Expose page functions to custom gatherers

Provide the steps to reproduce

1. Run LH on https://bristololdvic.org.uk with my massive wrapper function and custom gatherer/audit library…

What is the current behavior?

Got a custom audit to test for http status code- snippet below.

const mainResource = await artifacts.requestMainResource({URL: artifacts.URL, devtoolsLog});
 const statusCode = mainResource.statusCode;

 if (statusCode >= 500 && statusCode < 600) {
   return {
     rawValue: false,
     displayValue: `Page returned HTTP status code of ${statusCode}`,
   };
 }

 return {
   rawValue: true,
   displayValue: `Page returned HTTP status code of ${statusCode}`,
 };

What happens is artifacts.requestMainResource({URL: artifacts.URL, devtoolsLog}) rejects with TypeError: devtoolsLog.forEach is not a function

This is nothing to do with the arguments I pass in to the method; I have a feeling the issue is with https://github.com/GoogleChrome/lighthouse/blob/1098f952d5c75b22668aa572532415f81d2817af/lighthouse-core/lib/network-recorder.js#L355

The rejection of this promise then exits this function prematurely, and rawValue will be null which isn’t handy for further use!

What is the expected behavior?

Expected behaviour is artifacts.requestMainResource({URL: artifacts.URL, devtoolsLog}) to resolve, returning the main resource so it’s parameters can be used for tests in audits.

Environment Information

• Affected Channels:
• Lighthouse version: lighthouse@2.9.4
• Node.js version: v10.14.1
• Operating System: Windows 10 Home

[patrickhulce]

@upugo-dev should be AFAIK

[upugo-dev]

we decided not to do this for now.

We can encourage folks to head to page-functions.js and copy/paste out of it, but fundamentally these are just regular functions to be run in a web page. There’s no Lighthouse magic sauce it would be helpful for folks to have access to, so let’s not commit to it as part of our API.

That makes a lot of sense, thanks for following up.