Fix: field drag-and-drop reorder throws "Unknown field" RuntimeException

The REDIPS drag-and-drop library sends 1-based DOM row indices as
old_order/new_order, but reorder.php treated them as database ranking
values. When rankings have gaps (from deletions or prior reorders),
DOM indices diverge from stored rankings, causing the query
`WHERE ranking = old_order` to find no matching field.

Refactor reorder.php to accept positional indices: retrieve all fields
ordered by ranking ASC, map them to 1-based positions matching REDIPS
row indices, reorder via array manipulation, and persist with normalized
contiguous rankings. This also auto-repairs ranking gaps on every
reorder operation.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: jbonor

ajax/reorder.php

@@ -28,8 +28,6 @@
  * -------------------------------------------------------------------------
  */
 
-use Glpi\DBAL\QueryExpression;
-
 Session::checkLoginUser();
 
 if (
@@ -49,59 +47,50 @@
 /** @var DBmysql $DB */
 global $DB;
 
-// Retrieve id of field to update
-$field_iterator = $DB->request(
+// Retrieve all fields for this container ordered by ranking.
+// Row indices from the JS drag-and-drop library (REDIPS) start at 1 (row 0 is
+// the table header), so they map to 1-based ordinal positions, not to the raw
+// ranking values stored in DB (which may contain gaps).
+$all_fields_iterator = $DB->request(
     [
         'SELECT' => 'id',
         'FROM'   => $table,
         'WHERE'  => [
             'plugin_fields_containers_id' => $container_id,
-            'ranking'                     => $old_order,
         ],
+        'ORDER'  => 'ranking ASC',
     ],
 );
 
-if (0 === $field_iterator->count()) {
-    // Unknown field
+// Build an ordered list of field IDs (1-indexed to match row indices).
+$fields = [];
+$position = 1;
+foreach ($all_fields_iterator as $row) {
+    $fields[$position] = $row['id'];
+    $position++;
+}
+
+if (!array_key_exists($old_order, $fields)) {
+    // Unknown field at given position
     throw new RuntimeException('Unknown field', 404);
 }
 
-$field_id = $field_iterator->current()['id'];
+// Remove the dragged field from its old position and re-insert at the new one.
+$field_id = $fields[$old_order];
+unset($fields[$old_order]);
+$fields = array_values($fields); // re-index to 0-based
 
-// Move all elements to their new ranking
-if ($old_order < $new_order) {
+// Convert new_order (1-based row index) to 0-based insertion index.
+$insert_index = $new_order - 1;
+array_splice($fields, $insert_index, 0, [$field_id]);
+
+// Persist the new ordering with contiguous rankings starting at 1.
+$ranking = 1;
+foreach ($fields as $id) {
     $DB->update(
         $table,
-        [
-            'ranking' => new QueryExpression($DB->quoteName('ranking') . ' - 1'),
-        ],
-        [
-            'plugin_fields_containers_id' => $container_id,
-            ['ranking'                    => ['>',  $old_order]],
-            ['ranking'                    => ['<=', $new_order]],
-        ],
-    );
-} else {
-    $DB->update(
-        $table,
-        [
-            'ranking' => new QueryExpression($DB->quoteName('ranking') . ' + 1'),
-        ],
-        [
-            'plugin_fields_containers_id' => $container_id,
-            ['ranking'                    => ['<',  $old_order]],
-            ['ranking'                    => ['>=', $new_order]],
-        ],
+        ['ranking' => $ranking],
+        ['id'      => $id],
     );
+    $ranking++;
 }
-
-// Update current element
-$DB->update(
-    $table,
-    [
-        'ranking' => $new_order,
-    ],
-    [
-        'id' => $field_id,
-    ],
-);