REST API: Add block editor settings endpoint

[enej]

This is a tracking ticket for merging the block editor settings endpoints from Gutenberg.

​https://github.com/WordPress/gutenberg/blob/trunk/lib/class-wp-rest-block-editor-settings-controller.php

Trac ticket: https://core.trac.wordpress.org/ticket/54247

Thanks for the patch @enejb! We usually don't merge these until shortly before/alongside the corresponding JS. Is there a ticket for that already?

[enej]

More context:
This block-editor-settings endpoint first landed in ​https://github.com/WordPress/gutenberg/pull/29969

The main rationale behind the endpoint is to expose the block editor settings data so that it can be consumed by other editors in different contexts such as the mobile native editor, site editor, the front end.

Currently, the editor loads these settings on page load vs using this endpoint but there seems to be interest in using this endpoint in the future. (​https://github.com/WordPress/gutenberg/pull/29969#issuecomment-831785648)

This endpoint was first introduced as __experimental/wp-block-editor/v1 in gutenberg and later renamed to wp-block-editor/v1 in ​https://github.com/WordPress/gutenberg/pull/33128

Some rational behind wp/v2 vs wp-block-editor/v1 can be found in this comment ​https://github.com/WordPress/gutenberg/pull/33128#discussion_r662384172

Shipping this endpoint in 5.9 would mean that more folks that are using the mobile app block editor (not just sites running the latest version of Gutenberg) can benefit from the colour and font size options UI improvements.

Thanks for taking a look @TimothyBJacobs

I provided a bit more context here - https://core.trac.wordpress.org/ticket/54247#comment:4
As far as I can tell the endpoint is not being used yet directly by Gutenberg. (I couldn't find any calls being made to it)

cc @gziolo Do you know if there are any plans for using the endpoint in Gutenberg directly?

We are already using the endpoint in native mobile apps already in order to allow users to edit font size and colours on some blocks.

Do you know if there are any plans for using the endpoint in Gutenberg directly?

In theory we could since we print in PHP some JS code to pass the same settings to the editor. I’m not sure how the transition could look like in practice though. @oandregal or @jorgefilipecosta, any immediate plans related to that?

:wave: This is what I know: this endpoint landed at ​https://github.com/WordPress/gutenberg/pull/29969 in Gutenberg and it's used by mobile, so they'd know more if it's ready to be merged in WordPress core. @WordPress/native-mobile

While the endpoint was mainly driven by mobile needs to gather "global styles" data, it can do more as it stands. It was suggested that the editors could use this endpoint, but I'm not aware of any work in this direction. Additionally, @youknowriad is proposing we use a different one for global settings & styles at ​https://github.com/WordPress/gutenberg/discussions/35141 If we do so, I wonder if mobile should use it as well. Given that this is still being talked about, I'm not sure we should merge the existing settings endpoint.

If we do so, I wonder if mobile should use it as well.

Hey @oandregal 👋 It'd be nice to use it on mobile as well since we have plans to allow modifying global styles from the app, the thing is we also use __experimentalFeatures from the block editor settings endpoint. Would this new endpoint have this data as well?

Would you provide your thoughts on the discussion at ​https://github.com/WordPress/gutenberg/discussions/35141? If we go that route we need to cover the two use cases we have at the moment (mobile plus the site editor).

[andraganescu]

It looks like this would be a good addition to the API for the mobile app. Nevertheless it's unclear from ​here if that endpoint is "final" or a new one is in the works.