bureucracy: handle multi fields of type page with setting 'usetitles'

Addresses one of the issues in #700

Author: annda

_test/BureaucracyTest.php

@@ -7,7 +7,7 @@
 /**
  * Tests for the integration with Bureaucracy plugin
  *
- * @group plugin_structb
+ * @group plugin_struct
  * @group plugins
  *
  */

action/bureaucracy.php

@@ -115,9 +115,10 @@ public function handleLookupFields(Event $event, $param)
                     // lookups can reference pages or global data, so check both pid and rid
                     // make sure not to double decode pid!
                     $originalPid = $pid;
-                    $pid = json_decode($pid, null, 512, JSON_THROW_ON_ERROR)[0] ?? $pid;
-                    $rid = json_decode($originalPid, null, 512, JSON_THROW_ON_ERROR)[1] ?? null;
-                    if (($pid && $pids[$i] === $pid) || ($rid && $rids[$i] === (string)$rid)) {
+                    // do not throw JSON exception here, we supply alternative values if json_decode doesn't
+                    $pid = json_decode($pid, null, 512)[0] ?? $pid;
+                    $rid = json_decode($originalPid, null, 512)[1] ?? null;
+                    if (($pid && $pids[$i] === $pid) || ($rid && $rids[$i] === $rid)) {
                         $field->opt['struct_pids'][] = $pid;
                         $new_value[] = $result[$i][0]->getDisplayValue();
                     }

helper/field.php

@@ -158,14 +158,19 @@ public function replacementMultiValueCallback($matches)
      */
     protected function createValue()
     {
-        $preparedValue = $this->opt['value'] ?? '';
+        // input value or appropriately initialized empty value
+        $preparedValue = $this->opt['value'] ?? ($this->column->isMulti() ? [] : '');
 
         // page fields might need to be JSON encoded depending on usetitles config
         if (
             $this->column->getType() instanceof Page
             && $this->column->getType()->getConfig()['usetitles']
         ) {
-            $preparedValue = json_encode([$preparedValue, null], JSON_THROW_ON_ERROR);
+            if ($this->column->isMulti()) {
+                $preparedValue = array_map(static fn($val) => json_encode([$val, null], JSON_THROW_ON_ERROR), $preparedValue);
+            } else {
+                $preparedValue = json_encode([$preparedValue, null], JSON_THROW_ON_ERROR);
+            }
         }
 
         $value = new Value($this->column, $preparedValue);