Fix rel="me" not being added to pre-linked Extra Fields URLs

[pfefferle]

Fixes #2832

Related to #1441

Proposed changes:

• Fix rel="me" not being added to Extra Fields links that are already wrapped in <a> tags (e.g., from the block editor)
• Add new add_rel_me_to_links() method that uses WP_HTML_Tag_Processor to inject "me" into the rel attribute of all links
• Both PropertyValue HTML and Link attachments now include rel="me" for proper Mastodon/fediverse verification

Background

When users create Extra Fields using the block editor, URLs are often already wrapped in <a> tags before the activitypub_link_rel filter runs. These pre-linked URLs bypassed the filter, resulting in no rel="me" attribute being added.

Before (broken):

{"type":"Link","name":"Blog","href":"https://example.com","rel":["nofollow","noopener"]}

After (fixed):

{"type":"Link","name":"Blog","href":"https://example.com","rel":["nofollow","noopener","me"]}

Other information:

• Have you written new tests for your changes, if applicable?

Testing instructions:

1. Create an Extra Field for a user or blog actor
2. In the block editor, add a link (not a plain URL, but an actual <a> tag link)
3. Save the Extra Field
4. Fetch the actor JSON: curl -H "Accept: application/activity+json" https://yoursite.com/@username
5. Verify the attachment includes rel: ["me"] in the Link type and rel="me" in the PropertyValue HTML

Changelog entry

• Automatically create a changelog entry from the details below.

Changelog Entry Details

Significance

• Patch

Type

• Fixed - for any bug fixes

Message

Ensure Extra Fields links always include rel="me" for Mastodon verification.

[Copilot]

Pull request overview

This PR fixes an issue where rel="me" attributes were not being added to Extra Fields URLs that were already wrapped in <a> tags (e.g., from the block editor), preventing proper Mastodon/fediverse verification.

Changes:

• Added add_rel_me_to_links() method using WP_HTML_Tag_Processor to inject "me" into rel attributes of existing links
• Updated fields_to_attachments() to process content through the new method before creating attachments
• Added comprehensive test coverage for pre-linked URLs with various rel attribute scenarios

Reviewed changes

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

File	Description
includes/collection/class-extra-fields.php	Implements new add_rel_me_to_links() method and integrates it into the attachment generation flow
tests/phpunit/tests/includes/collection/class-test-extra-fields.php	Adds three test cases covering pre-linked URLs without rel, with existing rel, and with existing rel="me"
.github/changelog/2874-from-description	Adds changelog entry documenting the bug fix

[Copilot]

This test logic is fragile and could produce false positives. It counts occurrences of ' me' and '"me' separately, which could match unintended strings like 'some' or 'home'. A more reliable approach would be to parse the rel attribute value and count 'me' as a distinct token within it, or use a regex that specifically matches 'me' as a word boundary within the rel attribute.

Suggested change

	// PropertyValue should have "me" exactly once in the HTML.
	$this->assertEquals( 1, \substr_count( $attachments[0]['value'], ' me' ) + \substr_count( $attachments[0]['value'], '"me' ) );
	// PropertyValue should have "me" exactly once in the rel attribute.
	$rel_match = array();
	\preg_match( '/\brel="([^"]*)"/', $attachments[0]['value'], $rel_match );
	$rel_value = isset( $rel_match[1] ) ? $rel_match[1] : '';
	$this->assertEquals( 1, \preg_match_all( '/\bme\b/', $rel_value ) );

[Copilot]

The rel attribute value should be trimmed before exploding to handle cases where the attribute has leading/trailing whitespace (e.g., rel=' nofollow noopener '). Without trimming, explode will create empty string elements that could cause issues. Use trim( $rel ) before splitting.

Suggested change

	$rel_parts = $rel && \is_string( $rel ) ? \explode( ' ', $rel ) : array();
	$rel_parts = $rel && \is_string( $rel ) ? \explode( ' ', \trim( $rel ) ) : array();