deno/cli/lsp

Deno Language Server

The Deno Language Server provides a server implementation of the Language Server Protocol which is specifically tailored to provide a Deno view of code. It is integrated into the command line and can be started via the lsp sub-command.

⚠️ The Language Server is highly experimental and far from feature complete. This document gives an overview of the structure of the language server.

Structure

When the language server is started, a LanguageServer instance is created which holds all of the state of the language server. It also defines all of the methods that the client calls via the Language Server RPC protocol.

Custom requests

The LSP currently supports the following custom requests. A client should implement these in order to have a fully functioning client that integrates well with Deno:

• deno/cache - This command will instruct Deno to attempt to cache a module and all of its dependencies. If a referrer only is passed, then all dependencies for the module specifier will be loaded. If there are values in the uris, then only those uris will be cached.

  It expects parameters of:

  interface CacheParams {
    referrer: TextDocumentIdentifier;
    uris: TextDocumentIdentifier[];
  }
  

• deno/performance - Requests the return of the timing averages for the internal instrumentation of Deno.

  It does not expect any parameters.

• deno/reloadImportRegistries - Reloads any cached responses from import registries.

  It does not expect any parameters.

• deno/virtualTextDocument - Requests a virtual text document from the LSP, which is a read only document that can be displayed in the client. This allows clients to access documents in the Deno cache, like remote modules and TypeScript library files built into Deno. The Deno language server will encode all internal files under the custom schema deno:, so clients should route all requests for the deno: schema back to the deno/virtualTextDocument API.

  It also supports a special URL of deno:/status.md which provides a markdown formatted text document that contains details about the status of the LSP for display to a user.

  It expects parameters of:

  interface VirtualTextDocumentParams {
    textDocument: TextDocumentIdentifier;
  }
  

Settings

There are several settings that the language server supports for a workspace:

• deno.enable
• deno.config
• deno.import_map
• deno.code_lens.implementations
• deno.code_lens.references
• deno.code_lens.references_all_functions
• deno.suggest.complete_function_calls
• deno.suggest.names
• deno.suggest.paths
• deno.suggest.auto_imports
• deno.imports.hosts
• deno.lint
• deno.unstable

There are settings that are support on a per resource basis by the language server:

• deno.enable

There are several points in the process where Deno analyzes these settings. First, when the initialize request from the client, the initializationOptions will be assumed to be an object that represents the deno namespace of options. For example, the following value:

{
  "enable": true,
  "unstable": true
}

Would enable Deno with the unstable APIs for this instance of the language server.

When the language server receives a workspace/didChangeConfiguration notification, it will assess if the client has indicated if it has a workspaceConfiguration capability. If it does, it will send a workspace/configuration request which will include a request for the workspace configuration as well as the configuration of all URIs that the language server is currently tracking.

If the client has the workspaceConfiguration capability, the language server will send a configuration request for the URI when it received the textDocument/didOpen notification in order to get the resources specific settings.

If the client does not have the workspaceConfiguration capability, the language server will assume the workspace setting applies to all resources.