Blocks: short-circuit early on sites that do not support blocks (#431)

* Blocks: short-circuit early on sites that do not support blocks

Fixes #430

This is typically only the case for sites using a custom version of WordPress, like ClassicPress.

* let grunt build the markdown

* Check for block support earlier and add filter

One can now deactivate the blocks registered by ActivityPub like so:

```
add_filter( 'activitypub_site_supports_blocks', '__return_false' );
```

* Fix readme (gotta remember to use grunt)

* alias function

---------

Co-authored-by: Matthias Pfefferle <pfefferle@users.noreply.github.com>

README.md

@@ -107,6 +107,8 @@ Project maintained on GitHub at [automattic/wordpress-activitypub](https://githu
 
 ### Next ###
 
+* Compatibility: allow deactivating blocks registered by the plugin.
+* Compatibility: avoid Fatal Errors when using ClassicPress.
 * Fixed: fix a typo in a hook name.
 
 ### 1.0.0 ###

activitypub.php

@@ -15,6 +15,8 @@
 
 namespace Activitypub;
 
+use function Activitypub\site_supports_blocks;
+
 \defined( 'ACTIVITYPUB_REST_NAMESPACE' ) || \define( 'ACTIVITYPUB_REST_NAMESPACE', 'activitypub/1.0' );
 
 /**
@@ -52,10 +54,13 @@ function init() {
 	Admin::init();
 	Hashtag::init();
 	Shortcodes::init();
-	Blocks::init();
 	Mention::init();
 	Health_Check::init();
 	Scheduler::init();
+
+	if ( site_supports_blocks() ) {
+		Blocks::init();
+	}
 }
 \add_action( 'init', __NAMESPACE__ . '\init' );
 

includes/functions.php

@@ -457,3 +457,22 @@ if ( ! function_exists( 'get_self_link' ) ) {
 		return esc_url( apply_filters( 'self_link', set_url_scheme( 'http://' . $host['host'] . $path ) ) );
 	}
 }
+
+/**
+ * Check if a site supports the block editor.
+ *
+ * @return boolean True if the site supports the block editor, false otherwise.
+ */
+function site_supports_blocks() {
+	if ( ! \function_exists( 'register_block_type_from_metadata' ) ) {
+		return false;
+	}
+
+	/**
+	 * Allow plugins to disable block editor support,
+	 * thus disabling blocks registered by the ActivityPub plugin.
+	 *
+	 * @param boolean $supports_blocks True if the site supports the block editor, false otherwise.
+	 */
+	return apply_filters( 'activitypub_site_supports_blocks', true );
+}

readme.txt

@@ -107,6 +107,8 @@ Project maintained on GitHub at [automattic/wordpress-activitypub](https://githu
 
 = Next =
 
+* Compatibility: allow deactivating blocks registered by the plugin.
+* Compatibility: avoid Fatal Errors when using ClassicPress.
 * Fixed: fix a typo in a hook name.
 
 = 1.0.0 =