gulpfile.js

'use strict';

const fs = require('fs');

const s3 = require('gulp-s3-upload')();
const log = require('lighthouse-logger');
const gulp = require('gulp');
const config = require('config');
const DateTime = require('luxon').DateTime;
const lighthouse = require('lighthouse');
const chromeLauncher = require('chrome-launcher');

 /**
 * Run lighthouse
 * @param {string} url - The url lighthouse is running against
 * @param {object} flags - Flags sent into Chrome
 * @param {object} config - Extra configuration
 */
function launchChromeAndRunLighthouse(url, flags, config = null) {
  return chromeLauncher.launch({chromeFlags: ['--disable-gpu', '--headless', '--no-sandbox']}).then(chrome => {
    flags.port = chrome.port;
    console.log(flags);
    return lighthouse(url, flags, config).then(results =>
      chrome.kill().then(() => results)
    );
  });
}

/**
 * Generate a report and save it to a file.
 * @param {object} site - This object holds the name, url and displayName
 * @param {string} type - The type of report we're generating json|html
 */
function generateReport(site, type) {
    return launchChromeAndRunLighthouse(site.url, {logLevel: 'info', output: type})
    .then((data) => {
      data = JSON.stringify(data);
      // timestamep will be used on the filename
      let timeStamp = DateTime.local().toISODate();

      // Directory may not exist yet
      if (!fs.existsSync(`reports/${site.name}`)) {
        fs.mkdirSync(`reports/${site.name}`);
      }

      // Directory may not exist yet
      if (!fs.existsSync(`reports/${site.name}/${type}`)) {
        fs.mkdirSync(`reports/${site.name}/${type}`);
      }

      fs.writeFileSync(`reports/${site.name}/${type}/${site.name}-${timeStamp}.${type}`, data);
    })
    .catch(handleError);
}

/**
 * Handle error
 */
const handleError = function(e) {
  console.error(e); // eslint-disable-line no-console
  throw e; // Throw to exit process with status 1.
};

// const flags = {logLevel: 'info', output: 'json'}; // available options - https://github.com/GoogleChrome/lighthouse/#cli-options
log.setLevel('info');


/**
* This is the entry point to Lighthouse, this will loop through our urls and run lighthouse against them
*/
gulp.task('lighthouse', function() {
  // The idea is to go through the list of sites and run lighthouse against them all
  let sites = config.get('pages');
  sites.forEach( async (v) => {
    // First lets get JSON
    // We don't want to overload the server by
    // await generateReport(v, 'json');
    await generateReport(v, 'html');
  })
});

gulp.task('default', ['lighthouse']);

Found this through the Lighthouse bug report. I'm curious if you'd share your finished solution for writing out the data from calling Lighthouse programmatically.