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Check for invisible text during webfont load is passing when it should be failing #6698

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amclin opened this Issue Dec 1, 2018 · 5 comments

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@amclin

amclin commented Dec 1, 2018

I was investigating workarounds to google/fonts#358 when I discovered that Lighthouse is incorrectly marking a passing state for the "invisible text while web fonts are loading" check. If there is an font-display declaration, LH passes the check, even when that declaration is non functional and there is still invisible text.

Provide the steps to reproduce

  1. Turn on LH throttling
  2. Run LH Performance audit on https://festive-snout.glitch.me/
  3. Observe Diagnostics
  4. Observe render timeline

screen shot 2018-11-30 at 5 11 54 pm

screen shot 2018-11-30 at 5 12 03 pm

What is the current behavior?

  1. "All text remains visible during webfont loads" is Passing
  2. Red text is invisible for several frames in the render timeline
  3. Green text is always visible in the render timeline

What is the expected behavior?

  1. "Ensure text remains visible during webfont loads" should be Failing
  2. Red text is invisible for several frames in the render timeline
  3. Green text is always visible in the render timeline

Environment Information

  • Affected Channels: DevTools
  • Lighthouse version: 3.0.3 on Chrome 70.0.3538.102 (Official Build) (64-bit)
  • Node.js version: n/a
  • Operating System: OSX 10.14.1

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@patrickhulce

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patrickhulce commented Dec 1, 2018

Thanks for filing and for the example @amclin!

I'm not seeing this behavior on that URL though on latest Lighthouse, so I think we might have already fixed this...

image

@amclin

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amclin commented Dec 3, 2018

@patrickhulce actually, CLI Lighthouse also incorrectly passes this test when it should be failing the test:
I just ran 4.0.0-alpha.2-3.2.1 from the CLI and it reports "All text remains visible during webfont loads" which is incorrect:
screen shot 2018-12-03 at 2 11 40 pm

@patrickhulce

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patrickhulce commented Dec 3, 2018

@amclin 4.0.0-alpha.2-3.2.1 is just version 3.2.1 republished with the latest tag on NPM. We weren't quite ready to launch 4.0.0 afterall. I'm still seeing the failure on latest master.

@amclin

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amclin commented Dec 3, 2018

I'm happy to test further, but I'm not sure which branch/version you're considering this fixed. Here's 4.0.0-alpha.1 reporting a pass where it should fail:
screen shot 2018-12-03 at 2 26 03 pm

@patrickhulce

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patrickhulce commented Dec 3, 2018

Perhaps it's flaky, but latest is definitely not ignoring this font. Tested with (a203a36) I'm 3/3 on identifying it correctly as blocking.

image

@paulirish paulirish closed this Dec 17, 2018

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