LSP Example

Heavily documented sample code for


This Language Server works for plain text file. It has the following language features:

  • Completions
  • Diagnostics regenerated on each file change or configuration change

It also includes an End-to-End test.


├── client // Language Client
│   ├── src
│   │   ├── test // End to End tests for Language Client / Server
│   │   └── extension.ts // Language Client entry point
├── package.json // The extension manifest.
└── server // Language Server
    └── src
        └── server.ts // Language Server entry point

Compile and Run

  • Run npm install in this folder. This installs all necessary npm modules in both the client and server folder
  • Open VS Code on this folder.
  • Press Ctrl+Shift+B to compile the client and server.
  • Switch to the Debug viewlet.
  • Select Launch Client from the drop down.
  • Run the lauch config.
  • If you want to debug the server as well use the launch configuration Attach to Server
  • In the [Extension Development Host] instance of VSCode, open a document in 'plain text' language mode.
    • Type j or t to see Javascript and TypeScript completion.
    • Enter text content such as AAA aaa BBB. The extension will emit diagnostics for all words in all-uppercase.