Logging doesn't work in programmatic use code example

[staceytay]

Logging doesn't output expected log level logs in the example

const fs = require('fs');
const lighthouse = require('lighthouse');
const chromeLauncher = require('chrome-launcher');
const log = require('lighthouse-logger');

(async () => {
  log.setLevel('info');
  const chrome = await chromeLauncher.launch({chromeFlags: ['--headless']});
  const options = {output: 'html', onlyCategories: ['performance'], port: chrome.port};
  const runnerResult = await lighthouse('https://example.com', options);

  // `.report` is the HTML report as a string
  const reportHtml = runnerResult.report;
  fs.writeFileSync('lhreport.html', reportHtml);

  // `.lhr` is the Lighthouse Result as a JS object
  console.log('Report is done for', runnerResult.lhr.finalUrl);
  console.log('Performance score was', runnerResult.lhr.categories.performance.score * 100);

  await chrome.kill();
})();

from https://github.com/GoogleChrome/lighthouse/blob/master/docs/readme.md#using-programmatically.

Provide the steps to reproduce

1. Run the code above using the lighthouse CLI.

What is the current behavior?

Output from running the sample code above:

Report is done for https://example.com/
Performance score was 100

What is the expected behavior?

  status Connecting to browser +0ms
  status Resetting state with about:blank +25ms
  status Benchmarking machine +104ms
  status Initializing… +504ms
  /* ...truncated... */
  status Auditing: Uses passive listeners to improve scrolling performance +13ms
  status Generating results... +0ms
Report is done for https://example.com/
Performance score was 100

Environment Information

• Affected Channels: CLI
• Lighthouse version: 6.1.1
• Chrome version: NA
• Node.js version: v12.16.3
• Operating System: macOS

Related issues
#10788

Proposed Changes

1. Update the example code snippet above to pass in the logLevel for Flags and remove the use of lighthouse-logger.

onst chromeLauncher = require('chrome-launcher');
-const log = require('lighthouse-logger');
 
 (async () => {
-  log.setLevel('info');
   const chrome = await chromeLauncher.launch({chromeFlags: ['--headless']});
-  const options = {output: 'html', onlyCategories: ['performance'], port: chrome.port};
+  const options = {logLevel: 'info', output: 'html', onlyCategories: ['performance'], port: chrome.port};
   const runnerResult = await lighthouse('https://example.com', options);

2. Update the Turn on logging section in the same doc.

-If you want to see log output as Lighthouse runs, include the `lighthouse-logger` module
-and set an appropriate logging level in your code. You'll also need to pass
+If you want to see log output as Lighthouse runs, set an appropriate logging level in your code and pass
 the `logLevel` flag when calling `lighthouse`.
 
 ```javascript
-const log = require('lighthouse-logger');
-
 const flags = {logLevel: 'info'};
-log.setLevel(flags.logLevel);
 
 launchChromeAndRunLighthouse('https://example.com', flags).then(...);

If the proposed changes above are ok, I'd be happy to submit a PR to fix them :)

[patrickhulce]

Thanks @staceytay those changes would be very welcome in a PR! :)

[staceytay]

Closing since fixed in #11116