Fix infinite loop when calling wp_get_upload_dir in a function that's used to filter font_dir

[matiasbenedetto]

ℹ️ Porting WordPress/gutenberg#58839 already merged in from Gutenberg repo.

What?

Fix infinite loop when calling wp_get_upload_dir in a function that's used to filter font_dir.
An alternative approach to: #6198

Why?

This avoids an infinite loop that can occur if wp_upload_dir() is called inside a 'font_dir' callback.

Testing instructions

1. Use wp_get_upload_dir() inside a function used to filter upload_dir as in the following example:

 function alter_wp_fonts_dir( $defaults ) {
	$wp_upload_dir = wp_get_upload_dir();
	$uploads_basedir = $wp_upload_dir['basedir'];
	$uploads_baseurl = $wp_upload_dir['baseurl'];

	$fonts_dir = $uploads_basedir . '/fonts';
	// Generate the URL for the fonts directory from the font dir.
	$fonts_url = str_replace( $uploads_basedir, $uploads_baseurl, $fonts_dir );

	$defaults['path'] = $fonts_dir;
	$defaults['url']  = $fonts_url;

	return $defaults;
}
add_filter( 'font_dir', 'alter_wp_fonts_dir' );

2. Upload fonts using the font library
3. Check that the fonts were successfully uploaded to the path set by the filter.
   (wp-content/uploads/fonts in the example provided).

---

Trac ticket: https://core.trac.wordpress.org/ticket/60652

[github-actions]

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Props mmaattiiaass, ironprogrammer.

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[github-actions]

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[ironprogrammer]

Test Report

Environment

• System: MacBook Pro Apple M1 Pro, macOS 14.3.1
• Browser: Safari 17.3.1
• Server: nginx/1.25.4, PHP 8.2.16, MySQL 8.0.27
• WordPress: 6.5-beta3-57723-src
• Theme: twentytwentyfour v1.0
• Active Plugins:
  • font-dir-mover (mu-plugin with sample font_dir filter code)

Actual Results

• ✅ Fonts saved successfully to relocated font storage directory, wp-content/uploads/fonts (+directory creation was successful).

Supplemental Artifacts

Figure 1: Before patch.

Figure 2: After patch.

Figure 3: Source URL after patch.

[ironprogrammer]

Thanks for the PR, @matiasbenedetto! Just a nit on comment spacing here.

[youknowriad]

Commit https://core.trac.wordpress.org/changeset/57740