Fixed #8926, #8252 - introduce circular reference check for location parent_id - rebased from #8253

app/Http/Controllers/LocationsController.php

@@ -67,7 +67,6 @@ public function store(ImageUploadRequest $request)
     {
         $this->authorize('create', Location::class);
         $location = new Location();
-        $location->id               = null; // This is required to make Laravels different validation work, it errors if the parameter doesn't exist (maybe a bug)?
         $location->name             = $request->input('name');
         $location->parent_id        = $request->input('parent_id', null);
         $location->currency         = $request->input('currency', '$');
@@ -132,7 +131,6 @@ public function update(ImageUploadRequest $request, $locationId = null)
             return redirect()->route('locations.index')->with('error', trans('admin/locations/message.does_not_exist'));
         }
 
-
         // Update the location data
         $location->name         = $request->input('name');
         $location->parent_id    = $request->input('parent_id', null);

app/Models/Location.php

@@ -28,7 +28,7 @@ class Location extends SnipeModel
         'address2'      => 'max:80|nullable',
         'zip'           => 'min:3|max:10|nullable',
         'manager_id'    => 'exists:users,id|nullable',
-        'parent_id'     => 'nullable|exists:locations,id|different:id',
+        'parent_id'     => 'non_circular:locations,id'
     );
 
     protected $casts = [

app/Providers/ValidationServiceProvider.php

@@ -58,6 +58,52 @@ public function boot()
         });
 
 
+        // Prevent circular references
+        //
+        // Example usage in Location model where parent_id references another Location:
+        //
+        //   protected $rules = array(
+        //     'parent_id' => 'non_circular:locations,id,10'
+        //   );
+        //
+        Validator::extend('non_circular', function ($attribute, $value, $parameters, $validator) {
+            if (count($parameters) < 2) {
+                throw new \Exception('Required validator parameters: <table>,<primary key>[,depth]');
+            }
+
+            // Parameters from the rule implementation ($pk will likely be 'id')
+            $table = array_get($parameters, 0);
+            $pk = array_get($parameters, 1);
+            $depth = (int) array_get($parameters, 2, 50);
+
+            // Data from the edited model
+            $data = $validator->getData();
+
+            // The primary key value from the edited model
+            $data_pk = array_get($data, $pk);
+            $value_pk = $value;
+
+            // If we’re editing an existing model and there is a parent value set… 
+            while ($data_pk && $value_pk) {
+
+                // It’s not valid for any parent id to be equal to the existing model’s id
+                if ($data_pk == $value_pk) {
+                    return false;
+                }
+
+                // Avoid accidental infinite loops
+                if (--$depth < 0) {
+                    return false;
+                }
+
+                // Get the next parent id
+                $value_pk = DB::table($table)->select($attribute)->where($pk, '=', $value_pk)->value($attribute);
+            }
+
+            return true;
+        });
+
+
         // Yo dawg. I heard you like validators.
         // This validates the custom validator regex in custom fields.
         // We're just checking that the regex won't throw an exception, not

resources/lang/en/validation.php

@@ -89,6 +89,7 @@
     'uploaded'             => 'The :attribute failed to upload.',
     'url'                  => 'The :attribute format is invalid.',
     "unique_undeleted"     => "The :attribute must be unique.",
+    "non_circular"         => "The :attribute must not create a circular reference.",
 
     /*
     |--------------------------------------------------------------------------