Backport #2576 to Gutenberg

[anton-vlasenko]

What?

This PR aims to backport changes from WordPress/wordpress-develop#2576 to Gutenberg.

Fixes #40824.

Why?

This is needed to keep Core and Gutenberg as compatible as possible.

Testing Instructions

1. Make sure you are using WordPress 5.9.x
2. Enable Gutenberg.
3. Install this plugin to allow basic authorization for REST API requests.
4. Activate the plugin.
5. Send a GET request to your WordPress instance, e.g.:

curl --user username:password "http://wordpress.test/wp-json/wp/v2/block-patterns/patterns"

Replace

username:user_password

with the actual credentials.
Replace

http://your.wordpress.instance

with the actual URL of your instance.
6. Note the response. It must contain block patterns.

[jorgefilipecosta]

Hi @anton-vlasenko,
By accident on #41791, I needed another change to the pattern endpoint and ended up doing the objective of this PR.

I think we need a new file for the patterns endpoint. The changes in lib/compat/wordpress-6.0/class-wp-rest-block-patterns-controller.php don't have a practical effect because the file is not used at all if the core already includes the class:

	if ( ! class_exists( 'WP_REST_Block_Patterns_Controller' ) ) {
		require_once __DIR__ . '/compat/wordpress-6.0/class-wp-rest-block-patterns-controller.php';
	}

So when we need to change the endpoint in the plugin we will not be able to do so because this file is ignored.

In I'm creating a new file lib/compat/wordpress-6.1/class-gutenberg-rest-block-patterns-controller.php that contains a new class Gutenberg_REST_Block_Patterns_Controller overwriting the core one during the backports we just need to pass the class to the core and change its name. So in the plugin, we are free to apply the multiple changes we will need on the endpoint. If you prefer I can extract these changes to the endpoint in a separate PR so we can review the approach.

[TimothyBJacobs]

I think we need a new file for the patterns endpoint. The changes in lib/compat/wordpress-6.0/class-wp-rest-block-patterns-controller.php don't have a practical effect because the file is not used at all if the core already includes the class:

I believe that's the desired behavior here. This PR adjusts the included compat controller to behave the same way that Core behaves, so users running the plugin on WP 5.9 have identical behavior.

[jorgefilipecosta]

LGTM 👍 We can and should change lib/compat/wordpress-6.0/class-wp-rest-block-patterns-controller.php to match core although on #41791 I'm adding a new Gutenberg class so we can extend the core. I guess both PRs can be merged. And after both are merged we can just remove this file and start relying on the Gutenberg one.

[anton-vlasenko]

Hi @jorgefilipecosta
Thank you for getting to the bottom of the issue.
I haven't had a chance to review your PR yet, but the reasoning to change the class name looks completely valid to me.