CSS Variable LSP (Rust Implementation)

A Language Server Protocol implementation for CSS Variables, written in Rust.

Status: Complete

This is a ground-up Rust rewrite of the TypeScript/Node-based css-variable-lsp, eliminating the Node/npm dependency for the Zed extension.

Features

CSS parsing for variable definitions and var() usage tracking
HTML parsing for <style> blocks and inline styles (custom DOM scanner)
Cascade sorting and specificity calculation
LSP features: completion, hover, definition, references, rename, diagnostics, document/workspace symbols
Workspace scanning and color provider (hex/rgb/hsl + named colors)

Autocomplete Contexts

TypeScript LSP (css-variable-lsp):

Triggers on -, (, and :.
Returns items only in CSS value contexts (after a : and before the next ;).
CSS-like files: inside rules/declarations (requires {} context).
HTML-like files: inside style="..." attributes or <style>...</style> blocks.
JS/TS/JSX/TSX: only inside string literals or template literal text (not inside ${...}).
Insert text: --name if already inside var(, otherwise var(--name).

Rust LSP (this repo):

Matches the TypeScript LSP behavior above.
Document kind detection uses language ID when available, otherwise extensions derived from lookupFiles.

Building

cargo build --release

Release Assets (Local)

Build and package release assets into dist/ (tar.gz on Unix, zip on Windows):

./scripts/build-release-assets.sh

To build a subset of targets:

./scripts/build-release-assets.sh x86_64-apple-darwin aarch64-apple-darwin

Running

cargo run --release

The LSP server communicates via stdin/stdout using the Language Server Protocol.

Architecture

main.rs - Entry point, sets up async runtime and LSP server
lsp_server.rs - LSP protocol handlers (implements tower_lsp_server::LanguageServer)
manager.rs - CSS variable manager (stores definitions/usages, DOM trees)
types.rs - Core data types (CssVariable, CssVariableUsage, Config, etc.)
parsers/ - CSS and HTML parsing (definitions + var() usages)
dom_tree.rs - Lightweight HTML scanner for selector matching
specificity.rs - Specificity calculation and cascade ordering
workspace.rs - Workspace scanning and file discovery
flags.rs - Reusable flag parsing helper functions
runtime_config.rs - CLI/env configuration parsing
path_display.rs - Path formatting for hover/completion
color.rs - Color parsing and color provider helpers

Configuration

The LSP server accepts configuration via CLI flags and environment variables.

Feature Flags

Flag	CLI (disable)	Env var	Default	Description
Color preview	`--no-color-preview`	`CSS_LSP_COLOR_PREVIEW=0`	true	Enable color picker
Color only variables	`--color-only-variables`	`CSS_LSP_COLOR_ONLY_VARIABLES=1`	false	Colors only on var()
Lookup files	`--lookup-files`	`CSS_LSP_LOOKUP_FILES`	None	File extensions to scan
Ignore globs	`--ignore-globs`	`CSS_LSP_IGNORE_GLOBS`	None	Patterns to exclude
Path display	`--path-display`	`CSS_LSP_PATH_DISPLAY`	relative	Path format mode
Path length	`--path-display-length`	`CSS_LSP_PATH_DISPLAY_LENGTH`	1	Abbreviation length
Undefined fallback	`--undefined-var-fallback`	`CSS_LSP_UNDEFINED_VAR_FALLBACK`	warning	Fallback diagnostic level
Suggest add fallback	`--no-suggest-add-fallback`	`CSS_LSP_SUGGEST_ADD_FALLBACK=0`	true	Add fallback quickfix
Suggest color vars	`--no-suggest-exact-color-variables`	`CSS_LSP_SUGGEST_EXACT_COLOR_VARIABLES=0`	true	Color replacement suggestions

Examples

# Disable color preview
./css-variable-lsp --no-color-preview

# Set lookup files via env
CSS_LSP_LOOKUP_FILES="*.css,*.scss" ./css-variable-lsp

# Combine options
./css-variable-lsp --path-display=abbreviated:2 --no-suggest-add-fallback

Dependencies

tower-lsp-server - LSP server framework
tokio - Async runtime
globset / walkdir - Workspace scanning
csscolorparser - Color value parsing
regex / pathdiff - Parsing helpers and path formatting

License

GPL-3.0

css-variable-lsp 0.2.2