Exclude the canonical link from the "Relative protocol" setting to avoid SEO issues

[DahmaniAdame]

Before submitting an issue please check that you’ve completed the following steps:

• Made sure you’re on the latest version 3.12.5.3
• Used the search feature to ensure that the bug hasn’t been reported before

Describe the bug
When the setting under the Cloudflare add-on Relative protocol is used, we change the canonical URL from:

<link rel="canonical" href="https://domain.ext/">

to

<link rel="canonical" href="//domain.ext/">

This will result Lighthouse to prompt the following recommendation when auditing the SEO part:

Document does not have a valid rel=canonicalIs not an absolute URL (//domain.ext/)

Changing the following regex found here:

wp-rocket/inc/front/protocol.php

Line 28 in 0dd1e1f

$re = "/(<(script|link|img|form)([^>]*)(href|src|action)=[\"'])https?:\\/\\//i";

to exclude the canonical rel will fix the issue.

Something like the following should work:

/(<(script|link|img|form)(?!.*?\bcanonical\b)([^>]*)(href|src|action)=[\"'])https?:\\/\\//i

To Reproduce
Steps to reproduce the behavior:

1. Enable the "Relative protocol" under Cloudflare add-on
2. Do an SEO audit on Lighthouse
3. See error

Expected behavior
There shouldn't be any results when the Relative protocol setting is enabled.

Screenshots
N/A

Additional context
N/A

Backlog Grooming (for WP Media dev team use only)

• Reproduce the problem
• Identify the root cause
• Scope a solution
• Estimate the effort

[CrochetFeve0251]

Reproduce the problem

Ok

Identify the root cause

Done by @DahmaniAdame

Scope a solution

The solution from @DahmaniAdame is valid but @piotrbak do you think we should make the regex more precise with a regex checking for rel="canonical" to prevent exclusion from img that possibly have a class contaning canonical?

Estimate the effort

Effort xs