Fix #7417: Preload fonts external domains exclusions

[Miraeld]

Description

Fixes #7417 from WP Rocket repo
Refer to wp-media/wp-rocket#7519

Type of change

• Enhancement (non-breaking change which improves an existing functionality).

Detailed scenario

What was tested

Implemented test scenarios:

1. Origin-Based External Domain Filtering

✅ External CSS links from different origins (e.g., fonts.googleapis.com) are correctly identified and processed
✅ Same-origin CSS links are properly excluded from external font processing
✅ Proper window.location.href mocking ensures accurate origin comparison in test environment
2. Exclusion-Based Configuration

✅ Links matching external_font_exclusions patterns are correctly filtered out
✅ Empty exclusion arrays default to processing all external domains
✅ Substring matching works correctly for exclusion patterns

How to test

Refer to wp-media/wp-rocket#7519

Technical description

Documentation

This pull request refactors the logic for processing external font stylesheets in the BeaconPreloadFonts class, replacing the allowlist-based approach with an exclusion-based approach. It also updates the test suite to ensure the new behavior is properly validated. The most important changes include the introduction of the external_font_exclusions configuration, enhancements to origin checks for external links, and the addition of new test cases to cover the updated functionality.

Updates to font processing logic:

• Replaced the allowlist of external font domains with an exclusion-based approach using a new external_font_exclusions configuration. This change ensures that all external CSS links are processed unless explicitly excluded. (src/BeaconPreloadFonts.js, src/BeaconPreloadFonts.jsL261-R280)

Enhancements to origin checks:

• Added logic to verify that only external domains (different origins) are processed, improving robustness and security. This includes handling potential errors when parsing URLs. (src/BeaconPreloadFonts.js, src/BeaconPreloadFonts.jsL261-R280)

Test suite updates:

• Introduced the external_font_exclusions property in the test configuration to validate the exclusion-based filtering mechanism. (test/BeaconPreloadFonts.test.js, test/BeaconPreloadFonts.test.jsL37-R38)
• Added tests to ensure links are excluded based on the external_font_exclusions configuration and that only links from different origins are processed. (test/BeaconPreloadFonts.test.js, test/BeaconPreloadFonts.test.jsR1232-R1267)
• Mocked window.location and the URL constructor in tests to simulate origin checks and ensure accurate comparisons. (test/BeaconPreloadFonts.test.js, [1] [2]

New dependencies

None

Risks

None

Mandatory Checklist

Code validation

• I validated all the Acceptance Criteria. If possible, provide screenshots or videos.
• I triggered all changed lines of code at least once without new errors/warnings/notices.
• I implemented built-in tests to cover the new/changed code.

Code style

• I wrote a self-explanatory code about what it does.
• I protected entry points against unexpected inputs.
• I did not introduce unnecessary complexity.
• Output messages (errors, notices, logs) are explicit enough for users to understand the issue and are actionnable.

[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
✅ -0.05% (target: -1.00%)	✅ 89.47% (target: 50.00%)

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (3be7674)	1905	1582	83.04%
Head commit (ba38b29)	1911 (+6)	1586 (+4)	82.99% (-0.05%)

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#63)	19	17	89.47%

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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[Copilot]

Pull Request Overview

This PR refactors the external font processing logic in the BeaconPreloadFonts class from an allowlist-based approach to an exclusion-based approach, addressing issue #7417. The change enables processing of all external CSS links from different origins unless they are explicitly excluded through the new external_font_exclusions configuration.

• Replaced hardcoded allowlist of font providers with configurable exclusion-based filtering
• Added origin validation to ensure only external domains are processed
• Enhanced test coverage with origin mocking and exclusion-based test scenarios

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
src/BeaconPreloadFonts.js	Replaced allowlist filtering with exclusion-based logic and added origin validation for external CSS links
test/BeaconPreloadFonts.test.js	Added external_font_exclusions config property and comprehensive tests for origin filtering and exclusion behavior