Blocks: Introduce helper function to retrieve hooked blocks

src/wp-includes/blocks.php

@@ -739,6 +739,27 @@ function get_dynamic_block_names() {
 	return $dynamic_block_names;
 }
 
+/**
+ * Retrieves block types (and positions) hooked into the given block.
+ *
+ * @since 6.4.0
+ *
+ * @param string $name Block type name including namespace.
+ * @return array Associative array of `$block_type_name => $position` pairs.
+ */
+function get_hooked_blocks( $name ) {
+	$block_types = WP_Block_Type_Registry::get_instance()->get_all_registered();
+	$hooked_blocks = array();
+	foreach ( $block_types as $block_type ) {
+		foreach ( $block_type->block_hooks as $anchor_block_type => $relative_position ) {
+			if ( $anchor_block_type === $name ) {
+				$hooked_blocks[ $block_type->name ] = $relative_position;
+			}
+		}
+	}
+	return $hooked_blocks;
+}
+
 /**
  * Given an array of attributes, returns a string in the serialized attributes
  * format prepared for post content.

tests/phpunit/tests/blocks/blockHooks.php

@@ -0,0 +1,100 @@
+<?php
+/**
+ * Tests for block hooks feature functions.
+ *
+ * @package WordPress
+ * @subpackage Blocks
+ *
+ * @since 6.4.0
+ *
+ * @group blocks
+ */
+class Tests_Blocks_BlockHooks extends WP_UnitTestCase {
+
+	/**
+	 * Tear down after each test.
+	 *
+	 * @since 6.4.0
+	 */
+	public function tear_down() {
+		$registry = WP_Block_Type_Registry::get_instance();
+
+		foreach ( array( 'tests/my-block', 'tests/my-container-block' ) as $block_name ) {
+			if ( $registry->is_registered( $block_name ) ) {
+				$registry->unregister( $block_name );
+			}
+		}
+
+		parent::tear_down();
+	}
+
+	/**
+	 * @ticket 59383
+	 *
+	 * @covers ::get_hooked_blocks
+	 */
+	public function test_get_hooked_blocks_no_match_found() {
+		$result = get_hooked_blocks( 'tests/no-hooked-blocks' );
+
+		$this->assertSame( array(), $result );
+	}
+
+	/**
+	 * @ticket 59383
+	 *
+	 * @covers ::get_hooked_blocks
+	 */
+	public function test_get_hooked_blocks_matches_found() {
+		register_block_type(
+			'tests/injected-one',
+			array(
+				'block_hooks' => array(
+					'tests/hooked-at-before' => 'before',
+					'tests/hooked-at-after'  => 'after',
+				),
+			)
+		);
+		register_block_type(
+			'tests/injected-two',
+			array(
+				'block_hooks' => array(
+					'tests/hooked-at-before'      => 'before',
+					'tests/hooked-at-after'       => 'after',
+					'tests/hooked-at-first-child' => 'first_child',
+					'tests/hooked-at-last-child'  => 'last_child',
+				),
+			)
+		);
+
+		$this->assertSame(
+			array(
+				'tests/injected-one' => 'before',
+				'tests/injected-two' => 'before',
+			),
+			get_hooked_blocks( 'tests/hooked-at-before' ),
+			'block hooked at the before position'
+		);
+		$this->assertSame(
+			array(
+				'tests/injected-one' => 'after',
+				'tests/injected-two' => 'after',
+			),
+			get_hooked_blocks( 'tests/hooked-at-after' ),
+			'block hooked at the after position'
+		);
+		$this->assertSame(
+			array(
+				'tests/injected-two' => 'first_child',
+			),
+			get_hooked_blocks( 'tests/hooked-at-first-child' ),
+			'block hooked at the first child position'
+		);
+		$this->assertSame(
+			array(
+				'tests/injected-two' => 'last_child',
+			),
+			get_hooked_blocks( 'tests/hooked-at-last-child' ),
+			'block hooked at the last child position'
+		);
+	}
+}