Block API: Add support for block aliases (PoC)

src/wp-includes/class-wp-block-type-registry.php

@@ -22,6 +22,15 @@ final class WP_Block_Type_Registry {
 	 */
 	private $registered_block_types = array();
 
+
+	/**
+	 * Registered block aliases, as `$alias_name => $instance` pairs.
+	 *
+	 * @since 6.6.0
+	 * var WP_Block_Type[]
+	 */
+	private $registered_block_type_aliases = array();
+
 	/**
 	 * Container for the main instance of the class.
 	 *
@@ -94,6 +103,21 @@ public function register( $name, $args = array() ) {
 			$block_type = new WP_Block_Type( $name, $args );
 		}
 
+		// Register aliases for the block type.
+		$aliases = $block_type->get_aliases();
+		if ( ! empty( $aliases ) ) {
+			foreach ( $aliases as $alias_name => $alias_args ) {
+				if ( ! $this->is_registered( $alias_name ) ) {
+					$new_args                             = array_merge( $args, $alias_args );
+					$new_args['alias_of']                 = $name;
+					$alias_args['attributes']['metadata'] = array( 'canonicalBlock' => $name );
+
+					// Register the alias block.
+					$this->registered_block_type_aliases[ $alias_name ] = new WP_Block_Type( $alias_name, array_merge( $args, $alias_args ) );
+				}
+			}
+		}
+
 		$this->registered_block_types[ $name ] = $block_type;
 
 		return $block_type;
@@ -142,6 +166,10 @@ public function get_registered( $name ) {
 			return null;
 		}
 
+		if ( isset( $this->registered_block_type_aliases[ $name ] ) ) {
+			return $this->registered_block_type_aliases[ $name ];
+		}
+
 		return $this->registered_block_types[ $name ];
 	}
 
@@ -153,7 +181,7 @@ public function get_registered( $name ) {
 	 * @return WP_Block_Type[] Associative array of `$block_type_name => $block_type` pairs.
 	 */
 	public function get_all_registered() {
-		return $this->registered_block_types;
+		return array_merge( $this->registered_block_types, $this->registered_block_type_aliases );
 	}
 
 	/**
@@ -165,7 +193,7 @@ public function get_all_registered() {
 	 * @return bool True if the block type is registered, false otherwise.
 	 */
 	public function is_registered( $name ) {
-		return isset( $this->registered_block_types[ $name ] );
+		return isset( $this->registered_block_types[ $name ] ) || isset( $this->registered_block_type_aliases[ $name ] );
 	}
 
 	public function __wakeup() {

src/wp-includes/class-wp-block-type.php

@@ -134,6 +134,22 @@ class WP_Block_Type {
 	 */
 	public $variation_callback = null;
 
+	/**
+	 * List of aliases for this block type. Only accessible through magic getter. null by default.
+	 *
+	 * @since 6.6.0
+	 * @var array[]|null
+	 */
+	private $aliases = null;
+
+	/**
+	 * If this is an alias block type, this property will contain the name of the block type it is an alias of.
+	 *
+	 * @since 6.6.0
+	 * @var string
+	 */
+	public $alias_of = null;
+
 	/**
 	 * Custom CSS selectors for theme.json style generation.
 	 *
@@ -366,6 +382,10 @@ public function __get( $name ) {
 			return $this->get_variations();
 		}
 
+		if ( 'aliases' === $name ) {
+			return $this->get_aliases();
+		}
+
 		if ( 'uses_context' === $name ) {
 			return $this->get_uses_context();
 		}
@@ -616,6 +636,40 @@ public function get_variations() {
 		return apply_filters( 'get_block_type_variations', $this->variations, $this );
 	}
 
+	/**
+	 * Get block aliases.
+	 *
+	 * @since 6.6.0
+	 *
+	 * @return array[]
+	 */
+	public function get_aliases() {
+		if ( ! isset( $this->aliases ) ) {
+			$this->aliases = array();
+			$variations    = array();
+			if ( is_callable( $this->variation_callback ) ) {
+				$variations = call_user_func( $this->variation_callback );
+			}
+
+			foreach ( $variations as $variation ) {
+				if ( ! empty( $variation['alias'] ) && true === $variation['alias'] ) {
+					unset( $variation['alias'] );
+					$this->aliases[][ $variation['name'] ] = $variation;
+				}
+			}
+		}
+
+		/**
+		 * Filters the registered aliases for a block type.
+		 *
+		 * @since 6.6.0
+		 *
+		 * @param array         $aliases    Array of registered aliases for a block type.
+		 * @param WP_Block_Type $block_type The full block type object.
+		 */
+		return apply_filters( 'get_block_type_aliases', $this->aliases, $this );
+	}
+
 	/**
 	 * Get block uses context.
 	 *