3.7: External CSS Minify exclusions are not working as intended

[webtrainingwheels]

The specs for excluding an external CSS file from minify are:

3rd Party: Use either the full URL path or only the domain name, to exclude external CSS.

However there are some cases where this is not working as expected.

Samples:

• https://use.fontawesome.com/releases/v5.14.0/css/all.css
  Had to be excluded like this: /releases/v5.14.0/css/all.css

• https://cloud.typography.com/7231672/6270372/css/fonts.css
  Had to be excluded like this: /7231672/6270372/css/fonts.css

Seems only to be an issue with Minify, not Combine

Tickets:

• https://secure.helpscout.net/conversation/1281498132/194658?folderId=3572910
• https://secure.helpscout.net/conversation/1278389385/193723?folderId=2675957

To Reproduce
Steps to reproduce the behavior:

1. Include one of the above URLS in the HTML of a site
2. Enable Minify CSS
3. Try to exclude the file with either the domain or full URL

Expected behavior
The files should be excluded using either the domain or full URL

Backlog Grooming (for WP Media dev team use only)

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

[vmanthos]

Related ticket: https://secure.helpscout.net/conversation/1310458122/202765?folderId=2135277

I further investigated this.

This is because of the preg_match() we run here:

wp-rocket/inc/Engine/Optimization/Minify/CSS/AbstractCSSOptimization.php

Line 141 in 6c811c1

if ( preg_match( '#^(' . $this->excluded_files . ')$#', $file_path ) ) {

If the excluded file is e.g. cdn.jsdelivr.net/npm/bootstrap@4.5.3/dist/css/bootstrap.min.css, the $file_path is /npm/bootstrap@4.5.3/dist/css/bootstrap.min.css, and preg_match() returns 0.

Hence the file is not excluded and is cached locally.

[vmanthos]

Related ticket: https://secure.helpscout.net/conversation/1308669776/202288/

[iCaspar]

• Can Reproduce

• Identified cause: per @vmanthos, the regex fails to identify domain names. [X]

Scope Solution:

• Add testcases for domain names and full URLs to fixtures for inc/Engine/Optimization/Minify/CSS/Minify
• Make tests pass by adjusting regex for preg_match() in AbsstractCSSOptimization::is_minify_excluded_file()

Estimated Effort:

• [S]