Fixes #55879

What?

This PR fixes an issue where local fonts or Google fonts installation fails.

Why?

When I traced the cause, I found that it was caused by #54829. The error also occurs because has_write_permission() is false at this location.

The has_write_permission() method checks whether the font directory (/path-to/wp-content/fonts) is writable.
However, if you have never installed any fonts, the fonts directory does not exist and is considered unwritable.

Before the change in #54829, wp_upload_dir()['basedir'] (/path/to/wp-content/uploads) was checked to see if it was writable, which is not the actual directory where the fonts would be written. In most cases the uploads directory will be writable, so the has_write_permission() method will return true and the font will be installed unintentionally.

How?

Originally, I think we should install the font after all checks below have passed.

• Does the fonts directory exist?
• If the fonts directory does not exist, try to create it and check whether the directory was created successfully
• Is the fonts directory writable?

I reflected all these conditions in the logic.

Testing Instructions

Pattern 1

• If the /path/to/wp-content/fonts directory exists, please delete it.
• Try installing the font.
• The fonts directory will be created and the font installation should be successful.

Pattern 2

• Delete /path/to/wp-content/fonts directory.
• Make the /path-to/wp-content directory non-writable with the following command: chmod a-w /path/to/wp-content
• Try installing the font.
• The installation should fail and return a 500 error (cannot_create_fonts_folder).

Pattern 3

• Make the /path/to/wp-content directory writable again with the following command: chmod 755 /path/to/wp-content
• Create path/to/wp-content/fonts dorectory
• Make the /path-to/wp-content/fonts directory non-writable with the following command: chmod a-w /path/to/wp-content/fonts
• Try installing the font.
• The installation should fail and return a 500 error (cannot_write_fonts_folder).