Deactivating a theme font removes it from the Font Library

[creativecoder]

Description

After de-activating a theme font variant (font face), it no longer appears in the Font Library modal.

Step-by-step reproduction instructions

Using the TT4 theme

• In the Site editor, open the Font Library modal, and click on one of the "Theme Fonts" in the list of fonts.
• Uncheck one of the variants, and click "Update"
• Close the modal and open it again, returning the same font
• The font you unchecked is no longer in the list of font variants
• If the theme font only has one variant and you uncheck it, the font is no longer in the Theme Fonts list

Screenshots, screen recording, code snippet

https://github.com/WordPress/gutenberg/assets/1699996/02a26a99-e0b6-4d09-8d80-b061668257a7

Environment info

• WP: 6.6-alpha-57778-src, Gutenberg: 18.0.0, TT4
• Firefox
• Desktop w/ macOS

Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

Yes

[t-hamano]

I was able to reproduce it on WordPress 6.5 without the Gutenberg plugin enabled.

Also, I noticed the following:

• Once I disable all variations of that theme font, all variations will be displayed again.
• Does not occur with Google fonts

https://github.com/WordPress/gutenberg/assets/54422211/d59ec5d4-f051-4115-90cb-c58af8ff88fb

[matiasbenedetto]

This behavior is forced by the fact that we can't easily know which are the base fonts when a theme style variation is added to the global styles. When a theme style variation is added to the Global Styles, the 'base' theme fonts coming from the theme.json file are no longer relevant, but we can't use the style variation as 'base' because there's no indication of which the theme variant active is.