselves and pass the resulting theme to a formatter; they do not look it up in the CLI's data directory.

import nord from './nord.json' with { type: 'json' };
import { highlight } from '@lumis-sh/lumis';
import { htmlInline } from '@lumis-sh/lumis/formatters';
import javascript from '@lumis-sh/wasm-javascript';

const html = await highlight(
  'const x = 1',
  htmlInline({ language: javascript, theme: nord }),
);

Keep the source license and notices

The license field records an SPDX expression detected from the plugin's license files. NONE means no license file was found; NOASSERTION means detection did not identify a known license. Neither is permission to redistribute. Check the upstream license and notices at the recorded revision, rather than relying only on automatic detection.

Extraction does not relicense a colorscheme under Lumis's license. Keep the source license, copyright notices, repository URL, and revision with the theme. The JSON's SPDX field is not a replacement for the full license text or notices; the generation command writes JSON, not a redistribution-ready license bundle.

Before distributing generated JSON, CSS, or a package containing them, review the source license's requirements for your intended use. For this GPL example, consider the applicable notice, license-copy, modification, corresponding-source, and copyleft obligations. Their application to an extracted theme and to a larger distribution depends on what is included and how it is distributed; generation alone does not settle those questions. If those obligations are unclear or do not fit your distribution, seek appropriate advice or choose a differently licensed source. The bundled theme reference lists each bundled theme's license.