Heavily documented sample code for https://code.visualstudio.com/api/language-extensions/language-server-extension-guide

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

• 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 start compiling the client and server in watch mode.
• Switch to the Run and Debug View in the Sidebar (Ctrl+Shift+D).
• Select Launch Client from the drop down (if it is not already).
• Press ▷ to run the launch config (F5).
• 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.