Global Styles in WordPress 5.7

[oandregal]

This issue describes what it entails to land the "Global Styles" project in WordPress core. The project has two main functions: 1) allows themes to control the editor settings via theme.json, and 2) creates a mechanism that coordinates core, theme, and user styles.

• Control editor settings: to land as part of 5.7.
• Style mechanism: while it works without a UI (this is, without user styles), the plan is to land this part paired with the UI (sidebar at edit-site) to make sure the underlying APIs match the UI needs.

Tasks

• Consolidate shape of theme.json file (implement the parts of Updates to experimental-theme.json #28163 that are required)
  • Settings as top-level key Update theme.json shape: make settings & style top-level keys #28110
  • Split global into * and root. Update theme.json: split global block selector into root and defaults #28533
  • WORK IN PROGRESS ― i18n, land Global Styles: Use context when translating entries in theme.json #28246
• Questions:
  • How to expand the behavior from the plugin: either implementing hooks (Add extensibility hooks to global styles infrastructure #27504 and proof of concept at Add hooks to modify theme.json structure #27722) or unregister what comes with core & use the plugin's code.
  • We don't need to implement the full spec at Updates to experimental-theme.json #28163 (control design tools visibility) but we need to make sure that what we land in 5.7 in terms of visibility of controls is in line with the spec and can be upgraded in 5.8.

Affected files

• lib/editor-settings.php => land gutenberg_get_common_block_editor_settings so other editors don't need to repeat the same logic.
• lib/experimental-theme.json => land the parts of it that affect settings.
• lib/class-wp-theme-json.php => land the parts of it that affect settings.
• lib/class-wp-theme-json-resolver.php => land the parts of it that affect settings. e.g.: do not expose user-origin methods as that something that only makes sense for styles at the moment.
• lib/global-styles.php => land gutenberg_experimental_global_styles_settings (but only the settings logic, not the styles)
• phpunit/class-wp-theme-json-test.php => land the tests related to settings and schema validation.
• phpunit/class-wp-theme-json-legacy-settings-test.php => to be paired with lib/global-styles.php

[oandregal]

I've removed the following two tasks from being blockers as they seem to be addressable after landing (if/when need it):

• Make global styles settings stable #27505 Make global styles settings stable.
• Handle an evolving theme.json shape (consider add versioning). #27230 Versioning theme.json shape.

[oandregal]

Removed #25612 from being a blocker. Can be added later.

[oandregal]

I've confirmed with @swissspidy that the structure for i18n-theme.json to be updated in #28110 together with #28246 is fine from a wp-cli perspective.

[oandregal]

#28533 is ready for review.

[swissspidy]

I've confirmed with @swissspidy that the structure for i18n-theme.json to be updated in #28110 together with #28246 is fine from a wp-cli perspective.

pinging @schlessera and @ocean90 for review just in case

[oandregal]

The latest can be reviewed on master: https://github.com/WordPress/gutenberg/blob/master/lib/experimental-i18n-theme.json I don't think I have to do any other modifications for the work in this issue, but happy to iterate and accomodate any other needs.