cc @oandregal @gziolo if you could help me double check this

I've compared the changes with core and it looks good. I'm trying to find the tests instructions in older PRs.

This is what I've done for testing (updated from #306):

• Check out this PR locally and cd to the directory.
• composer install
• Update the THEME_JSON_SOURCE to be empty in this line at the JsonSchemaExtractor class, so the command uses the local backup file defined by THEME_JSON_FALLBACK.
• Create a new directory called foo-theme that contains a theme.json file and paste the content of TwentyTwentyThree's theme.json.
• Run vendor/bin/wp i18n make-pot foo-theme
• Verify that there's a foo-theme/foo-theme.pot file and that strings and their context are present (look for "Custom template name", "Template part name", "Font family name", "Space size name", the ones added in this PR).

I've also run composer behat -- features/makepot.feature though the scenario 001 Scenario: Extract all supported functions failed. Same as in trunk, so unrelated to this PR.

Awesome, thanks for testing! 🎉

Totally forgot that this is just the backup file. That makes the change way less urgent 🙂

I'll see if I can reproduce that test failure locally.

We really need a better way to keep this file in sync with core.

We can add a GHA that replaces the included file with the one on SVN and creates a PR if changes have been detected.

@schlessera Good idea. Just added such a workflow now.