This is a small coc-nvim plugin to wrap the Java language server in a Lombok agent to allow completion for Lombok models. Place this file in `.config/nvim/coc-extensions/` with a copy of lombok.jar as well.

lombok.js

const { commands, workspace, ConfigurationTarget, extensions} = require('coc.nvim')

exports.activate = async function(context) {
    await setLombokToVSCode(context);
}

async function setLombokToVSCode(context) {
let lombokConfig  = {
        "path": "lombok.jar",
        "vmArgsKey": "java.jdt.ls.vmargs",
        "vmArgsValue": `-javaagent:${context.extensionPath + '/lombok.jar'}`
    }

    const previousVmArguments = getSetting(lombokConfig.vmArgsKey);

    if (!previousVmArguments) {
        return updateVMSettings(lombokConfig.vmArgsKey, lombokConfig.vmArgsValue);
    } else if (!previousVmArguments.includes(lombokConfig.path)) {
        return updateVMSettings(lombokConfig.vmArgsKey, previousVmArguments.trim() + ' ' + lombokConfig.vmArgsValue);
    } else if (!previousVmArguments.includes(lombokConfig.vmArgsValue)) {
        return updateVMSettings(lombokConfig.vmArgsKey, previousVmArguments.split('-javaagent:')[0].trim() + ' ' + lombokConfig.vmArgsValue);
    }

    return true;
}

async function updateVMSettings(key, value) {
    await workspace.getConfiguration().update(key, value, ConfigurationTarget.Global);

    const newVmArguments = getSetting(key);

    return newVmArguments !== undefined && newVmArguments === value;
}

function getSetting(key) {
    return workspace.getConfiguration().get(key);
}