Fix TagList formwidget (#1267)

The TagList formwidget was not working properly in relation mode if the relation was not using a pivot table (e.g. morphMany/hasMany)

All modes did not update the model field or relation when all tags had been cleared.

Fixes #1223

modules/backend/formwidgets/TagList.php

@@ -4,6 +4,8 @@
 
 use Backend\Classes\FormWidgetBase;
 use Illuminate\Database\Eloquent\Relations\Relation as RelationBase;
+use Winter\Storm\Database\Relations\BelongsToMany;
+use Winter\Storm\Database\Relations\MorphToMany;
 
 /**
  * Tag List Form Widget
@@ -125,29 +127,46 @@ public function getSaveValue($value)
      */
     protected function hydrateRelationSaveValue($names): ?array
     {
-        if (!$names) {
-            return $names;
-        }
-
         if (!is_array($names)) {
             $names = [$names];
         }
 
+        $names = array_filter($names);
+
+        $relation = $this->getRelationObject();
         $relationModel = $this->getRelationModel();
-        $existingTags = $relationModel
-            ->whereIn($this->nameFrom, $names)
-            ->lists($this->nameFrom, $relationModel->getKeyName())
-        ;
+
+        $keyName = $relationModel->getKeyName();
+        $pivot = in_array(get_class($relation), [BelongsToMany::class, MorphToMany::class]);
+
+        if ($pivot) {
+            $existingTags = $relationModel->whereIn($this->nameFrom, $names)->lists($this->nameFrom, $keyName);
+        } else {
+            $existingTags = $relation->lists($this->nameFrom, $keyName);
+        }
 
         $newTags = $this->customTags ? array_diff($names, $existingTags) : [];
+        $deletedTags = $this->customTags ? array_diff($existingTags, $names) : [];
 
         foreach ($newTags as $newTag) {
-            $newModel = new $relationModel;
-            $newModel->{$this->nameFrom} = $newTag;
-            $newModel->save();
+            if ($pivot) {
+                $newModel = new $relationModel;
+                $newModel->{$this->nameFrom} = $newTag;
+                $newModel->save();
+            } else {
+                $newModel = $relation->create([$this->nameFrom => $newTag]);
+            }
             $existingTags[$newModel->getKey()] = $newTag;
         }
 
+        if (!$pivot && $deletedTags) {
+            $deletedKeys = array_keys($deletedTags);
+            $relation->whereIn($keyName, $deletedKeys)->delete();
+            foreach ($deletedTags as $id) {
+                unset($existingTags[$id]);
+            }
+        }
+
         return array_keys($existingTags);
     }
 

modules/backend/formwidgets/taglist/partials/_taglist.php

@@ -33,6 +33,7 @@
             value="<?= $field->value ?>">
     <?php endif ?>
 <?php else: ?>
+    <input type="hidden" name="<?= $field->getName() ?>[]">
     <select
         id="<?= $field->getId() ?>"
         name="<?= $field->getName() ?>[]"