Enhancement: Page speed metrics in preview

[adamsilverstein]

Originally proposed and discussed in WordPress/gutenberg#33578 - the discussion there proposed starting with adding this to the Performance Lab plugin first.

What problem does this address?

When publishing or updating a post, users check the preview screen to see how their page will look. If might help users if they could get a sense of how their page would perform.

What is your proposed solution?

• when users preview a page, send an API request to the Lighthouse or a similar API with a preview URL
• unpublished posts could be previewed with a temporary token, or left off
• visually display a simple score for the page, perhaps linking to the full report

Questions

Does this type of feature belong in a plugin? I would love to hear from the project maintainers if they think this type of feature can be built into Gutenberg directly or is better served by plugins? I believe existing filters would provide everything a plugin would need to add such a feature.

[adamsilverstein]

@westonruter Do you think this belongs in the "main" plugin, or should we consider a new plugin? Maybe we could do something like "Performance Checks" that could include things like this proposed preview check and maybe the general health checks we have as well.

[westonruter]

@adamsilverstein I think it belongs in the main plugin, yeah. In this way, it is similar to Server-Timing and the Site Health checks (#1781 notwithstanding).