# @pi/lsp

LSP extension for pi coding agent. Provides LSP tools that the LLM can use to query language servers, plus automatic diagnostics after edit/write operations.

## Features

### LSP Tools (callable by LLM)

- `lsp_hover` - Get hover documentation for a symbol
- `lsp_definition` - Find the definition of a symbol
- `lsp_references` - Find all references to a symbol
- `lsp_completion` - Get completion suggestions
- `lsp_documentSymbol` - Get the symbol outline of a file
- `lsp_diagnostics` - Get lint/type-check diagnostics

### Auto-Check

Automatically runs LSP diagnostics after `edit` or `write` tool calls. If issues are found, sends a message with the diagnostics to the LLM.

**Enable/disable:**
```bash
pi --lsp-auto-check=false  # Disable auto-check
pi --lsp-auto-check=true   # Enable (default)
```

### Manual Check Command

Run diagnostics manually on specific files:
```bash
/lsp-check main.go utils.go
```

## Install

```bash
cd ~/.pi/extensions/lsp
npm install
```

## CLI Usage (for development/testing)

```
tsx ./cli.ts <file> <lsp_command> <req_data_json>
```

`req_data_json` is the raw LSP params for the command, minus
`textDocument.uri` (we inject that from `<file>`).

### Commands

- `hover`
- `definition`
- `references`
- `completion`
- `documentSymbol`
- `diagnostics` (waits briefly for the first `publishDiagnostics`)

### Examples

```bash
# Hover at line 224, col 23 (LSP is 0-indexed, so subtract 1)
npm run lsp -- backend/api/server.go hover \
  '{"position":{"line":223,"character":22}}'

# Go to definition
npm run lsp -- backend/api/server.go definition \
  '{"position":{"line":223,"character":22}}'

# Document symbols (no params needed)
npm run lsp -- backend/api/server.go documentSymbol '{}'

# Diagnostics
npm run lsp -- backend/api/server.go diagnostics '{}'
```

Set `LSP_DEBUG=1` to forward server stderr.

## Adding A Server

Edit `server.ts`:

```ts
{
  id: "rust-analyzer",
  match: ["rs"],
  command: "rust-analyzer",
  args: [],
  rootMarkers: ["Cargo.toml"],
  languageId: "rust",
}
```

## Adding A Command

1. Add to the `LspCommand` union in `src/types.ts`.
2. Add a handler in `src/commands.ts`.

## Future

- **Daemon with TTL** - `ServerConfig.idleTtlMs` is reserved for a future
  daemon that keeps language servers alive per `(server.id, rootUri)` to
  avoid cold-start latency. Not implemented; the CLI is short-lived and
  spawns fresh each invocation.