dsh-tool-lsp

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An LSP tool surface for DeepSeek Harness: real language-server diagnostics, formatting, rename, code actions and symbol navigation, exposed as five tools the model can call directly.

Tools

Tool	What it does	Writes to disk
lsp_diagnostics	File diagnostics, merging the pull and push channels	no
lsp_format	Whole-file or range formatting	yes
lsp_rename	Semantic rename, across files when the server says so	yes
lsp_code_action	Fixes the language server is willing to apply	yes (when an action is applied)
lsp_symbols	Document outline / workspace symbol search	no

Writes go through the Harness filesystem observation policy: a file changed by someone else since this call read it fails with LSP_WRITE_CONFLICT rather than being silently overwritten.

Install

dsh plugin --profile web add dsh-tool-lsp

Enable it from dshmarket. The plugin is off by default — click the switch when you want it, and it takes effect immediately with no restart. The enabled state does not survive a restart.

Configuration

The language-server table lives in the user profile's patch layer ($DSH_HOME/profiles/<name>/cordis.patch.yml), never in the plugin package: the package's own cordis.patch.yml has to stay plain insert rows, or dshmarket cannot hot-mount or hot-unmount this plugin.

- id: lsp
  config:
    servers:
      vtsls:
        command: vtsls
        args: ["--stdio"]
        extensionToLanguage:
          ".ts": typescript
          ".tsx": typescriptreact
          ".js": javascript
          ".jsx": javascriptreact
        projectMarkers: ["package.json", "tsconfig.json"]
        configuration:                 # the answer to workspace/configuration
          typescript:
            preferences:
              includePackageJsonAutoImports: "on"

      rust:
        command: rust-analyzer
        extensionToLanguage:
          ".rs": rust
        projectMarkers: ["Cargo.toml"]

      biome:
        command: biome
        args: ["lsp-proxy"]
        extensionToLanguage:
          ".json": json
          ".css": css
        projectMarkers: ["biome.json"]

# The switch needs its own row: same-id rows merge key by key, and folding them
# into one row breaks the market's toggle
- id: lsp
  disabled: true

Server entry fields

Field	Required	Default	Meaning
command	✅	—	Executable name, resolved on PATH at mount; a typo fails there, not on first call
extensionToLanguage	✅	—	Extension → LSP language id
fileGlobs		[]	Path globs, highest routing priority
projectMarkers		[]	Project file names, used to split one extension across servers
args		[]	Launch arguments
env		{}	Extra environment entries
initializationOptions		null	initializationOptions sent with initialize
configuration		null	Answer to workspace/configuration, resolved per requested section
formattingOptions		null	Overrides the global formatting options (tabSize / insertSpaces)

Routing

Matched in order, first hit wins:

1. fileGlobs
2. projectMarkers — the marker file in the file's nearest ancestor; only chooses among entries that already map the extension
3. extensionToLanguage — first match in configuration order

Top-level options

maxDiagnostics (200), maxSymbols (100), maxCodeActions (50), maxResultChars (16000), maxDiffLines (60), maxDocumentBytes (8 MiB), timeoutMs (60000).

Positions

Tool arguments take 1-based UTF-16 line / character, matching editors. The 0-based wire form and the utf-8 / utf-32 encodings some servers negotiate are converted internally — the model never has to think about it.

Requirements

The language servers themselves must be on PATH; this plugin does not install them. vtsls, biome, rust-analyzer, ty, ruff, or any other LSP server.

Known limitations

• biome and ruff do not implement textDocument/documentSymbol, so lsp_symbols returns LSP_UNSUPPORTED for them. They serve diagnostics and formatting only.
• A cold server (rust-analyzer is the usual example) may answer a first diagnostic pull with nothing at all while it indexes. The plugin retries with backoff and, once out of attempts, reports what it has.

Development

npm test                 # 121 unit tests, including protocol coverage over a fake server
npm run verify:servers   # every server configured in the patch layer, over real requests

verify:servers reads the servers: table out of the profile patch, starts each real server, and issues one request per advertised capability. Usage: node test/verify-servers.mjs [profileDir].

Restart the process after changing plugin source. The market switch changes whether the plugin is mounted, immediately — but it does not load new code from disk into a running process (ESM module cache, confirmed by measurement).

License

MIT