Collaboration: Gate db_error on WP_DEBUG and fix JSON decode inconsistency

- Only include $wpdb->last_error in REST error responses when WP_DEBUG
  is true, matching core REST API conventions and preventing table/column
  name leakage on production sites
- Normalize JSON decode validation in get_updates_after_cursor() to use
  is_array() instead of json_last_error(), consistent with
  get_awareness_state() in the same class

Author: josephfusco

src/wp-includes/collaboration/class-wp-collaboration-table-storage.php

@@ -202,7 +202,7 @@ public function get_updates_after_cursor( string $room, int $cursor ): array {
 		$updates = array();
 		foreach ( $rows as $row ) {
 			$decoded = json_decode( $row->update_value, true );
-			if ( json_last_error() === JSON_ERROR_NONE ) {
+			if ( is_array( $decoded ) ) {
 				$updates[] = $decoded;
 			}
 		}

src/wp-includes/collaboration/class-wp-http-polling-collaboration-server.php

@@ -453,13 +453,14 @@ private function process_collaboration_update( string $room, int $client_id, int
 				if ( ! $has_newer_compaction ) {
 					if ( ! $this->storage->remove_updates_before_cursor( $room, $cursor ) ) {
 						global $wpdb;
+						$data = array( 'status' => 500 );
+						if ( defined( 'WP_DEBUG' ) && WP_DEBUG ) {
+							$data['db_error'] = $wpdb->last_error;
+						}
 						return new WP_Error(
 							'rest_collaboration_storage_error',
 							__( 'Failed to remove updates during compaction.' ),
-							array(
-								'status'   => 500,
-								'db_error' => $wpdb->last_error,
-							)
+							$data
 						);
 					}
 
@@ -512,13 +513,14 @@ private function add_update( string $room, int $client_id, string $type, string
 
 		if ( ! $this->storage->add_update( $room, $update ) ) {
 			global $wpdb;
+			$data = array( 'status' => 500 );
+			if ( defined( 'WP_DEBUG' ) && WP_DEBUG ) {
+				$data['db_error'] = $wpdb->last_error;
+			}
 			return new WP_Error(
 				'rest_collaboration_storage_error',
 				__( 'Failed to store collaboration update.' ),
-				array(
-					'status'   => 500,
-					'db_error' => $wpdb->last_error,
-				)
+				$data
 			);
 		}