CLI, Node: Performance Score null if running headless

[adrian-cerdeira]

Provide the steps to reproduce

1. Run Lighthouse CLI on URL https://www.viag.ch
2. Use parameters --chrome-flags="--headless"

What is the current behavior?

If parameter headless is used, the performance score is zero. This leads to an error with LCP.

But if headless parameter is not used, then the LCP error get ignored and the score is between 0.9 -1.

What is the expected behavior?

Performance score should be between 0 to 1.

Environment Information

• Affected Channels: CLI, Node
• Lighthouse version: 6.1.1
• Chrome version: 83.0.4103.116
• Node.js version: 12.16.1
• Operating System: Windows

[patrickhulce]

Thanks for filing @adrian-cerdeira! I'm not able to reproduce this with your specified environment settings though.

This is what I get

Are you 100% sure it's using Chrome 83? This is the sort of error message you would get if it were using an older Chromium version.

[adrian-cerdeira]

Here the proof:

Also here is the command I have executed, maybe I am doing something wrong:
lighthouse https://www.viag.ch --chrome-flags="--headless"

[patrickhulce]

That's the correct command 👍 I'm not sure what's going on, and I don't know how we can help if we can't reproduce it :/

Is it possible this page serves different content to your geo and my geo? (I'm based in the central US)

[adrian-cerdeira]

It could be. My geo is based from switzerland.

[aseem-upadhyay]

in my case. if i run the test in a dockerised environment, it works fine when checking for desktop but returns a score of null when executing for mobile.

However, the same command if i run from my terminal, works fine for both desktop and mobile.

Not sure what's causing this

Environment Information
Lighthouse version: 7.0.1
Node version: 12.20.1

[wafendy]

I'm also getting performance is null most of the time. The error message I'm getting is:

Chrome didn't collect any screenshots during the page load. 
Please make sure there is content visible on the page, and 
then try re-running Lighthouse. (NO_SCREENSHOTS)

For detailed docker setup can see this post:
https://stackoverflow.com/questions/66251473/chrome-aws-lambda-lighthouse-always-results-in-error-connect-econnrefused-127/66256129#66256129

[paulirish]

I would also suggest folk running into this try --headless=chrome which is a new (mode) for headless which has much more headful behavior while still being headless. :)