[WP 6.1] Fluid and spacing settings in theme.json are lost when theme export

[mayuge3]

Description

When I use theme export,

• settings.spacing.spacingScale.steps -> field is lost
• settings.spacing.spacingSizes.slug -> quotation is lost
• settings.typography.fluid -> field is lost

Step-by-step reproduction instructions

1. Use WP 6.1 nightly and Twenty Twenty Three without gutenberg plugin
2. Go to the site editor.
3. Select Three dots menu > Export

Screenshots, screen recording, code snippet

spacing before export:

spacing after export:

fluid before export:

fluid after export:

Environment info

WP 6.1 (latest nightly via Beta Tester plugin), instawp install
TT3 included in WP 6.1 nightly.
Gutenberg plugin deactivated

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

[glendaviesnz]

I have a fix for the spacingScale value here, still trying to work out the fluid font value as it isn't related and only happens in 6.1, not GB trunk

[glendaviesnz]

The fluid flag was a different issue and a potential fix for it is here

[ramonjd]

Thank you @mayuge3 Also reported in https://core.trac.wordpress.org/ticket/56684 Props to you!

[mayuge3]

Thank you!

I'm not familiar with technical details, so I opened another issue #214 at TT3, is it related to this issue's fluid problem...?

[dream-encode]

I was looking to merge this, but I want to make sure this comment by @tellthemachines is addressed in the final PR:
#44555 (review)

[glendaviesnz]

but I want to make sure this comment by @tellthemachines is addressed in the final PR

thanks @dream-encode, I will look at the issue with casting to ints on a separate PR as it will be a bit trickier to resolve and test.

[ndiego]

@glendaviesnz I just wanted to confirm that this issue is all set, given the merged and closed PRs. I noticed the issue still had the Backport label, so I wanted to double check before I removed it. Thanks!

[glendaviesnz]

Thanks @ndiego, have removed the label now.