CSS Variable Language Server

A Language Server Protocol (LSP) implementation focused on CSS custom properties (variables). It indexes variables across your workspace and provides completions, hover resolution, and diagnostics.

Features

• Context-aware completion after var( in CSS files, HTML <style> blocks/style="" attributes, and JS/TS string literals, with relevance scoring.
• Workspace-wide indexing across .css, .scss, .sass, .less, plus HTML <style> blocks and inline styles.
• Cascade-aware hover that orders definitions by !important, specificity, and source order.
• Go to definition, find references, and rename support.
• Diagnostics for undefined variables used via var(--name).
• Color decorations and a color picker with hex/rgb/hsl presentations, including named colors in custom property values and resolved var(--...) usages.

Getting Started

Prerequisites

• Node.js (ES2020-compatible; v16+ recommended)
• npm

Install / Build

npm install
npm run compile

Run

# via local build
node out/server.js --stdio

# or, if installed from npm
css-variable-lsp --stdio

Editor Integration

This is a standalone LSP server. Configure it in any LSP client.

VS Code extension

Zed extension

Configuration

Command-line flags:

• --no-color-preview
• --color-only-variables (show colors only on var(--...) usages)
• --lookup-files "<glob>,<glob>" (comma-separated list of glob patterns)
• --lookup-file "<glob>" (repeatable)
• --ignore-globs "<glob>,<glob>" (comma-separated list of glob patterns)
• --ignore-glob "<glob>" (repeatable)
• --path-display=relative|absolute|abbreviated
• --path-display-length=N (only used for abbreviated; 0 disables shortening)
• --undefined-var-fallback=warning|info|off (controls diagnostics for undefined vars when a var() fallback exists)

Environment variables:

• CSS_LSP_COLOR_ONLY_VARIABLES=1 (same as --color-only-variables)
• CSS_LSP_LOOKUP_FILES (comma-separated glob patterns; ignored if CLI lookup flags are provided)
• CSS_LSP_IGNORE_GLOBS (comma-separated glob patterns; ignored if CLI ignore flags are provided)
• CSS_LSP_DEBUG=1 (enable debug logging)
• CSS_LSP_PATH_DISPLAY=relative|absolute|abbreviated
• CSS_LSP_PATH_DISPLAY_LENGTH=1 (same as --path-display-length)
• CSS_LSP_UNDEFINED_VAR_FALLBACK=warning|info|off

Defaults:

• --path-display: relative
• --path-display-length: 1
• --undefined-var-fallback: warning
• Lookup globs:
  • **/*.css
  • **/*.scss
  • **/*.sass
  • **/*.less
  • **/*.html
  • **/*.vue
  • **/*.svelte
  • **/*.astro
  • **/*.ripple
• Ignore globs:
  • **/node_modules/**
  • **/dist/**
  • **/out/**
  • **/.git/**

abbreviated mode shortens each directory segment (except the final one) to the configured length, matching fish-style prompt shortening. Lookup/ignore globs accept standard glob patterns (including brace expansions like **/*.{css,scss}). Ignore globs replace the defaults when provided (include any defaults you still want to keep).

Completion Path Examples

Assume a variable is defined in /Users/you/project/src/styles/theme.css and your workspace root is /Users/you/project.

• --path-display=relative (default):
  • Defined in src/styles/theme.css
• --path-display=absolute:
  • Defined in /Users/you/project/src/styles/theme.css
• --path-display=abbreviated --path-display-length=1:
  • Defined in s/s/theme.css
• --path-display=abbreviated --path-display-length=2:
  • Defined in sr/st/theme.css
• --path-display=abbreviated --path-display-length=0 (no shortening):
  • Defined in src/styles/theme.css

Cascade Awareness (Best-Effort)

Hover and color resolution use CSS cascade rules (specificity, !important, source order) but do not model DOM nesting or selector combinators. See LIMITATIONS.md for details.

Project Structure

• src/ TypeScript source
• out/ compiled server (npm bin entry)
• LIMITATIONS.md known limitations

Testing

npm test