Feat/initial extension

[oddcelot]

Summary

Adds a Zed extension for UnoCSS, backed by the official @unocss/language-server — completion, hover, color previews, and matched-utility underlining.

This is split out of unocss/unocss#5227, which originally bundled the extension together with the server's new semanticTokens capability. The server-side change stays in the monorepo as this repo is the standalone extension that consumes it.

Why a new extension

There's an existing community extension (bajrangCoder/zed-unocss), but it relies on a fork of the language server and only attaches to TSX. This one uses the official server and additionally attaches to plain TypeScript and CSS, so Lit components (class="..." inside html`...` in .ts files) and stylesheets get completion, hover, and color previews too.

What's in here

• Rust/wasm extension (zed_extension_api) that fetches @unocss/language-server from npm on first use rather than vendoring it, with an offline fallback to an already-installed copy and a binary settings override for pointing at a local build.
• Settings forwarding — Zed lsp.unocss.settings are wrapped under the unocss namespace the server expects (unless already nested); initialization_options are forwarded too.
• Language mapping — maps Zed language names to the server's LSP languageIds, attaching to HTML, CSS, JavaScript, TypeScript, TSX, Vue, Svelte, Astro, Markdown, PHP, ERB (plus Elm/Marko/Pug, which only match when the user has those community language extensions installed).
• Docs — a README and an example .zed/settings.json covering setup, the Lit .ts/.js pipeline-filter requirement, and the opt-in underline configuration.

Underlining matched utilities

The server emits each matched utility as a unocss semantic token (an editor-agnostic equivalent of the VSCode underline decoration). As part of this work the server's semanticTokens default was switched from off to on, so tokens are emitted by default (set unocss.semanticTokens: false to opt out) — the earlier off-by-default behavior in unocss/unocss#5227 is superseded.

Rendering the tokens in Zed is still opt-in on the editor side: enable per-language semantic_tokens, then add a semantic_token_rules style under global_lsp_settings in user settings. The README documents both steps.

Notes for reviewers

• Not yet published to the Zed registry — the unocss ID there is currently the community extension, so publishing needs an ID takeover coordinated with the Zed maintainers. For now it installs as a dev extension.
• extension.toml authors/repository may want adjusting to the org's preference 🙂
• Testing is a bit hard, since it relies on the couterpart changes on the monorepo for the semantic tokens and you have to override the path to the LSP ( but doable)

Tip

The semantic tokens are quite nice and since this has to be configured in user settings anyway, you can adjust it to your heart's content.

[oddcelot]

Oh and btw: colors swatches work nicely too now (Zed apparetly only accepts RGB-esque color formats, so a bit of normalization was needed on the LSPs end)