Fix duplicate tags creation when assigning search results to tag

Fixes #6330

src/Wallabag/CoreBundle/Controller/TagController.php

@@ -247,10 +247,15 @@ class TagController extends AbstractController
                 $filter
             );
 
+            // check to avoid duplicate tags creation
+            foreach ($this->entityManager->getUnitOfWork()->getScheduledEntityInsertions() as $entity) {
+                if ($entity instanceof Tag && strtolower($entity->getLabel()) === strtolower($filter)) {
+                    continue 2;
+                }
                 $this->entityManager->persist($entry);
             }
-
             $this->entityManager->flush();
+        }
 
         return $this->redirect($this->redirectHelper->to($request->headers->get('referer'), '', true));
     }

tests/Wallabag/CoreBundle/Controller/TagControllerTest.php

@@ -560,5 +560,12 @@ class TagControllerTest extends WallabagCoreTestCase
 
             $this->assertContains('title', $tags);
         }
+
+        $tag = $client->getContainer()
+            ->get(EntityManagerInterface::class)
+            ->getRepository(Tag::class)
+            ->findByLabelsAndUser(['title'], $this->getLoggedInUserId());
+
+        $this->assertCount(1, $tag);
     }
 }