# Lemma LSP
Language Server Protocol implementation for [Lemma](https://github.com/lemma/lemma). Provides inline diagnostics and editor features for `.lemma` files.
## Features
- **Diagnostics** — Parse and planning (semantic) errors are published as you type. Parse errors are shown immediately; a debounced (250ms) full workspace validation adds planning errors. Errors use source spans where available; diagnostics are cleared when a file is closed.
- **Workspace validation** — On native, when the client provides a workspace root, the server scans for `.lemma` files under that root at startup (skips hidden directories only) and runs full planning so cross-spec errors (missing spec/type refs, circular dependencies, etc.) are reported per file. The client keeps the server in sync via file open/change/close. On WASM, only the open file is validated (no filesystem).
- **Registry links** — `@`-prefixed Registry references (e.g. `spec @user/workspace/somespec`, `type ... from @iso/countries/alpha2`) are turned into clickable links when the Registry (LemmaBase) provides a URL. Works even when the file has parse errors (text-based scan).
- **Registry hover** — Hovering on a registry `uses` reference (qualifier or spec name) shows a popup with exactly two navigation entries: a hover-markdown link to the LemmaBase page for the repository, and the `DocumentLink` Ctrl+Click hint to the locally fetched bundle under `<workspace>/lemma_deps/<qualifier>.lemma` at the resolved `spec ...` line.
- **Embedded stdlib navigation** — `uses lemma units` (and any other reserved `repo lemma` import) becomes a clickable link to a view-only snapshot at `<workspace>/lemma_deps/lemma.std`. The file is written lazily the first time `document_link` runs on a spec that imports it, and is excluded from every `.lemma` discovery pass because of its `.std` extension. The repository qualifier link opens the file; the spec name link opens it at the `spec ...` line. The VS Code extension registers the `lemma.std` filename so the snapshot still gets full Lemma syntax highlighting.
- **Text document sync** — Full file sync on open, change, and close; no incremental sync.
The server uses the Lemma engine with **registry** support (LemmaBase) for resolving `@...` identifiers and communicates over stdio (native) or browser streams (WASM).
## Build
From the **repository root**:
```bash
cargo build --release -p lemma
```
The LSP runs as `lemma lsp` (stdio).
The crate also supports a **WASM** build for in-browser use; the library entry point is `lsp::browser::serve`. The Lemma WASM playground does not use the LSP for diagnostics; it uses the engine’s `getDiagnostics` API directly for inline errors.
## Usage
Run the server over stdio:
```bash
lemma lsp
```
- **VS Code / Cursor** — Use the extension under [editors/vscode](editors/vscode). It runs `lemma lsp` automatically and looks for `target/release/lemma` when the workspace root is the Lemma repo, or uses the `lemma.lspServerPath` setting. Format-on-save and diagnostics only work when the LSP is running; see [editors/vscode/README.md](editors/vscode/README.md) if format on save does nothing.
- **Other editors** — Point your editor’s LSP client at `lemma` with argument `lsp` and stdio transport.
## Layout
- **`src/`** — LSP server (tower-lsp): server, diagnostics, registry links, workspace model, registry integration.
- **`editors/`** — Editor-specific clients and config (e.g. VS Code extension); see [editors/README.md](editors/README.md).