Block Hooks: Suppress insertion of hooked blocks in before/after position into post object content

src/wp-includes/blocks.php

@@ -1129,9 +1129,25 @@ function apply_block_hooks_to_content( $content, $context = null, $callback = 'i
 	 * We also need to cover the case where the hooked block is not present in
 	 * `$content` at first and we're allowed to insert it once -- but not again.
 	 */
-	$suppress_single_instance_blocks = static function ( $hooked_block_types ) use ( &$block_allows_multiple_instances, $content ) {
+	$suppress_single_instance_blocks = static function ( $hooked_block_types, $relative_position, $anchor_block_type ) use ( &$block_allows_multiple_instances, $content, $context ) {
 		static $single_instance_blocks_present_in_content = array();
 		foreach ( $hooked_block_types as $index => $hooked_block_type ) {
+			if ( $context instanceof WP_Post ) {
+				$wrapper_block_type = 'core/post-content';
+				if ( 'wp_navigation' === $context->post_type ) {
+					$wrapper_block_type = 'core/navigation';
+				} elseif ( 'wp_block' === $context->post_type ) {
+					$wrapper_block_type = 'core/block';
+				}
+
+				if (
+					$wrapper_block_type === $anchor_block_type &&
+					in_array( $relative_position, array( 'before', 'after' ), true )
+				) {
+					$hooked_block_types = array();
+				}
+			}
+
 			if ( ! isset( $block_allows_multiple_instances[ $hooked_block_type ] ) ) {
 				$hooked_block_type_definition =
 					WP_Block_Type_Registry::get_instance()->get_registered( $hooked_block_type );
@@ -1157,7 +1173,7 @@ function apply_block_hooks_to_content( $content, $context = null, $callback = 'i
 		}
 		return $hooked_block_types;
 	};
-	add_filter( 'hooked_block_types', $suppress_single_instance_blocks, PHP_INT_MAX );
+	add_filter( 'hooked_block_types', $suppress_single_instance_blocks, PHP_INT_MAX, 3 );
 	$content = traverse_and_serialize_blocks(
 		parse_blocks( $content ),
 		$before_block_visitor,

tests/phpunit/tests/blocks/applyBlockHooksToContentFromPostObject.php

@@ -88,6 +88,15 @@ public static function wpSetUpBeforeClass() {
 				),
 			)
 		);
+
+		register_block_type(
+			'tests/hooked-block-after-post-content',
+			array(
+				'block_hooks' => array(
+					'core/post-content' => 'after',
+				),
+			)
+		);
 	}
 
 	/**
@@ -100,6 +109,7 @@ public static function wpTearDownAfterClass() {
 
 		$registry->unregister( 'tests/hooked-block' );
 		$registry->unregister( 'tests/hooked-block-first-child' );
+		$registry->unregister( 'tests/hooked-block-after-post-content' );
 	}
 
 	/**