rust-analyzer/editors/code/src/config.ts

import * as vscode from 'vscode';

import { Server } from './server';

export class Config {
    public highlightingOn = true;

    constructor() {
        vscode.workspace.onDidChangeConfiguration(_ =>
            this.userConfigChanged()
        );
        this.userConfigChanged();
    }

    public userConfigChanged() {
        const config = vscode.workspace.getConfiguration('ra-lsp');
        if (config.has('highlightingOn')) {
            this.highlightingOn = config.get('highlightingOn') as boolean;
        }

        if (!this.highlightingOn && Server) {
            Server.highlighter.removeHighlights();
        }
    }
}